Astronomy Picture of the Day Search Results for "venus"

APOD: 2009 March 14 - Haute Provence Star Trails
Explanation: Fix your camera to a tripod and you can record the graceful trails traced by the stars as planet Earth rotates on its axis. For example, this dramatic 5 hour long exposure was made on February 24 from Haute-Provence Observatory (OHP) in southeastern France. Actually a composite of 300 consecutive 1-minute exposures, the image nicely shows stars near the celestial equator tracing nearly straight lines in projection, while stars north and south of the equator, respectively, appear to circle the north and south celestial poles. Domes at the bottom left and right house the OHP telescopes. Brilliant planet Venus makes the short bright trail at the lower right, while trails of stars in the end near the lower right observatory dome. Sirius, alpha star of Canis Major, traces the bright arc over the dome at the left. Astronomer Alexandre Santerne also briefly illuminated a foreground oak tree during the exposure sequence.

APOD: 2009 March 6 - Crescent Moon and Venus
Explanation: Last Friday, the Moon and Venus shared the early evening sky in a beautiful conjunction. Separated by only about 2 degrees, they also were both in a crescent phase. Just like our Moon, Venus can appear as a full disk or a thin crescent. Frequently the brightest object in the post-sunset or pre-sunrise sky, Venus is so small that it usually requires binoculars or a small telescope to clearly see its phase. This telescopic image of Friday's conjunction shows off the similar crescent phases, with the tiny crescent Venus at the upper right.

APOD: 2009 February 12 - Zodiacal Light Vs. Milky Way
Explanation: Two fundamental planes of planet Earth's sky compete for attention in this remarkable wide-angle vista, recorded on January 23rd. Arcing above the horizon and into the night at the left is a beautiful band of Zodiacal Light - sunlight scattered by dust in the solar system's ecliptic plane. Its opponent on the right is composed of the faint stars, dust clouds, and nebulae along the plane of our Milky Way Galaxy. Both celestial bands stand above the domes and towers of the Teide Observatory on the island of Tenerife. Also out to play in the pristine, dark skies over the Canary Islands, are brilliant Venus (lower left), the distant Andromeda Galaxy (near center), and the lovely Pleiades star cluster (top center). Of course, seasoned skygazers might even spot M33, the California Nebula, IC1805, and the double star cluster of Perseus. (Need some help? Just slide your cursor over the picture.)

APOD: 2009 February 4 - A Dangerous Summer on HD 80606b
Explanation: On the distant planet HD 80606b, summers might be dangerous. Hypothetic life forms floating in HD 080606b's atmosphere or lurking on one of its (presently hypothetical) moons might fear the 1,500 Kelvin summer heat, which is hot enough not only to melt lead but also nickel. Although summers are defined for Earth by the daily amount of sunlight, summers on HD 80606b are more greatly influenced by how close the planet gets to its parent star. HD 80606b, about 200 light years distant, has the most elliptical orbit of any planet yet discovered. In comparison to the Solar System, the distance to its parent star would range from outside the orbit of Venus to well inside the orbit of Mercury. In this sequence, the night side of HD 80606b is computer simulated as it might glow in infrared light in nearly daily intervals as it passed the closest point in its 111-day orbit around its parent star. The simulation is based on infrared data taken in late 2007 by the Spitzer Space Telescope.

APOD: 2009 January 2 - Alpine Conjunction
Explanation: Did you see it? The last conjunction of Moon and bright planets in 2008 featured a young crescent Moon and brilliant Venus in the west after sunset on December 31st. Seen here in dark, clear, mountain air from Mönichkirchen, Austria, are the two celestial beacons that dominate planet Earth's night sky. That pair was hard to miss, but skygazers watching lower along the western horizon in early twilight might also have glimpsed a pairing of Jupiter and Mercury as they both wandered closer to the Sun in the sky at year's end. Still, while this single, 5 second long exposure seriously overexposes the Moon's sunlit crescent, it does capture another planet not visible to the unaided eye. The tiny pinprick of light just above the photographer's head in the picture is the distant planet Neptune.

APOD: 2009 January 1 - Welcome to the International Year of Astronomy
Explanation: Astronomers all over planet Earth invite you to experience the night sky as part of the International Year of Astronomy 2009. This year was picked by the International Astronomical Union and the United Nations Educational, Scientific, and Cultural Organization because it occurs 400 years after Galileo turned one of the first telescopes toward the heavens. Peering through that small window, Galileo discovered that the Moon has craters, Venus has phases, Jupiter has moons, and Saturn has rings. This year you can discover these and many modern wonders of the amazing overhead tapestry that is shared by all of humanity. If, like many others, you find the night sky wondrous and educational, be sure to attend an IYA2009 event in your area, and tell any schools and children that might be interested. Also, please feel free to explore the extensive IYA2009 web pages to find international media events that include blogs, webcasts and much much more.

APOD: 2008 December 13 - The 60 inch Reflector
Explanation: On the night of December 13, 1908, 100 years ago today, the 60-inch diameter reflecting telescope of Mount Wilson Observatory was first tested on the stars. It became the first successful large reflecting telescope. The 60-inch reflector demonstrated a scalable design that used a mirror to gather faint starlight, rather than a large and more difficult to support lens, becoming the granddaddy of all, even larger, modern telescopes. Now-famous astronomers, including Harlow Shapley and Edwin Hubble, were able to use the 60-inch reflector to embark on a new kind of exploration of stars, distant galaxies, and the nature of the universe. Still looking skyward a century after its first light, the historic telescope is seen here pointing toward one of the most recognizable celestial events of 2008, the remarkable conjunction of Moon, Venus, and Jupiter.

APOD: 2008 December 6 - Lunar Diamond
Explanation: Cameras around the globe pointed skyward this week to capture the spectacular conjunction of a crescent Moon and bright planets Venus and Jupiter. But astronomer-artist Deirdre Kelleghan recorded her observations in sketches of the celestial event. From Greystones, County Wicklow, Ireland, her small telescope allowed her to follow the accompanying lunar occultation as a brilliant Venus disappeared behind the Moon's dark edge, then reappeared along the bright lunar limb. Her lovely drawing of the reemergence of Venus was made with pastels and conte crayons on A3 size paper under very cold conditions. She remarks, "The view as Venus once again sparkled like a diamond stuck on the moon was stunning."

APOD: 2008 December 5 - Smile in the Sky
Explanation: At sunset, Monday's western sky showed off stunning colors and dramatic clouds reflected in Brisbane Water on the Central Coast of New South Wales, Australia. It also featured the remarkable conjunction of the crescent Moon, Venus, and Jupiter forming a twilight smiley face. While the gathering of the two bright planets and Moon awed skygazers around planet Earth, astronomer Mike Salway reports taking special pains to record this gorgeous view, braving mosquitos and rain squalls along a soggy shore. His southern hemisphere perspective finds brilliant Venus at the highest point in the celestial grouping. For now, a bright pairing of Venus and Jupiter continues to dominate the western horizon after sunset but the Moon has moved on and tonight is near its first quarter phase.

APOD: 2008 December 4 - Venus in the Moon
Explanation: On December 1, bright planets Venus and Jupiter gathered near the young crescent Moon, an inspiring celestial scene in early evening skies around the world. But from some locations the Moon actually passed in front of Venus, interrupting the tight grouping with a lunar occultation. Captured from Wildon, Austria, this twilight view shows the silvery evening star about five minutes before it slipped behind the dark lunar limb and vanished from sight for more than hour. The image is a combination of long and short exposures showing details of the lunar surface illuminated by both faint earthshine and bright sunlight. In the inset, recorded later in darkened skies over Breil-sur-Roya in southeastern France, a dazzling Venus has reappeared below the bright lunar crescent. Of course, Jupiter, at the upper right about 2 degrees from Venus and Moon, is sporting moons of its own seen as tiny pinpricks of light on either side of the bright planet.

APOD: 2008 December 3 - A Happy Sky Over Los Angeles
Explanation: Sunday, the sky seemed to smile over much of planet Earth. Visible the world over was an unusual superposition of our Moon and the planets Venus and Jupiter. Pictures taken at the right time show a crescent Moon that appears to be a smile when paired with the planetary conjunction of seemingly nearby Jupiter and Venus. Pictured above is the scene as it appeared from Mt. Wilson Observatory overlooking Los Angeles, California, USA after sunset on 2008 November 30. Highest in the sky and farthest in the distance is the planet Jupiter. Significantly closer and visible to Jupiter's lower left is Venus, appearing through Earth's atmospheric clouds as unusually blue. On the far right, above the horizon, is our Moon, in a waxing crescent phase. Thin clouds illuminated by the Moon appear unusually orange. Sprawling across the bottom of the image are the hills of Los Angeles, many covered by a thin haze, while LA skyscrapers are visible on the far left. The conjunction of Venus and Jupiter will continue to be visible toward the west after sunset during much of this month. Hours after the taking of this image, however, the Moon approached the distant duo, briefly eclipsed Venus, and then moved on.

APOD: 2008 November 29 - Chilean Skyscape
Explanation: Night skies over Chilean mountain top observatories can be dark and clear, with glorious cosmic vistas. In this recent example, the plane of our Milky Way galaxy stretches parallel to the horizon, the galactic center's star clusters, dark dust clouds, and glowing nebulae hovering in the west. Recorded after sunset, the wedge of light extending upward through the scene is Zodiacal light, sunlight scattered by dust along the solar system's ecliptic plane. A faint meteor was also caught in the view, but approaching a conjunction, brilliant Venus and bright Jupiter dominate the skyscape. A close pairing through this weekend, by Monday, December 1, they will be joined by the young crescent Moon. Look west after sunset and the tight celestial triangle formed by Moon, Venus, and Jupiter, the three brightest beacons in the night, will be a spectacular sight, even from bright-sky urban locations all over the world.

APOD: 2008 September 30 - Planets Ahoy
Explanation: Can you spot the Solar System's four rocky planets? In the above image taken on September 20, all of them were visible in a single glance, but some of them may be different than you think. Pictured above, the brightest and highest object in the sky is the planet Venus. The object lowest in the sky is the planet Mars, while the object furthest to the left is the planet Mercury. The last remaining point of light is . . . the bright star Spica, which leaves the question -- where is the fourth rocky planet? That would be Earth, specifically part of Australia, visible across the entire bottom of the image.

APOD: 2008 September 25 - The Case of the Very Dusty Binary Star
Explanation: For astronomers, close binary star system BD+20 307 originally stood out because it is extremely dusty. A substantial amount of warm dust surrounding it causes the system to appear exceptionally bright at infrared wavelengths. Of course, dust associated with planet formation is often detected around young stars, stars only a few million years old. But the BD+20 307 system has now been found to be at least a few billion years old, an age comparable to the age of our own Solar System. The large amount of warm dust is likely the debris from a relatively recent collision of planet-sized objects on the scale of, say, Earth and Venus, in the BD+20 307 system. Reminiscent of the classic scifi novel When Worlds Collide, the dramatic illustration offers a depiction of the catastrophic event. Ironically, this indirect evidence of a destructive planetary collision could also be the first indication that planetary systems can form around close binary stars. BD+20 307 is about 300 light-years distant toward the headstrong constellation Aries.

APOD: 2008 September 15 - SN 1006: A Supernova Ribbon from Hubble
Explanation: What created this unusual space ribbon? Most assuredly, one of the most violent explosions ever witnessed by ancient humans. Back in the year 1006 AD, light reached Earth from a stellar explosion in the constellation of the Wolf (Lupus), creating a "guest star" in the sky that appeared brighter than Venus and lasted for over two years. The supernova, now cataloged at SN 1006, occurred about 7,000 light years away and has left a large remnant that continues to expand and fade today. Pictured above is a small part of that expanding supernova remnant dominated by a thin and outwardly moving shock front that heats and ionizes surrounding ambient gas. SN 1006 now has a diameter of nearly 60 light years. Within the past year, an even more powerful explosion occurred far across the universe that was visible to modern humans, without any optical aid, for a few seconds.

APOD: 2008 September 12 - Planets over Perth
Explanation: A bright trio of terrestrial planets was joined by a young Moon on September 1st, in planet Earth's early evening skies. In this view of the celestial gathering from Perth, Western Australia, the Moon's sunlit crescent is nearly horizontal at Perth's southern latitude of about 32 degrees. Venus, then Mercury, and finally Mars shine above colorful city lights on the far shore of the Swan River. The six unlit towers on the left surround a large cricket stadium. For now, the planetary trio still lingers low in the west just after sunset. But in the coming days Venus will move farther from the Sun, climbing higher after sunset, while Mercury and Mars will steadily sink into the glare along the western horizon.

APOD: 2008 August 21 - August Moons
Explanation: This August was eclipse season. The month's first New Moon and Full Moon were both seen in darkened skies during a solar and lunar eclipse. Blocking the Sun, the left panel's New Moon was captured during the total solar eclipse of August 1 from the path of totality overlooking Novosibirsk (Siberia) Reservoir, locally known as the Ob Sea. A lovely solar corona and bright inner planets Mercury and Venus emerged during the total eclipse phase, while the flickering view screens of eclipse watchers' digital cameras dotted the landscape. On the right, the Full Moon grazed Earth's shadow nearly 15 days later in a partial lunar eclipse. That serene view was recorded during an early evening stroll along the shores of the Odet River near the city of Quimper in western France. For planet Earth there are about two seasons each year during which the orientation of the Moon's orbit is favorable for solar and lunar eclipses. The next eclipse season begins in January 2009 with an annular solar eclipse.

APOD: 2008 August 5 - A Total Solar Eclipse Over China
Explanation: What's that black dot over the Sun? The Moon. This past weekend, the Sun went dark during the day as the Moon completely covered it. The total solar eclipse was visible over a thin swath of Earth extending from northern Canada to China. As shown above, many sky enthusiasts gathered to witness the total or partial solar eclipse, which lasted only a few minutes. The above image was taken during totality near Barkol in Xinjiang, China, with the Barkol Shan mountain range visible on the horizon. Although the brightest parts of the Sun are covered, the normally invisible corona of hot gas surrounding the Sun became prominent. Just to the upper left of the Moon darkened Sun are planets Mercury and Venus. The increased darkening of the sky toward the right indicates the darkened atmosphere created by the passing shadow cone of the total solar eclipse. The next total solar eclipse will occur next July and be visible in parts of India and China.

APOD: 2008 April 23 - Above the Clouds
Explanation: From the windswept peak of Mauna Kea, on the Big Island of Hawaii, your view of the world at night could look like this. At an altitude of about 13,500 feet, the mountain top is silhouetted in the stunning skyscape recorded near dusk in early December of 2005. The volcanic peak rises just above a sea of storm clouds illuminated by a bright Moon. Planet Venus is setting near the Moon as the brilliant evening star. The scene also includes the faint, milky band of our own galaxy's disk of stars and cosmic dust clouds stretching from the horizon into the sky along the right edge of the frame.

APOD: 2008 March 10 - Planets Align Over Australian Radio Telescope Array
Explanation: Last week, Mercury, Venus, and the Moon all appeared close together in Earth's sky. This picturesque conjunction was caught on camera behind elements of the Australia Telescope Compact Array (ATCA) near the town of Narrabri in rural New South Wales. The ATCA consists of six radio telescopes in total, each one larger than a house. Together they form one of the highest resolution measurement devices in the world. Impressive planetary conjunctions occur every few years. Involving the brightest objects in the night sky, this alignment was easy to spot just before sunrise. In the picture, taken on the morning of March 6, Mercury is the highest of the three bright celestial beacons.

APOD: 2008 February 26 - Mysterious Acid Haze on Venus
Explanation: Why did an acidic haze spread across Venus? The unusual clouds were discovered last July by ESA's robotic Venus Express spacecraft currently orbiting Venus. The bright and smooth haze was found by Venus Express to be rich in sulfuric acid, created when an unknown process lifted water vapor and sulphur dioxide from lower levels into Venus' upper atmosphere. There, sunlight broke these molecules apart and some of them recombined into the volatile sulfuric acid. Over the course of just a few days last July, the smooth acidic clouds spread from the South Pole of Venus across half the planet. The above false-color picture of Venus was taken last July 23rd in ultraviolet light, and shows the unusual haze as relatively smooth regions across the image bottom. The cause of the dark streaks in the clouds is also not yet understood and is being researched.

APOD: 2008 February 2 - Venus and Jupiter in Morning Skies
Explanation: These two celestial beacons shining brightly in the east before sunrise are actually children of the Sun, the planets Venus and Jupiter. The second and third brightest objects in the sky at Night after the Moon, Venus and Jupiter appeared separated by about 2 degrees when this picture was taken on January 30th, but closed to within nearly half a degree early yesterday morning. In the serene foreground is the shoreline along the Miankaleh Peninsula and Gorgan Bay, an important bird and wildlife refuge in the southeastern Caspian Sea. Over the next two days, early morning risers around the globe will be able to enjoy a close pairing of Venus and Jupiter with an old crescent Moon.

APOD: 2007 December 8 - Star Trails at Dawn
Explanation: Just fix your camera to a tripod and you too can make an image of graceful trails traced by the stars as planet Earth rotates on its axis. Made on September 14 from Montlaux, France, this wide-angle view nicely shows the stars near the celestial equator tracing nearly straight lines in projection, while stars north and south of the equator, respectively, appear to circle the north and south celestial poles. Featured are the stars of Orion (right of center), brilliant Venus rising (left) as bright star Sirius rises in the south (bottom center), and a polar orbiting Iridium satellite (upper left). Beautiful dawn sky colors seem painted along the horizon. This remarkable picture was constructed from 477 consecutive 30 second digital exposures recorded over 4.3 hours and later combined.

APOD: 2007 November 8 - VERITAS and Venus
Explanation: Early morning risers and late to bed astronomers have recently enjoyed bright planets in predawn skies, with brilliant Venus above the eastern horizon. On November 5, Venus was joined by the waning crescent Moon. This self-portrait by astronomer Larry Ciupik captures the lovely pairing of the two brightest celestial beacons on the scene, though the Moon, right of Venus, is strongly over exposed. Included at the far left in the 30 second exposure is the bright streak of the International Space Station still docked with shuttle orbiter Discovery. Together in Earth orbit, the spacefaring combination was momentarily the third brightest sky light in view. In dim silhouette, a multi-mirrored unit of the Very Energetic Radiation Imaging Telescope Array System (VERITAS) is also visible in the foreground. VERITAS operates at the Whipple Observatory near Tucson, Arizona to detect high-energy gamma-rays from the cosmos.

APOD: 2007 October 11 - Bright Planets, Crescent Moon
Explanation: Early risers are currently enjoying the sight of dazzling Venus, near the eastern horizon as the morning star. Recorded on October 7, this predawn skyview does feature Venus at the upper right. It also includes a crescent Moon and Saturn (lower left). In fact, holding your fist at arms length would have easily covered both planets and the Moon in this 5 degree wide field. Earthshine, sunlight reflected from planet Earth's dayside, illuminates features on the lunar nightside. A close inspection of Saturn itself reveals a nearby pinpoint of light corresponding to Saturn's large moon Titan. Though the Moon has moved on, the tight triangle formed by Venus, Saturn, and Regulus (top), alpha star in the constellation Leo, will continue to look impressive in early morning skies over the next few days. Early bird astrophotographer Jay Ouellet also described Mars as a "brilliant red diode" in his dark country sky east of Quebec City, Canada.

APOD: 2007 October 2 - Tutulemma: Solar Eclipse Analemma
Explanation: If you went outside at exactly the same time every day and took a picture that included the Sun, how would the Sun appear to move? With great planning and effort, such a series of images can be taken. The figure-8 path the Sun follows over the course of a year is called an analemma. With even greater planning and effort, the series can include a total eclipse of the Sun as one of the images. Pictured is such a total solar eclipse analemma or Tutulemma - a term coined by the photographers based on the Turkish word for eclipse. The composite image sequence was recorded from Turkey starting in 2005. The base image for the sequence is from the total phase of a solar eclipse as viewed from Side, Turkey on 2006 March 29. Venus was also visible during totality, toward the lower right.

APOD: 2007 July 18 - Planets over Pony Express Lake
Explanation: Beautiful sunset sky colors are reflected in Pony Express Lake in this twilight skyview from northern Missouri, USA, planet Earth. Recorded on Monday, a two day old crescent Moon and brilliant planet Venus shine through thin clouds. Joining the conjunction on the right of the Moon's sunlit crescent is fellow wanderer Saturn, with Regulus, alpha star of the constellation Leo, above and right of Venus. Moonlight and Venus light streak the almost-calm lake waters.

APOD: 2007 July 4 - Red, White, and Blue Sky
Explanation: Contrasting colors in this beautiful sunset sky were captured on June 30 from Clear Creek Canyon Observatory in central Arizona, USA. The twilight scene includes brilliant Venus as the evening star, with a bright Saturn just above it, shining through thin clouds. The two wandering planets were a mere 1 degree apart or so, about twice the width of the full Moon rising above the eastern horizon on the other side of the sky. In fact, such serene skyviews were possible from all over planet Earth as Venus and Saturn approached a conjunction. Regulus, alpha star of the constellation Leo, is above and to the left of the close planetary pairing. At dusk, lights in tonight's sky will also feature Venus and Saturn low in the west and separated by about 2 degrees.

APOD: 2007 June 20 - A Daylight Eclipse of Venus
Explanation: Something was about to happen. Just two days ago, two of the three celestial objects easily visible during the day appeared to collide. But actually, Earth's Moon passed well in front of the distant planet Venus. The occultation was caught from Switzerland in the hours before sunset. Moments after this image was taken, the Moon, visible as the crescent on the right of the above image, eclipsed Venus, appearing near half phase on the lower left. Clouds that once threatened to obscure the whole event, were visible on the far left. About 90 minutes later, Venus re-appeared just to the right of the bright crescent.

APOD: 2007 May 26 - The Moon's Saturn
Explanation: On May 22nd, just days after sharing the western evening sky with Venus, the Moon moved on to Saturn - actually passing in front of the ringed planet when viewed in skies over Europe, northern Africa, and western Asia. Because the Moon and bright planets wander through the sky near the ecliptic plane, such occultation events are not uncommon, but they are dramatic, especially in telescopic views. For example, in this sharp image Saturn is captured emerging from behind the Moon, giving the illusion that it lies just beyond the Moon's bright edge. Of course, the Moon is a mere 400 thousand kilometers away, compared to Saturn's distance of 1.4 billion kilometers. Taken with a digital camera and 20 inch diameter telescope at the Weikersheim Observatory in southern Germany, the picture is a single exposure adjusted to reduce the difference in brightness between Saturn and the cratered lunar surface.

APOD: 2007 May 23 - Venus Near the Moon
Explanation: The two brightest objects in the night sky appeared to go right past each other last week. On the night of May 19, Earth's Moon and the planet Venus were visible in the same part of the sky, and at closest approach were less than one degree apart. The conjunction was captured in the above image taken from near Quebec City, Quebec, Canada. Venus appears on the lower left of the above photo. The spires that appear to emanate from Venus are diffraction spikes caused by the camera itself. The image is so clear that craters on the Moon are resolved. Of course, the real physical distance between the two heavenly bodies was not unusually small -- the apparent conjunction was really just an illusion of perspective. Although Earth's Moon passes Venus once each month, such a close passing visible in the evening sky is more rare.

APOD: 2007 May 4 - The Iron Tail of Comet McNaught
Explanation: Outstanding in planet Earth's sky early this year, Comet McNaught is captured in this view from the STEREO A spacecraft. McNaught's coma is so bright, it blooms into the long horizontal stripe at the bottom of the field. Brilliant Venus, near the top left corner, also produces a severe horizontal blemish in the digital image. But the sensitive camera does accurately record the striations in McNaught's famous dust tail along a region stretching over 30 million kilometers toward the top right of the field of view. A separate, fainter, arching tail just to the left of the dust tail was initially thought to be an example of a common ion tail, formed by electrically charged atoms carried away from the comet by the solar wind. However, detailed modeling indicates that tail is actually due to neutral iron atoms pushed out by the pressure of sunlight -- the first ever detected neutral iron tail from a comet. The iron atoms are thought to originate in dust grains from the comet nucleus that contain the iron-sulfur mineral troilite (FeS).

APOD: 2007 May 2 - Sunrise from the Surface of Gliese 581c
Explanation: How might a sunrise appear on Gliese 581c? One artistic guess is shown above. Gliese 581c is the most Earth-like planet yet discovered and lies a mere 20 light-years distant. The central red dwarf is small and redder than our Sun but one of the orbiting planets has recently been discovered to be in the habitable zone where liquid water could exist on its surface. Although this planet is much different from Earth, orbiting much closer than Mercury and containing five times the mass of Earth, it is now a candidate to hold not only oceans but life enabled by the oceans. Were future observations to confirm liquid water, Gliese 581c might become a worthy destination or way station for future interstellar travelers from Earth. Drawn above in the hypothetical, the red dwarf star Gliese 581 rises through clouds above a calm ocean of its planet Gliese 581c.

APOD: 2007 May 1 - Swirling Clouds Over the South Pole of Venus
Explanation: What's happening over the South Pole of Venus? To find out, scientists sent the robot Venus Express spacecraft now orbiting Venus directly over the lower spin axis of Earth's overheated twin. Venus Express confirmed there a spectacular massive swirling storm system with similarities to the vortex recently imaged over Saturn's South Pole. The above composite image in infrared light features Venus' daytime side on the left, shining primarily by reflected sunlight, and nighttime side on the right, shining primarily by thermal light. A Venusian polar vortex is visible as the small circular feature near the center of the thermal infrared image pictured on the right. Close inspection of other South Pole images unexpectedly showed a second vortex, meaning that the unusual swirling clouds are like an Earth-hurricane that has two eyes. Why a double vortex has formed is now a topic of research. The above image was taken last year, and more recent images from Venus Express are being processed that have as much as 100 times more detail.

APOD: 2007 April 28 - Young Moon and Sister Stars
Explanation: A young crescent Moon shared the western sky with thin clouds and the sister stars of the Pleiades cluster in this early evening skyscape recorded on April 19th. Astronomical images of the well-known Pleiades often show the star cluster's alluring blue reflection nebulae, but they are washed-out here in the clouds and bright moonlight. While the 3-day old Moon is overexposed, surface features can be seen on the dim lunar night side, illuminated by earthshine - light from sunlit planet Earth. Only a week earlier, brilliant Venus also posed near the sister stars. Of course, Venus has not yet wandered too far from the Pleiades and still rules western skies as the evening star.

APOD: 2007 April 14 - Venus by the Lake
Explanation: Finding Venus in the night sky is not too hard these days. Now appearing as the evening star, Venus rules as the brightest celestial beacon in west just after sunset. And if you can find Venus tonight, you can also easily find the lovely Pleiades star cluster (aka M45) close by. In this serene skyview, recorded on Tuesday near Bolu, Turkey, Venus and the Pleiades are on the right, with brilliant Venus reflected in the calm waters of the small lake in the foreground. Left of Venus, the bright star Aldebaran anchors the V-shaped Hyades star cluster. Farther left are stars of the familiar constellation Orion with Rigel, at the foot of Orion, also reflected in the lake. Meanwhile, Sirius, in Canis Major, is the brightest star on the left side of the view. But the bright terrestrial light below Sirius is not a reflection, it's just a light near the lake shore.

APOD: 2007 March 24 - Lisbon Moonset
Explanation: Brilliant Venus, a slender crescent Moon, and lights along the Ponte 25 de Abril glow against the western twilight in this lovely moonset scene from Lisbon, Portugal, recorded on March 20. In fact, such serene views were enjoyed across planet Earth this week, as the young Moon remained near the setting Sun following a partial solar eclipse, and Venus ruled as the evening star. Because of strong Earthshine - light from the sunlit Earth - even the Moon's night side is clearly visible in the picture. The Ponte 25 de Abril is a 2.3 kilometer long suspension bridge across the Tagus river, often compared to the Golden Gate bridge in San Francisco, USA.

APOD: 2007 January 27 - Castle and Sky
Explanation: While Comet McNaught ruled southern skies, last week's conjunction of the Moon and Venus could be enjoyed by denizens of both hemispheres of planet Earth. The two more commonly viewed celestial beacons produced this lovely twilight scene, recorded last Saturday in skies above Almodovar near Cordoba in southern Spain. Brilliant Venus and a slender crescent Moon seem to overlook the small town, along with a well-lit Castle Almodovar. The impressive castle's construction began in the 700s on the strategic site of a Roman fort. It was extensively restored in the 20th century.

APOD: 2007 January 15 - Comet McNaught Over Catalonia
Explanation: This past weekend Comet McNaught peaked at a brightness that surpassed even Venus. Fascinated sky enthusiasts in the Earth's northern hemisphere were treated to an instantly visible comet head and a faint elongated tail near sunrise and sunset. Recent brightness estimates had Comet McNaught brighter than magnitude -5 (minus five) over this past weekend, making it the brightest comet since Comet Ikeya-Seki in 1965, which was recorded at -7 (minus seven). The Great Comet of 2007 reached its brightest as it rounded the Sun well inside the orbit of Mercury. Over the next week Comet McNaught will begin to fade as it moves south and away from the Sun. The unexpectedly bright comet should remain visible to observers in the southern hemisphere with unaided eyes for the rest of January. The above image, vertically compressed, was taken at sunset last Friday from mountains above Catalonia, Spain.

APOD: 2006 December 9 - Three Planets in Dawn Skies
Explanation: Three children of the Sun rise in the east in this peaceful dawn skyview recorded December 7th near Bolu, Turkey. Inner planet Mercury, fresh from its second transit of the 21st century, stands highest in the bright sky at the top right. Gas giant Jupiter lies below the cloud bank near picture center. A newsworthy Mars is also visible, right of Jupiter and just above the dark cloud bank. On Sunday, these planets will form a much tighter grouping before sunrise, while in the coming days the western sky after sunset will be ruled by brilliant planet Venus, also known as the evening star.

APOD: 2006 November 16 - Children of the Sun
Explanation: For a moment, planets Jupiter, Venus, Mars, and Mercury all posed near their parent star in this Sun-centered view, recorded on November 11. The picture, from a coronograph onboard the space-based SOlar Heliospheric Observatory, spans 15 degrees with the Sun's size and position indicated by the white circle. Background stars are also visible as the otherwise overwhelming sunlight is blocked by the coronograph's occulting disk. But the planets themselves, in particular Jupiter and Venus, are still bright enough to cause significant horizontal streaks in the image. Mercury is actually moving most rapidly (left to right) through the field and days earlier was seen to cross in front of the solar disk. So what's that bright double star to the left of Mars? Zubenelgenubi, of course.

APOD: 2006 November 8 - Simulated Transit of Mercury
Explanation: Mercury, the solar system's innermost planet, will spend about five hours crossing in front of the Sun today - beginning at 1912 UT (2:12pm EST), November 8. Specially equipped telescopes are highly recommended to safely spot the planet's diminutive silhouette however, as Mercury should appear about 200 times smaller than the enormous solar disk. This simulated view is based on a filtered solar image recorded on November 3rd. It shows active regions and the Mercury transit across the Sun at six positions from lower left to middle right. Depending on your location, the Sun may not be above the horizon during the entire transit, but webcasts of the event are planned - including one using images from the sun-staring SOHO spacecraft. This is the second of 14 transits of Mercury during the 21st century. The next similar event will be a transit of Venus in June of 2012.

APOD: 2006 October 30 - Crescent Venus and Moon
Explanation: There's something behind these clouds. Those faint graceful arcs, upon inspection, are actually far, far in the distance. They are the Earth's Moon and the planet Venus. Both the Moon and Venus are bright enough to be seen during the day, and both are quite capable of showing a crescent phase. To see Venus, which appears quite small, in a crescent phase requires binoculars or a telescope. In the above dramatic daytime image taken from Budapest, Hungary, the Moon and Venus shared a similar crescent phase a few minutes before the Moon eclipsed the larger but more distant world. About an hour later, Venus reappeared.

APOD: 2006 August 28 - Eight Planets and New Solar System Designations
Explanation: How many planets are in the Solar System? This popular question now has a new formal answer according the International Astronomical Union (IAU): eight. Last week, the IAU voted on a new definition for planet and Pluto did not make the cut. Rather, Pluto was re-classified as a dwarf planet and is considered as a prototype for a new category of trans-Neptunian objects. The eight planets now recognized by the IAU are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Solar System objects now classified as dwarf planets are: Ceres, Pluto, and the currently unnamed 2003 UB313. Planets, by the new IAU definition, must be in orbit around the sun, be nearly spherical, and must have cleared the neighborhood around their orbits. The demotion of Pluto to dwarf planet status is a source of continuing dissent and controversy in the astronomical community.

APOD: 2006 July 23 - The Belt of Venus over the Valley of the Moon
Explanation: Although you've surely seen it, you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly off-color, slightly pink. Called the Belt of Venus, this off-color band between the dark eclipsed sky and the blue sky can be seen in nearly every direction including that opposite the Sun. Straight above, blue sky is normal sunlight reflecting off the atmosphere. In the Belt of Venus, however, the atmosphere reflects light from the setting (or rising) Sun which appears more red. The Belt of Venus can be seen from any location with a clear horizon. Pictured above, the Belt of Venus was photographed above morning fog in the Valley of the Moon, a famous wine-producing region in northern California, USA. The belt is frequently caught by accident in other photographs.

APOD: 2006 July 17 - Venus Express Arrives at Venus
Explanation: Humanity now has a spacecraft orbiting Venus. The robotic Venus Express spacecraft launched by the European Space Agency in 2005 November arrived at Venus in 2006 April. Venus Express is now orbiting Earth's sister planet and returning pictures. Pictured above is a false-color, time-lapse movie in ultraviolet light captured by the Venus Express spacecraft as it flew over Venus' northern hemisphere in late May. Venus Express is scheduled to orbit Venus for three years and collect data that might help in answering questions that include why Venus continually generates hurricane-force winds, why Venus became so hot in the past, and if there is any current volcanic activity on Venus. It is hoped that a better understanding of Venus's hot and inhospitable climate will help humanity better understand Earth's climate as well.

APOD: 2006 June 29 - Old Moon and Sister Stars
Explanation: An old crescent Moon shares the eastern sky over Menton, France with the sister stars of the Pleiades cluster in this early morning skyscape recorded just last Friday, June 23rd. (Bright Venus was also near the eastern horizon, but is not pictured here.) Astronomical images of the well-known Pleiades often show the cluster's alluring blue reflection nebulae, but they are washed out here by the bright moonlight. Still, while the crescent Moon is overexposed, surface features can be seen on the dim lunar night side illuminated by earthshine - light from sunlit planet Earth. Of course, you can spot a young crescent Moon in the early evening sky tonight. Having left the Pleiades behind, a lovely lunar crescent now appears in the west, lining up with planets Mars, Saturn, and Mercury along the solar system's ecliptic plane.

APOD: 2006 June 15 - Gordel van Venus
Explanation: Scroll right and enjoy this 180 degree panorama across the South African Astronomical Observatory's hilltop Sutherland observing station. Featured are SAAO telescope domes and buildings, along with the dark, wedge-shaped shadow of planet Earth stretching into the distance, bounded above by the delicately colored antitwilight arch. Visible along the antisunward horizon at sunset, (or sunrise) the pinkish antitwilight arch is also known as the Belt of Venus. In order, the significant structures from left to right house; the giant SALT 11-meter instrument, the internet telescope MONET, the 1.9 meter Radcliffe, the 1.0 meter Elizabeth, a 0.75 meter reflector, a 0.5 meter reflector, a garage, YSTAR, BiSON, ACT, IRSF (open), and a storage building. (Note to SAAO fans: in this east-facing view the planet-hunter SuperWASP south is hidden behind the IRSF.)

APOD: 2006 April 30 - 1006 AD: Supernova in the Sky
Explanation: A new star, likely the brightest supernova in recorded human history, appeared in planet Earth's sky about 1,000 years ago today, in 1006 AD. The expanding debris cloud from the stellar explosion is still visible to modern astronomers, but what did the supernova look like in 1006? In celebration of the millennial anniversary of SN1006, astronomer Tunc Tezel offers this intriguing suggestion, based on a photograph he took on February 22, 1998 from a site overlooking the Mediterranean south of Antalya, Turkey. On that date, bright Venus and a waning crescent Moon shone in the early morning sky. Adopting calculations which put the supernova's apparent brightness between Venus and the crescent Moon, he digitally superposed an appropriate new star in the picture. He placed the star at the supernova's position in the southerly constellation of Lupus and used the water's reflection of moonlight in the final image.

APOD: 2006 March 3 - Venus and Comet Pojmanski
Explanation: Shining brightly in the east at dawn, Venus dominates the sky in this view over a suburban landscape from Bursa, Turkey. An otherwise familiar scene for astronomer Tunc Tezel, his composite picture of the morning sky recorded on March 2nd also includes a surprise visitor to the inner solar system, Comet Pojmanski. Cataloged as C/2006 A1, the comet was discovered on January 2nd by Grzegorz Pojmanski of Warsaw University Astronomical Observatory in Poland. At the time very faint and tracking through southern skies, the comet has now moved north and grown just bright enough to be a good target for early-rising skygazers with binoculars. Enhanced and framed in this picture, the comet's tail has also grown to a length of several degrees. The comet will be at its closest approach to planet Earth, just over 100 million kilometers away, on March 5. For northern hemisphere observers in the next few days, the beginning of morning twilight really will be the best time to spot Comet Pojmanski.

APOD: 2006 February 4 - Shadow Set
Explanation: A nearly full Moon and planet Earth's shadow set together in this scene captured on January 13th from snowy Mt. Jelm, home of the Wyoming Infrared Observatory. For early morning risers (and late to bed astronomers), shadow set in the western sky is a daily apparition whose subtle beauty is often overlooked in favor of the more colorful eastern horizon. Extending through the dense atmosphere, Earth's setting shadow is seen in this picture as a dark blue band along the distant horizon, bounded above by a pinkish glow or antitwilight arch. Known as the Belt of Venus, the arch's lovely color is due to backscattering of reddened light from the rising Sun. The setting Moon's light is also reddened by the long sight-line through the atmosphere.

APOD: 2006 February 1 - Venus Just After Sunset
Explanation: Is that Venus or an airplane? A common ponderable for sky enthusiasts is deciding if that bright spot near the horizon is the planet Venus. Usually, an airplane will show itself by moving significantly in a few moments. Venus will set only slowly as the Earth turns. Still, the identification would be easier if Venus did not keep shifting its position each night. Pictured above, Venus was captured 38 different nights during 2005 and 2006 over Bursa, Turkey, when Earth's sister planet appeared exclusively in the evening sky. The average spacing of the images was about five days, while the images were always taken with the Sun about 7 degrees below the horizon. Venus' orbit around the Sun will now confine it to Earth's morning sky until October 2006.

APOD: 2006 January 10 - The Phases of Venus
Explanation: Venus goes through phases. Just like our Moon, Venus can appear as full as a disk or as a thin as a crescent. Venus, frequently the brightest object in the post-sunset or pre-sunrise sky, appears so small, however, that it usually requires binoculars or a small telescope to clearly see its current phase. The above time-lapse sequence, however, was taken over the course of many months and shows not only how Venus changes phase but how it's apparent angular size also changes. In the middle negative image, Venus is in a new phase, the same phase that occurred during its rare partial eclipse of the Sun in 2004.

APOD: 2006 January 4 - Hauoli Makahiki Hou
Explanation: Fading sunlight, a young crescent Moon, and brilliant Venus shared the western sky in this view of 2005's final sunset from the top of Mount Haleakala, on Maui, Hawaii. Also known as the Sacred House of the Sun, Haleakala, is Maui's dormant volcano. At 10,000 feet the summit is an ideal site for astronomical observatories, and this scene also features the silhouette of the northern hemisphere Faulkes Telescope. Of particular interest to students the Faulkes Telescope is a 2-meter diameter instrument, dedicated to astronomy education, that can be remotely operated over the internet. The project is a joint effort between the Dill Faulkes Educational Trust and the University of Hawaii Institute for Astronomy. Of course on Haleakala, "Happy New Year" would be "Hauoli Makahiki hou" (how-oh-lee ma-ka-hee-key ho).

APOD: 2005 December 9 - December Moon Meets Evening Star
Explanation: If you've been outdoors near sunset, then you've probably noticed Venus low in the west as the brilliant evening star. Sometimes mistaken for a tower light near the horizon, Venus is the third brightest celestial beacon, after the Sun and Moon, in planet Earth's sky. That distinction is particularly easy to appreciate in this peaceful scene featuring the crescent Moon, Venus, and sunset colors captured on December 4th near Albany, Missouri, USA. As this season's evening star, Venus will be at its most brilliant tonight, but as December progresses the bright planet will begin to fall out of the western sky. By early next week, December's Moon will have moved on to meet another bright planet overhead -- Mars.

APOD: 2005 October 31 - A Martian Halloween
Explanation: From sunset to sunrise, an unusually bright yellowish orb will hang in the sky this Halloween: Mars. Yesterday, Earth passed Mars as they orbited the Sun, bringing Mars closer than it will be for the next thirteen years. Tonight though, Mars will be nearly as bright as last night, a beacon of extraterrestrial spookiness. Opposite the Sun, Mars will rise just when the Sun sets, set just when the Sun rises, and be visible the entire night. Mars will not always be the brightest object in tonight's sky, though. Brighter than even Mars, almost spooky Venus will light up the western horizon for a brief time just after sunset. Please have a safe and happy All Hallows Eve.

APOD: 2005 October 30 - A Dark and Stormy Night
Explanation: It was a dark and stormy night. But on 2003 August 29th the red planet Mars, near its closest approach to Earth in almost 60,000 years, shone brightly in the sky against a background of stars in the constellation Aquarius. In the foreground of this scary view, huge thunder clouds are lit by lightning strokes from within. Mars, of course, has nothing to do with storms on Earth, though both have the power to excite the imagination and wonder of Earthdwellers. Tonight, the night before Halloween, Mars will also pass close to the Earth, closer than it will come during the next thirteen years. And once again, the red planet Mars will look particularly bright, although much smaller and dimmer than the Moon and even Venus.

APOD: 2005 October 19 - On the Possibility of Ascending to Mars
Explanation: On another October 19, in 1899, a 17 year-old Robert Goddard climbed a cherry tree on a beautiful autumn afternoon in Worcester, Massachusetts. Inspired by H.G. Wells' War of the Worlds and gazing out across a meadow, young Goddard imagined it would be wonderful to make a device that had the possibility of ascending to Mars. Forever more he felt his life had a purpose and in the following years his diary entries record October 19th as "Anniversary Day", the anniversary of his ascent into the cherry tree. By 1926 he had designed, built, and flown the world's first liquid fuel rocket. Mars is just visible through the trees at the lower right in this dramatic sky view that also features the Moon and Venus -- all visited by liquid fuel rockets constructed on principles developed by Goddard.

APOD: 2005 September 28 - A Rocket Launch at Sunset
Explanation: What kind of cloud is that? Last week, a sunset rocket launch lit up the sky and was photographed by sky enthusiasts as far as hundreds of miles away. The lingering result was a photogenic rocket plume. Not everyone who saw the resulting plume knew its cause to be a Minotaur rocket launched from Vandenberg Air Force Base in California, USA. The cloud was visible after sunset on 22 September. Fuel particles and water droplets expelled from the rocket swirled in the winds of the upper atmosphere, creating an expanding helix. The noctilucent plume was so high that it still reflected sunlight, where lower clouds in the foreground appeared dark. The above image also captured part of the plume reflecting sunlight as a rainbow or a colorful iridescent cloud. Below the launch plume is the planet Venus.

APOD: 2005 September 13 - A Quadruple Sky Over Great Salt Lake
Explanation: This was a sky to show the kids. All in all, three children, three planets, the Moon, a star, an airplane and a mom were all captured in one image near Great Salt Lake in Utah, USA on September 6. Minus the airplane and the quadruple on the ground, this busy quadruple coincidence sky was visible last week all over the world. The easiest object to spot is the crescent Moon, which is easily the brightest sky orb in the above image. Venus is the highest planet in the sky, with Jupiter to its right. The bright star Spica completes the quadruple just below Venus. The streak on the far right is an airplane. Mom is seated. Grandpa, appreciating the beauty of the moment, took the picture.

APOD: 2005 September 9 - Moon River
Explanation: Shortly after sunset on September 6th, sky gazers around the world were treated to a lovely crescent Moon in western skies -- joined by bright planets Venus and Jupiter. In this colorful telephoto view from near Quebec City, Canada the Moon is nestled just above the wide St. Lawrence River. Lights on the horizon are along the river's southern shore. Also known as the evening star, Venus is at the upper left and Jupiter at the upper right, while another prominent celestial beacon, Spica, can be seen shining through the twilight below Venus. Spica, actually a very close pair of hot blue stars some 260 light-years away, is the brightest star in the constellation Virgo.

APOD: 2005 September 3 - Venus Unveiled
Explanation: The surface of Venus is perpetually covered by a veil of thick clouds and remains hidden from even the powerful telescopic eyes of earth-bound astronomers. But in the early 1990s, using imaging radar, the Venus orbiting Magellan spacecraft was able to lift the veil from the face of Venus and produced spectacular high resolution images of the planet's surface. Colors used in this computer generated picture of Magellan radar data are based on color images from the surface of Venus transmitted by the Soviet Venera 13 and 14 landers. The bright area running roughly across the middle represents the largest highland region of Venus known as Aphrodite Terra.

APOD: 2005 August 17 - Planets over Paranal
Explanation: Very bright planets and very large telescopes are part of this sunset view of Paranal Observatory. The observatory's four, massive 8.2 meter telescope units are situated on top of the 2,600 meter high mountain, Cerro Paranal, in the dry Atacama Desert in northern Chile. The individual unit telescopes can be used separately or in combination and are named Antu, Kueyen, Melipal, and Yepun. Together they are fittingly known as the European Southern Observatory's Very Large Telescope. Of course, the very bright planets are Venus (near center), joined by Mercury (below) and Saturn (left) in late June's western evening skies.

APOD: 2005 August 9 - The Belt of Venus over Elwood Beach
Explanation: Although you've surely seen it, you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly off-color, slightly pink. Called the Belt of Venus, this off-color band between the dark eclipsed sky and the blue sky can be seen in nearly every direction including that opposite the Sun. Straight above, blue sky is normal sunlight reflecting off the atmosphere. In the Belt of Venus, however, the atmosphere reflects light from the setting (or rising) Sun which appears more red. The Belt of Venus can be seen from any location with a clear horizon. Pictured above, the Belt of Venus was photographed behind Elwood Beach in Melbourne, Australia. The belt is frequently caught by accident in other photographs.

APOD: 2005 July 15 - Reflections on the Inner Solar System
Explanation: Only Mars is missing from this reflective view of the major rocky bodies of the inner solar system. Captured on July 8th, the serene, twilight picture looks out over the Flat Tops Wilderness area from near Toponas, Colorado, USA and includes planets Mercury, Venus, Earth, and Earth's large natural satellite, the Moon. The Moon is in a young crescent phase about three degrees above bright planet Venus. Forest fires contribute to a layer of smoke in Earth's sky that almost hides planet Mercury, still visible very near the horizon. Just a week earlier Venus and Mercury were joined by Saturn, forming a notable grouping in the west also enjoyed by skygazers across planet Earth.

APOD: 2005 July 2 - Three Planets by the Sea
Explanation: On Tuesday, June 28th, the setting Sun flooded the horizon with a beautiful warm light in this view from the beach beside the pier at Brighton in Adelaide, South Australia. The Sun also illuminated three planets gathered in the western sky, Mercury, Venus, and Saturn. From this perspective Mercury is at the highest point in the celestial triangle, brilliant Venus is just below, and Saturn stands farther to the left and below the close pair. Of course, the planets only appear close together on the sky but are actually quite far apart in space. The orbits of Mercury and Venus are both interior to Earth's orbit, while gas giant Saturn lies in the outer solar system, over nine astronomical units from the Sun. Late next week, Venus and Mercury will share western skies with the young crescent Moon.

APOD: 2005 June 30 - Three Planets from Mt Hamilton
Explanation: Venus, Mercury, and Saturn wandered close together in western evening skies last week. On Saturnday, June 25, astronomer R. Jay GaBany recorded this snapshot of their eye-catching planetary conjunction, from historic Lick Observatory on Mt. Hamilton, California, USA. The view looks toward the Pacific shortly after sunset with the lights of San Jose and the southern San Francisco Bay area in the foreground. Of course, Venus is the brightest of the trio. Mercury is nearby on the right and Saturn is below and left, closest to the horizon. Farther to the right of the planetary triangle are Pollux and Castor, twin stars of Gemini, with Regulus, bright star of the constellation Leo, at the very upper left corner of the picture. In the coming days, Venus and Mercury remain close, while Saturn continues to drop below them, toward the horizon.

APOD: 2005 June 25 - Venus: Just Passing By
Explanation: Venus, the second closest planet to the Sun, is by far the brightest of the three planets gathered in this weekend's western sky at sunset. It has also proven to be a popular way-point for spacecraft headed for the gas giant planets in the outer reaches of the solar system. Why visit Venus first? Using a gravity assist maneuver, spacecraft can swing by planets and gain energy during their brief encounter, saving fuel for use at the end of their long interplanetary voyage. This colorized image of Venus was recorded by the Jupiter-bound Galileo spacecraft shortly after its gravity assist flyby of Venus in February of 1990. Galileo's glimpse of the veiled planet shows structure in swirling sulfuric acid clouds. The bright area is sunlight glinting off the upper cloud deck.

APOD: 2005 June 24 - Planets in the West
Explanation: This weekend three planets will grace the western sky, forming a lovely trio easily visible shortly after sunset. Saturday evening in particular will find Saturn, Venus, and Mercury all within a 2 degree circle (about the size of your thumb held at arm's length) above the western horizon. Recorded last Sunday, June 19, this image shows the same three planets arrayed along the ecliptic plane above a Colorado Rocky Mountain skyline. Venus is easiest to pick out of the twilight, the brightest celestial beacon below picture center, with Saturn above and to the left of Venus, and Mercury closest to the horizon, right of prominent Pinnacle Peak. By Saturday, the wandering planets will draw even closer together. For help spotting the planets here, put your cursor over the picture.

APOD: 2005 June 9 - Venus Returns to the Evening Sky
Explanation: This serene image of boats moored in the harbor of l'Île-Tudy, Bretagne, France was taken on June 1st, about an hour after sunset. It also features Venus, third brightest celestial object after the Sun and Moon. For casual skygazers, this month marks Venus' return to the evening sky as the brilliant 'star', shining low in the west-northwest shortly after sunset. In the picture, astrophotographer and APOD translator Laurent Laveder notes that Venus is easily mistaken for a light atop a sailboat's tall mast, giving the otherwise stunning celestial beacon an unremarkable appearance. Of course, a year ago Venus' appearance was quite remarkable. On June 8, 2004, Venus crossed the Sun's disk, the first transit of Venus since 1882. Late this week Venus shares the evening sky with the young crescent Moon, and will next transit the Sun on June 6, 2012.

APOD: 2005 May 3 - Solar System Rising Over Fire Island
Explanation: If you wait long enough, the entire Solar System will rise before you. To see such a sight, however, you will need to look in the direction of the ecliptic. All of the planets and their moons orbit the Sun in nearly the same plane, the ecliptic plane. From the Earth, this means that each day they will all rise in nearly the same direction - and later set in the opposite direction. Ten years ago, a series of time exposures caught, left to right, the Sun, Venus, the Moon, and Jupiter, all rising in the ecliptic plane behind Fire Island, New York, USA. Exposures were taken every six minutes and digitally superposed on an image taken from the same location at sunrise. Smaller members of our Solar System, including most comets and many asteroids, do not always move along the ecliptic plane. The picturesque Fire Island Lighthouse, visible in the foreground, was built in 1826 and is still in use today.

APOD: 2005 April 10 - Venus' Once Molten Surface
Explanation: If you could look at Venus with radar eyes - this is what you might see. This computer reconstruction of the surface of Venus was created from data from the Magellan spacecraft. Magellan orbited Venus and used radar to map our neighboring planet's surface between 1990 and 1994. Magellan found many interesting surface features, including the large circular domes, typically 25-kilometers across, that are depicted above. Volcanism is thought to have created the domes, although the precise mechanism remains unknown. Venus' surface is so hot and hostile that no surface probe has lasted more than a few minutes.

APOD: 2005 January 27 - Shadow Set
Explanation: A nearly full Moon and planet Earth's shadow set together in this scene captured Monday from snowy Mt. Jelm, home of the Wyoming Infrared Observatory. For early morning risers (and late to bed astronomers), shadow set in the western sky is a daily apparition whose subtle beauty is often overlooked in favor of the more colorful eastern horizon. Extending through the dense atmosphere, Earth's setting shadow is seen in this picture as a dark blue band along the distant horizon, bounded above by a pinkish glow or antitwilight arch. Also known as the Belt of Venus, the arch's lovely color is due to backscattering of reddened light from the rising Sun. The setting Moon's light is also reddened by the long sight-line through the atmosphere and echoes the dawn sky's yellow-orange hues.

APOD: 2005 January 7 - S is for Venus
Explanation: Planet Venus traced out this S shape in Earth's sky during 2004. Following the second planet from the Sun in a series of 29 images recorded from April 3rd through August 7th (top right to bottom left) of that year, astronomer Tunc Tezel constructed this composite illustrating the wandering planet's path against the background stars. The series reveals Venus' apparent retrograde motion transporting it from a brilliant evening star to morning's celestial beacon. Of course, in 2004, after sinking into the evening twilight but before rising above the predawn horizon, Venus was seen in silhouette against the Sun (near center) - the first transit of Venus since 1882. The next time Venus will wander across the solar disk is in 2012.

APOD: 2004 November 13 - Moon Over Shiraz
Explanation: Early morning risers around the world have enjoyed the sight of bright planets in this week's predawn skies - further enhanced by the celestial spectacle of the waning crescent Moon. From some locations the Moon was seen to pass in front of Jupiter or Venus, a lunar occultation. Recorded near sunrise on November 10th from Shiraz, Iran, this eastern horizon view finds Jupiter (top) and a brilliant Venus in line with the Moon, a lovely conjunction of the three brightest objects in the night sky. Although the Moon has now fallen out of the early morning scene, Venus and Jupiter (along with a much fainter Mars) still precede the rising Sun above the eastern horizon.

APOD: 2004 November 8 - Jupiter and Venus at Sunrise
Explanation: What are those bright objects in the morning sky? Early morning dog walkers, among many others across our world's Northern Hemisphere, have likely noticed tremendously bright Venus hanging in the eastern sky just before sunrise. Looking a bit like an approaching airplane, Venus holds its place in the sky and never seems to land. Last week, impressive but less bright Jupiter appeared within a degree of the Venusian orb, creating a dazzling sky that you might appreciate a bit more than your dog. This night sky early show will change slightly over the next week, with the planets moving past each other, Mars moving into the picture, guest stars like Spica appearing to shift in the background, and even a crescent Moon stopping in for a cameo. Pictured above last week, Jupiter and Venus were photographed rising before the Sun over the city of Bursa, Turkey.

APOD: 2004 August 14 - Messenger Launch
Explanation: Streaking into the early morning sky on August 3rd, a Delta II rocket launches NASA's Messenger spacecraft on an interplanetary voyage to Mercury. Scheduled to become the first probe to orbit Mercury, Messenger will begin by looping through the inner Solar System in a series of close flybys of planet Earth and Venus. The flybys are designed as trajectory changing gravity assist encounters to ultimately achieve the goal of orbiting Mercury in 2011. Prior to entering orbit, Messenger will also flyby Mercury in 2008 and 2009 as the first spacecraft to visit the Solar System's innermost planet since Mariner 10 in the mid 1970s. This dramatic view of the Messenger launch was recorded from a pier in Jetty Park at the north end of Cocoa Beach about 2.5 miles from the Cape Canaveral launch site. So what's that erratic blue streak on the right? It's the reflection from a camera blurred in the time exposure.

APOD: 2004 July 26 - A Large Active Region Crosses the Sun
Explanation: An unexpectedly large sunspot region is now crossing the Sun. The active region is home to rivers of hot plasma, explosive flares, strong magnetic fields, a powerful Coronal Mass Ejection (CME), and a sunspot group so large it can be seen by the protected eye without magnification. In fact, this region appears larger than Venus did when it crossed the Sun last month. Pictured above is a close-up of this sunspot group, officially tagged AR 10652, taken just four days ago. The region is now nearing the Sun's eastern limb and will disappear from view in a few days. Energetic ions from sunspot group 652 continue to impact the Earth and create rare purple auroras.

APOD: 2004 July 20 - Space Station, Venus, Sun
Explanation: On June 8, Venus was not the only celestial object to pass in front of the Sun. A few well-situated photographers caught the International Space Station also crossing the Sun simultaneously. Pictured above is a unique time-lapse image of the unprecedented double transit, a rare event that was visible for less than a second from a narrow band on Earth. The above image is a combination of 12 frames taken 0.033 seconds apart and each themselves lasting only 1/10,000 th of a second. The image was taken from the small village of Stupava in Slovakia. The next time Venus will appear to cross the Sun from Earth will be in 2012.

APOD: 2004 July 17 - Transit of Venus Stereogram
Explanation: Venus glides in front of an enormous solar disk in these two frames from the TRACE satellite imaging of the inner planet's 2004 transit. Arranged in a "right/left" stereogram, the frames are intended to be viewed at a comfortable distance from the screen with your eyes gently crossed, allowing the images to merge and produce a pleasing stereo effect. Shown during the ingress (beginning) phase of the transit, the silhouetted portion of the planet appears to float dramatically in front of the Sun's granulated surface. Of course, the dense Cytherian (Venusian) atmosphere also scatters and refracts the intense sunlight. The effect is visible across the portion of the planet still beyond the Sun's edge and viewed against the blackness of space.

APOD: 2004 July 3 - Cassini to Venus
Explanation: Saturn Orbiter Cassini with Titan Probe Huygens attached rocketed into early morning skies on October 15, 1997. The mighty Titan 4B Centaur rocket is seen here across the water, arcing away from Launch Complex 40 at Cape Canaveral Air Station. Cassini, a sophisticated robot spacecraft was actually headed toward inner planet Venus, the first way point in its 7 year, 2.2 billion mile interplanetary journey to Saturn. In fact, Cassini swung by Venus during April 1998 and June 1999, Earth in August 1999, and Jupiter in December 2000. During each of these "gravity assist" encounters the six ton spacecraft picked up speed, reaching Saturn only three days ago. Cassini is now orbiting the ringed gas giant, with the Huygens Probe scheduled to separate from the spacecraft in December. The probe's descent to the surface of Saturn's large moon Titan will be the most distant landing ever attempted.

APOD: 2004 June 27 - Galaxy Cluster Abell 1689 Warps Space
Explanation: Two billion light-years away, galaxy cluster Abell 1689 is one of the most massive objects in the Universe. In this view from the Hubble Space Telescope's Advanced Camera for Surveys, Abell 1689 is seen to warp space as predicted by Einstein's theory of gravity -- bending light from individual galaxies which lie behind the cluster to produce multiple, curved images. The power of this enormous gravitational lens depends on its mass, but the visible matter, in the form of the cluster's yellowish galaxies, only accounts for about one percent of the mass needed to make the observed bluish arcing images of background galaxies. In fact, most of the gravitational mass required to warp space enough to explain this cosmic scale lensing is in the form of still mysterious dark matter. As the dominant source of the cluster's gravity, the dark matter's unseen presence is mapped out by the lensed arcs and distorted background galaxy images.

APOD: 2004 June 23 - A Picturesque Venus Transit
Explanation: The rare transit of Venus across the face of the Sun earlier this month was one of the better-photographed events in sky history. Both scientific and artistic images have been flooding in from the areas that could see the transit: Europe and much of Asia, Africa, and North America. Scientifically, solar photographers confirmed that the black drop effect is really better related to the viewing clarity of the camera or telescope than the atmosphere of Venus. Artistically, images might be divided into several categories. One type captures the transit in front of a highly detailed Sun. Another category captures a double coincidence such as both Venus and an airplane simultaneously silhouetted, or Venus and the International Space Station in low Earth orbit. A third image type involves a fortuitous arrangement of interesting looking clouds, as shown by example in the above image taken from North Carolina, USA. There the distant orb of giant Venus might have been mistaken, at first glance, for a small but unusually circular cloud.

APOD: 2004 June 15 - A Rare Annular Venusian Solar Eclipse
Explanation: An unusual type of solar eclipse occurred last week. Usually it is the Earth's Moon that eclipses the Sun. Last week, for the first time in over 100 years, the planet Venus took a turn. Like a solar eclipse by the Moon, the phase of Venus became a continually thinner crescent as Venus became increasingly better aligned with the Sun. Eventually the alignment became perfect and the phase of Venus dropped to zero. The dark spot of Venus crossed our parent star. The situation could technically be labeled a Venusian annular eclipse with an extraordinarily large ring of fire. From above the thick cloud tops of Venus, the Earth appeared in its fullest phase, brighter in the Venusian sky than even Mars appeared from Earth last August. Hours later, as Venus continued in its orbit, a slight crescent phase appeared again. The next Venusian solar eclipse will occur in 2012.

APOD: 2004 June 11 - Venus and the Chromosphere
Explanation: Enjoying the 2004 Transit of Venus from Stuttgart, Germany, astronomer Stefan Seip recorded this fascinating, detailed image of the Sun. Revealing a network of cells and dark filaments against a bright solar disk with spicules and prominences along the Sun's limb, his telescopic picture was taken through an H-alpha filter. The filter narrowly transmits only the red light from hydrogen atoms and emphasizes the solar chromosphere -- the region of the Sun's atmosphere immediately above its photosphere or normally visible surface. Here, the dark disk of Venus seems to be imitating a giant sunspot that looks perhaps a little too round. But in H-alpha pictures like this one, sunspot regions are usually dominated by bright splotches (called plages) on the solar chromosphere.

APOD: 2004 June 10 - Venus at the Edge
Explanation: With Venus in transit at the Sun's edge on June 8th, astronomers captured this tantalizing close-up view of the bright solar surface and partially silhouetted disk. Enhanced in the sharp picture, a delicate arc of sunlight refracted through the Venusian atmosphere is also visible outlining the planet's edge against the blackness of space. The arc is part of a luminous ring or atmospheric aureole, first noted and offered as evidence that Venus did posses an atmosphere following observations of the planet's 1761 transit. The image was recorded using the 1-meter Swedish Solar Telescope located on La Palma in the Canary Islands. For the Institute for Solar Physics, Dan Kiselman, Goran Scharmer, Kai Langhans, and Peter Dettori were at the telescope, while Mats Lofdahl produced the final image. Excellent movies of the transit - including one of the emergence of Venus' atmospheric aureole - are available from the Dutch Open Telescope, also observing from La Palma.

APOD: 2004 June 9 - Venus Transit at Sunrise
Explanation: Did you see the transit? While some watched by webcast, sky gazers in Europe, the Middle East, Africa, and Asia were able to witness the complete 6 hour journey of Venus' silhouetted disk across the face of the Sun. As seen from North America, the much heralded Venus Transit of 2004 was nearing its final stages at sunrise yesterday in this telescopic image. The view looks across the Atlantic from Tybee Island near Savannah, Georgia, USA. In fact, many in eastern North America experienced a dramatic view of a perfect, dark, round Venus against a reddened Sun filtered by banks of low clouds. Ironically, the Sun takes on the appearance of a cloud covered planet itself as Venus marches toward the right through this dreamlike scene.

APOD: 2004 June 8 - A Planet Transits the Sun
Explanation: Today an astronomical event will occur that no living person has ever seen: Venus will cross directly in front of the Sun. A Venus crossing, called a transit, last occurred in 1882 and was front-page news around the world. Today's transit will be visible in its entirety throughout Europe and most of Asia and Africa. The northeastern half of North America will see the Sun rise with the dark dot of Venus already superposed. Never look directly at the Sun, even when Venus is in front. Mercury's closer proximity to the Sun cause it to transit every few years. In fact, the above image mosaic of Mercury crossing the Sun is from two transits ago, in November 1999. Will anyone living see the next Venus transit? Surely yes since it occurs in 2012.

APOD: 2004 June 7 - Mammatus Clouds Over Mexico
Explanation: When do cloud bottoms appear like bubbles? Normal cloud bottoms are flat because moist warm air that rises and cools will condense into water droplets at a very specific temperature, which usually corresponds to a very specific height. After water droplets form that air becomes an opaque cloud. Under some conditions, however, cloud pockets can develop that contain large droplets of water or ice that fall into clear air as they evaporate. Such pockets may occur in turbulent air near a thunderstorm, being seen near the top of an anvil cloud, for example. Resulting mammatus clouds can appear especially dramatic if sunlit from the side. The above mammatus clouds were photographed last month over Monclova, Mexico.

APOD: 2004 June 6 - Mercury Spotting
Explanation: Can you spot the planet? The diminutive disk of Mercury, the solar system's innermost planet, spent about five hours crossing in front of the enormous solar disk on 2003 May 7, as viewed from the general vicinity of planet Earth. The Sun was above the horizon during the entire transit for observers in Europe, Africa, Asia, or Australia, and the horizon was certainly no problem for the sun-staring SOHO spacecraft. Seen as a dark spot, Mercury progresses from left to right (top panel to bottom) in these four images from SOHO's extreme ultraviolet camera. The panels' false-colors correspond to different wavelengths in the extreme ultraviolet which highlight regions above the Sun's visible surface. This was the first of 14 transits of Mercury which will occur during the 21st century, but the next similar event will be a much more rare transit of Venus this coming Tuesday. Need help spotting Mercury? Just click on the picture.

APOD: 2004 June 4 - Sedna at Noon
Explanation: Standing on Sedna - the solar system's most distant known planetoid - your view of the Sun at high noon might look something like this. An artist's dramatic vision, the picture shows the Sun suspended above the nearby horizon as a bright star immersed in the dusty ecliptic plane. Within the dust-scattered sunlight are more familiar members of the solar system, including planet Earth. But at a distance of about 13 billion kilometers (8 billion miles) Earth would only be visible in binoculars or a small telescope. In Sedna's dark, daytime skies, the noonday Sun is also joined by the faint stars and obscuring dust clouds of the Milky Way, suspended on the left above stark, ruddy terrain. For Sedna-based sky gazers, all planets have interior orbits and would remain close to the Sun in Sedna's skies. Of course, for earthbound astronomers, interior planets Venus and Mercury also remain near the Sun, with Venus scheduled for a rare crossing of the solar disc on June 8.

APOD: 2004 May 24 - Planets Over Easter Island
Explanation: It isn't every day that planets line up behind a stone giant. For one thing, it helps to have a good planet line-up, such as occurred in the sky just last month. For another, it helps to be on Easter Island, where over 800 large stone statues exist. The Easter Island statues, stand, on the average, over twice as tall as a person and have over 200 times as much mass. Few specifics are known about the history or meaning of the unusual statues, but many believe that they were created about 500 years ago in the images of local leaders of a lost civilization. Pictured above, the Moon, Venus, and Mars can be seen behind Ahu Tahai, a famous Easter Island statue. The bright star Aldebaran is also visible.

APOD: 2004 May 21 - Phases of Venus
Explanation: Venus is currently falling out of the western evening sky. Second planet from the Sun and third brightest celestial object after the Sun and Moon, Venus has been appreciated by casual sky gazers as a brilliant beacon above the horizon after sunset. But telescopic images have also revealed its dramatic phases. In fact, this thoughtful composite of telescopic views nicely illustrates the progression of phases and increase in apparent size undergone by Venus over the past few weeks. Gliding along its interior orbit, Venus has been catching up with planet Earth, growing larger as it draws near. At the same time, just as the Moon goes through phases, Venus' visible sunlit hemisphere has presented an increasingly slender, crescent shape. Now sharing the sky with a crescent Moon, on June 8th Venus will actually cross the face of the Sun, the first such transit since 1882.

APOD: 2004 May 16 - Venus: Earth's Cloudy Twin
Explanation: This picture by the Galileo spacecraft shows just how cloudy Venus is. Venus is very similar to Earth in size and mass - and so is sometimes referred to as Earth's sister planet - but Venus has a quite different climate. Venus' thick clouds and closeness to the Sun (only Mercury is closer) make it the hottest planet - much hotter than the Earth. Humans could not survive there, and no life of any sort has ever been found. When Venus is visible it is usually the brightest object in the sky after the Sun and the Moon. More than 20 spacecraft have visited Venus including Venera 9, which landed on the surface, and Magellan, which used radar to peer through the clouds and make a map of the surface. This visible light picture of Venus was taken by the Galileo spacecraft that orbited Jupiter from 1995 to 2003. Many things about Venus remain unknown, including the cause of mysterious bursts of radio waves.

APOD: 2004 May 1 - A Western Sky at Twilight
Explanation: On April 23rd, the Moon along with planets Saturn, Mars, and Venus (and planet Earth of course ...) were all visible in the west at twilight, captured here from a site near Saylorvillle Lake north of Des Moines, Iowa, USA. Putting your cursor over the image will label our fellow solar system wanderers and also reveal the approximate trajectory of the ecliptic plane - defined by Earth's orbit around the Sun - angling above the western horizon. After sunset tonight, the western sky will present a similar arrangement of planets, although the Moon will have moved east out of the picture, passing bright Jupiter along the ecliptic and heading for May 4th's total lunar eclipse. May could also be a good month for comets.

APOD: 2004 April 29 - Titan's X-Ray
Explanation: This June's rare and much heralded transit of Venus will feature our currently brilliant evening star in silhouette, as the inner planet glides across the face of the Sun. But on January 5, 2003 an even rarer transit took place. Titan, large moon of ringed gas giant Saturn, crossed in front of the Crab Nebula, a supernova remnant some 7,000 light-years away. During Titan's transit, the orbiting Chandra Observatory's x-ray detectors recorded the shadowing of cosmic x-rays generated by the Crab's amazing pulsar nebula, pictured above, in a situation analogous to a medical x-ray. The resulting image (inset at left) probes the extent of Titan's atmosphere. So, how rare was Titan's transit of the Crab? While Saturn itself passes within a few degrees of the Crab Nebula every 30 years, the next similar transit is reportedly due in 2267. And since the stellar explosion which gave birth to the Crab was seen in 1054, the 2003 Titan transit may have been the first to occur ... ever.

APOD: 2004 April 15 - Venus and the Pleiades
Explanation: Venus still rules the western skies after sunset as the brilliant evening star. While wandering the ecliptic with its fellow naked-eye planets earlier this month, it passed near the Pleiades star cluster, providing a striking photo opportunity for earthbound skygazers. Cataloged as M45, the Pleiades stars make for a lovely sight on their own, often shown in long exposure images immersed in hazy blue reflection nebulae. In this picture though, recorded on the evening of April 3rd, brilliant Venus closes with the Seven Sisters and overwhelms the light from the delicate cosmic clouds. The view offers a study in contrasts as Venus appears about 700 times brighter than Alcyone, the Pleiades brightest star. With Venus just over 5 light-minutes from Earth, Alcyone and the other Pleiades cluster stars are about 400 light-years distant. Formed out of the contracting nebula which gave birth to the Sun, Venus is also roughly 4.5 billion years old. The stars of the Pleiades are likely aged a mere hundred million years.

APOD: 2004 April 2 - Mercury and Venus in the West
Explanation: Doing their part in the ongoing dance of the planets, Mercury and Venus both reached their greatest elongation or maximum apparent distance from the Sun only a few days ago, on March 29th. Eager to record their celestial accomplishment, astronomer Jimmy Westlake snapped this view of the two inner most planets shining in western twilight skies above Yampa, Colorado, USA. The picture was taken using a digital camera mounted on a tripod. Mercury is easily the brightest celestial object near the horizon, appearing to the right of the foreground structure and just above a thin cloud silhouetted by fading sunlight. Still, near the top of the picture brilliant Venus dominates the scene as the magnificent evening star. After climbing in western skies throughout the month of March, Venus lies just below the Pleiades star cluster. Tonight and tomorrow night, skygazers can spot Venus at the southern edge of the Pleiades.

APOD: 2004 March 26 - Moon and Planets Sky
Explanation: Look up into the sky tonight and without a telescope or binoculars you might have a view like this one of Moon, planets and stars. The lovely photo was taken on March 23rd, and captures the crescent Moon on the horizon with Venus above it. Both brilliant celestial bodies are over-exposed. Farther above Venus is the tinted glow of Mars with the Pleiades star cluster just to the red planet's right. The V-shaped arrangement of stars to the left of Mars is the Hydaes star cluster. Bright red giant Aldebaran, not itself a member of the Hyades cluster, marks the top left of the V. During the next week, all five naked-eye planets, Mercury, Venus, Mars, Jupiter, and Saturn, along with the Moon will grace the evening sky together - a lunar and planetary spectacle that can be enjoyed by skygazers around the world. But look just after sunset, low on the western horizon, to see Mercury before it sets. The next similar gathering of the planets will be in 2008.

APOD: 2004 March 23 - Lava Flows on Venus
Explanation: The hot surface of Venus shows clear signs of ancient lava flows. Evidence of this was bolstered by the robot spacecraft Magellan, which orbited Venus in the early 1990s. Using imaging radar, Magellan was able to peer beneath the thick perpetual clouds that cover Earth's closest planetary neighbor. Picture above, lava apparently flowed down from the top of the image and pooled in the light colored areas visible across the image middle and bottom. The lava cut a channel across the darker ridge that runs horizontally across the image center. The picture covers about 500 kilometers across. The lava originates from a caldera named Ammavaru that lies about 300 kilometers off the image top. The hot dense climate makes Venus a more difficult planet on which to land spacecraft and rovers. Venus currently sparkles as the brightest object in the western sky after sunset.

APOD: 2004 March 8 - Moon and Venus over Corona Del Mar Beach
Explanation: The crescent Moon passed nearly in front of Venus two weeks ago. The close conjunction of the night sky's two brightest objects created a striking pose for many viewing the evening sky just after sunset. Such a pose, shown above, was captured between clouds over Corona Del Mar Beach in California, USA. To be precise, the Moon appeared to pass only about three degrees from Venus on February 23. A similar conjunction will occur later this month, on March 24, when Venus appears near its furthest from the Sun while the Moon passes only about 2 degrees away.

APOD: 2004 March 1 - Cassini Closes in on Saturn
Explanation: Are they gone? They were not originally predicted to even be there. The mystery revolves around strange shadow-like spokes that appeared on Saturn's large B-ring, the large middle ring in the complex system of particles that orbits Saturn. The spokes were discovered 23 years ago by the passing Voyager spacecraft and attributed to very fine dust of unknown origin. The missing spokes were noted in the above image, taken last month, from the robot Cassini spacecraft now approaching Saturn. Launched in 1997, the distance remaining between Cassini and Saturn is now less than half that between the Earth and the Sun. Cassini is expected to enter orbit around the ringed Jovian giant planet in July and drop a probe onto Titan, Saturn's largest moon.

APOD: 2004 February 14 - Solar System Portrait
Explanation: On another Valentine's Day (February 14, 1990), cruising four billion miles from the Sun, the Voyager 1 spacecraft looked back to make this first ever family portrait of our Solar System. The complete portrait is a 60 frame mosaic made from a vantage point 32 degrees above the ecliptic plane. Voyager's wide angle camera frames sweep through the inner Solar System (far left) linking up with gas giant Neptune, at the time the Solar System's outermost planet (scroll right). Positions for Venus, Earth, Jupiter, Saturn, Uranus, and Neptune are indicated by the corresponding letters while the Sun is the bright spot near the center of the circle of frames. The inset frames for each of the planets are from Voyager's narrow field camera. Unseen in the portrait are Mercury, too close to the Sun to be detected, and Mars, unfortunately hidden by sunlight scattered in the camera's optical system. Small, faint Pluto's position was not covered.

APOD: 2003 December 25 - Venus and the 37 Hour Moon
Explanation: At Table Mountain Observatory, near Wrightwood California, USA on October 26, wild fires were approaching from the east. But looking toward the west just after sunset, astronomer James Young could still enjoy this comforting view of a young crescent Moon and brilliant Venus through the the fading twilight. Setting over the horizon of Mt. Baden-Powell, the thin crescent was only about 37 hours "old", or 37 hours after its exact New Moon phase. After disappearing from morning twilight in August, Venus was becoming prominent in its role in western skies as the evening star. A similar lovely pairing of thin crescent Moon and stunning evening star can be seen toward the west in today's evening twilight. Happy Holidays and Best Wishes from APOD!

APOD: 2003 December 4 - New Horizons at Jupiter
Explanation: Headed for the first close-up exploration of the Pluto-Charon system and the icy denizens of the Kuiper belt, NASA's New Horizons spacecraft is pictured here in an artist's vision of the robot probe outward bound. The dramatic scene depicts the 465 kilogram spacecraft about one year after a planned 2006 launch, following a flyby of gas giant Jupiter. While the Jupiter flyby will be used as a gravity assist maneuver to save fuel and cut travel time to the outer reaches of the Solar System, it will also provide an opportunity to test instruments and study the giant planet, its moons, and magnetic fields. The Sun is seen from eight hundred million kilometers away, with inner planets Earth, Venus, and Mercury aligned on the left. A dim crescent of outermost Galilean moon Callisto, orbiting Jupiter just inside of the spacecraft's trajectory, appears to the upper right of the fading Sun. Left of Jupiter itself is Europa and in the distant background are the faint, unresolved stars and dust clouds of the Milky Way. New Horizons' planned arrival at Pluto-Charon is in the summer of 2015.

APOD: 2003 November 30 - A Venus Landing
Explanation: This image is part of the first color panoramic view from Venus. A TV camera on the Soviet Venera 13 lander that parachuted to the surface on 1982 March 1 transmitted it. Venus' clouds are composed of sulfuric acid droplets while its surface temperature is about 482 degrees Celsius at an atmospheric pressure of 92 times that of sea-level on Earth. Despite these harsh conditions, the Venera 13 lander survived long enough to send back a series of images and perform an analysis of the Venusian soil. Part of the lander itself is visible in the lower right portion of the image. An earlier Soviet Venus lander, Venera 7 (1970), was the first spacecraft to return data from the surface of another planet.

APOD: 2003 October 21 - The Belt of Venus over the Valley of the Moon
Explanation: Although you've surely seen it, you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly off-color, slightly pink. Called the Belt of Venus, this off-color band between the dark eclipsed sky and the blue sky can be seen in nearly every direction including that opposite the Sun. Straight above, blue sky is normal sunlight reflecting off the atmosphere. In the Belt of Venus, however, the atmosphere reflects light from the setting (or rising) Sun which appears more red. The Belt of Venus can be seen from any location with a clear horizon. Pictured above, the Belt of Venus was photographed above morning fog in the Valley of the Moon, a famous wine-producing region in northern California, USA. The belt is frequently caught by accident in other photographs.

APOD: 2003 August 22 - Shadow Rise
Explanation: As the Sun sets, the Earth's shadow rises up from the east. The subtle beauty of this daily apparition is often overlooked in favor of the brighter, more colorful western horizon. But while gazing toward a nearly full rising Moon on August 9, astronomer Steve Mandel admired the shadow rise from his driveway near Soquel, California, USA. His view looks east from the northern tip of Monterey Bay toward Fremont Peak, the highest point in the small mountain range on the horizon. The Earth's rising shadow is cast through the dense atmosphere and is seen in his picture as the dark blue band along the horizon, bounded above by a pinkish purple glow or antitwilight arch. Also known as the Belt of Venus, the arch's lovely color is due to backscattering of reddened light from the setting Sun.

APOD: 2003 August 13 - Mars Rising Behind Poodle Rock
Explanation: Have you seen Mars lately? As Earth and Mars near their closest approach in nearly 60,000 years on August 27, the red planet has begun to appear dramatically bright and show interesting details through telescopes and binoculars. Although not yet visible at sunset, Mars can be seen rising increasingly earlier in the evening. Once above the horizon, Mars is easy to spot, as it sports a distinct orange-red hue and it is the brightest object in the sky after the Sun, the nearby Moon, and Venus. After Earth overtakes Mars in their respective solar orbits, Mars will be visible right from sunset, although its historic brightness will then begin to fade. Pictured above, Mars was captured rising in the south east next to Poodle Rock in Valley of Fire State Park, Nevada, USA.

APOD: 2003 May 14 - The North Pole of Venus
Explanation: If you could look down on the North Pole of Venus what would you see? The Magellan probe that orbited Venus from 1990 to 1994 was able to peer through the thick Venusian clouds and build up the above image by emitting and re-detecting cloud-penetrating radar. Visible as the bright patch below central North is Venus' highest mountain Maxwell Montes. Other notable features include numerous mountains, coronas, impact craters, tessera, ridges, and lava flows. Although the size and mass of Venus are similar to the Earth, its thick carbon-dioxide atmosphere has trapped heat so efficiently that surface temperature usually exceeds 700 kelvins, hot enough to melt lead.

APOD: 2003 May 8 - Mercury Spotting
Explanation: Can you spot the planet? The diminutive disk of Mercury, the solar system's innermost planet, spent about five hours crossing in front of the enormous solar disk yesterday (Wednesday, May 7th), as viewed from the general vicinity of planet Earth. The Sun was above the horizon during the entire transit for observers in Europe, Africa, Asia, or Australia, and the horizon was certainly no problem for the sun-staring SOHO spacecraft. Seen as a dark spot, Mercury progresses from left to right (top panel to bottom) in these four images from SOHO's extreme ultraviolet camera. The panels' false-colors correspond to different wavelengths in the extreme ultraviolet which highlight regions above the Sun's visible surface. This is the first of 14 transits of Mercury which will occur during the 21st century, but the next similar event will be a transit of Venus in June of 2004. Need help spotting Mercury? Just click on the picture.

APOD: 2003 April 27 - Venus' Once Molten Surface
Explanation: If you could look at Venus with radar eyes - this is what you might see. This computer reconstruction of the surface of Venus was created from data from the Magellan spacecraft. Magellan orbited Venus and used radar to map our neighboring planet's surface between 1990 and 1994. Magellan found many interesting surface features, including the large circular domes, typically 25-kilometers across, that are depicted above. Volcanism is thought to have created the domes, although the precise mechanism remains unknown. Venus' surface is so hot and hostile that no surface probe has lasted more than a few minutes.

APOD: 2003 March 28 - 1006 AD: Supernova in the Sky
Explanation: A new star, likely the brightest supernova in recorded human history, appeared in planet Earth's sky in the year 1006 AD. The expanding debris cloud from the stellar explosion is still visible to modern astronomers, but what did the supernova look like in 1006? Astronomer Tunç Tezel offers this suggestion, based on a photograph he took on February 22, 1998 from a site overlooking the Mediterranean south of Antalya, Turkey. On that date, bright Venus and a waning crescent Moon shone in the early morning sky. Adopting recent calculations which put the supernova's apparent brightness between Venus and the crescent Moon, he digitally superposed an appropriate new star in the picture. He placed the star at the supernova's position in the southerly constellation of Lupus and used the water's reflection of moonlight in the final image. Tezel hopes to view the total solar eclipse of 29 March 2006 from this same site -- on the 1,000th anniversary of Supernova 1006.

APOD: 2003 March 17 - SN 1006: History's Brightest Supernova
Explanation: Suddenly, in the year 1006 AD, a new star appeared in the sky. Over the course of just a few days, the rogue star became brighter than the planet Venus. The star, likely the talk of everyone who could see it, was recorded by people who lived in areas now known as China, Egypt, Iraq, Italy, Japan, and Switzerland. The celestial newcomer, now known to be a supernova, took months to fade. Modern observations have been used to measure the speed of the still-expanding shock wave, allowing a better estimate of its distance and hence a better estimate of the true brightness of the supernova. It turns out SN 1006 likely achieved an apparent visual magnitude of -7.5, making it the brightest supernova on record. The shock wave was imaged in 1998 from CTIO (left panel), and then subtracted from a similar image taken in 1986 (right panel), highlighting the relative expansion.

APOD: 2002 December 4 - Moon, Mars, Venus, and Spica
Explanation: Gliding toward today's total eclipse of the Sun, the crescent Moon has been rising early, just before dawn. And as a prelude to its close solar alignment, the Moon also completed a lovely celestial triangle, closing with bright planets Mars and Venus on the morning of December 1. While the total solar eclipse can only be seen from a narrow corridor, skygazers around the globe could appreciate this lunar-planetary conjunction. This view is from near Nashville Tennessee, USA, and finds brilliant Venus at the lowest corner of the triangle with a much fainter Mars immediately to the right of the Moon. The Moon's sunlit crescent is overexposed, but details of the lunar night side are revealed by earthshine. Above and to the right of the trio is Spica, brightest star in the constellation Virgo.

APOD: 2002 September 29 - Venus: Just Passing By
Explanation: Venus, the second closest planet to the Sun, is a popular way-point for spacecraft headed for the gas giant planets in the outer reaches of the solar system. Why visit Venus first? Using a "gravity assist " maneuver, spacecraft can swing by planets and gain energy during their brief encounter saving fuel for use at the end of their long interplanetary voyage. This colorized image of Venus was recorded by the Jupiter-bound Galileo spacecraft shortly after its gravity assist flyby of Venus in February of 1990. Galileo's glimpse of the veiled planet shows structure in swirling sulfuric acid clouds. The bright area is sunlight glinting off the upper cloud deck. A recent intriguing but controversial hypothesis holds that living microbes might exist in the upper clouds of Venus.

APOD: 2002 September 10 - Venus Beyond the Storm
Explanation: A thunderstorm, lightning, a bright star and a bright planet all graced an evening sky for a short while near Bismarck, North Dakota, USA two weeks ago. Thick thunderclouds from a passing storm are the origin of a strong cloud to ground lightning strike. Small areas of rain darken portions of the orange sunset, visible at the horizon above the vast prairie. The planet Venus peeks below the clouds on the lower left of the image. Blue sky shines high above the distant storm, streaked with high white cirrus clouds. The bright star Arcturus glitters near the image top, just left of center. Just a few minutes later, only a memory and this picture remained.

APOD: 2002 July 26 - Clearing Skies
Explanation: Clear evening skies are a welcome sight for stargazers worldwide, but clearing skies are good too. Just such a glorious occasion was recorded in this dramatic photo taken by Dominic Cantin during a recent gathering of Canadian astronomers at St-Nérée Observatory, located about 60 kilometers southeast of the city of Quebec. Looking toward the west on July 13th, the exposure captured a distant lightning flash from a passing thunderstorm at the far left. On the right, the storm clouds' retreat has uncovered an overexposed crescent Moon sharing the evening twilight with bright Venus only a few degrees away (below and far right). In the darkening sky above the young Moon is a familiar right triangle of stars in the constellation Leo. Cantin reports that clear skies followed, all night long.

APOD: 2002 June 25 - Venus and Jupiter Over Belfast
Explanation: Venus and Jupiter appeared to glide right past each other earlier this month. In a slow day-by-day march, Jupiter sank into the sunset horizon while Venus remained high and bright. The conjunction ended the five-planet party visible over the last two months. Jupiter, of course, is much further away from the Earth and Sun than Venus, so the passing was really just an angular illusion. Pictured above on June 3, a fading sunset finds Venus shining over Jupiter above clouds, mountains, and the city lights of Belfast, Northern Ireland.

APOD: 2002 June 19 - The Moon and Venus Over Geneva
Explanation: The Moon, fresh from a biting encounter with the Sun last week, appeared next to threaten Venus. The waxing Moon appeared to glide right past, however, just a few degrees away. Venus, of course, is much further away from the Earth than the Moon, so the passing was really just an angular illusion. Pictured above on June 13, a fading sunset finds the crescent Moon and Venus between clouds and above the city lights of Geneva, Switzerland.

APOD: 2002 May 24 - Love and War by Moonlight
Explanation: Venus, named for the Roman goddess of love, and Mars, the war god's namesake, approach each other by moonlight in this lovely sky view recorded on May 14th from Dunkirk, Maryland, USA. The four second time exposure made in twilight with a digital camera also records earthshine illuminating the otherwise dark surface of the young crescent Moon. Venus shines as the third brightest object in Earth's sky, after the Sun and the Moon itself, and has been appearing as the brilliant evening star in the pantheon of planets arrayed in the west during April and May. Here, Venus' light is so intense that it produces a noticeable spike in the sensitive camera's image. Much fainter Mars is lower in the picture, caught between tree limbs swaying in a gentle evening breeze. By early June, Mars will be harder to spot as it wanders toward the horizon, but Venus and father Jupiter will draw closer together, presenting a spectacular pair of bright planets in the west.

APOD: 2002 May 22 - Moon and Planets by the Eiffel Tower
Explanation: The great evening grouping of planets is coming to an end. Before all the planets went their own separate directions, however, the Moon was kind enough to pose with some of them. The planets in the above picture, taken last week, are Venus and Jupiter. Mars, Saturn, and even Mercury appear to the lower right of Venus but are too dim to be seen. Over the next two weeks, the Moon will rise later and later passing a full phase on May 26. Venus and Jupiter will continue to shine, moving together until their closest approach on June 3. The Eiffel Tower, however, is expected to remain right where it is.

APOD: 2002 May 10 - Trailing Planets
Explanation: Positioning his camera and tripod on planet Earth, near Maricopa, Arizona, USA, astrophotographer Joe Orman created this trailing display of the ongoing sky-full-of-planets on May 3rd. He initially captured the grouping in a 20 second long time exposure recording the positions of the bright planets and stars. Covering the camera lens for five minutes, he then exposed the same frame for 45 minutes, tracing the gentle arcs of the celestial wanderers as the Earth's rotation carried them toward the western horizon. Of course these planets, Mercury, Venus, Mars, Jupiter, and Saturn all still dazzle in western skies near sunset, but sky gazers who want to see Mercury should look soon. Mercury starts the evening closest to the horizon - visible here above the wide bright trail left by Venus - and in the coming days Mercury will be the first to leave the evening sky entirely as it moves closer to the setting Sun. Tonight Venus and Mars will appear very close together, separated by only one third of a degree.

APOD: 2002 May 9 - Planets Over Stonehenge
Explanation: Stonehenge, four thousand year old monument to the Sun, provides an appropriate setting for this delightful snapshot of the Sun's children gathering in planet Earth's sky. While the massive stone structure dates from around 2000 B.C., this arrangement of the visible planets was recorded only a few days ago on the evening of May 4th, 2002 A.D. Bright Jupiter stands highest above the horizon at the upper left. A remarkable, almost equilateral triangle formed by Saturn (left), Mars (top), and Venus (right) is placed just above the stones near picture center. Fighting the glow of the setting sun, Mercury can be spotted closest to the horizon, below and right of the planetary triad. Still easy to enjoy for casual sky gazers, this photogenic and slowly shifting planetary grouping will be joined by a young crescent Moon beginning Monday, May 13.

APOD: 2002 April 29 - Dusk of the Planets
Explanation: A great grouping of planets is now visible to the west just after sunset. Over the next two weeks, Mercury, Venus, Earth, Mars, Jupiter, and Saturn -- the innermost six planets of our Solar System -- can be seen in a single knowing glance. The image on the left captured them all in one frame. Connecting the planetary dots delineates the edge-on ecliptic, the plane in which the planets orbit the Sun. The shot was taken on April 23 near Chatsworth, New Jersey, USA, and even includes scattered light from the Sun and the Moon. Besides the planets, the Pleiades and Hyades open clusters of stars are visible.

APOD: 2002 April 18 - Planets in the West
Explanation: Have you seen any bright planets lately? Chances are if you've been outside under clear skies just after sunset, then you have. Now shining in the west as bright "stars" in the night sky, are all five planets of the solar system known to ancient astronomers - Mercury, Venus, Mars, Saturn, and Jupiter. Recorded from Holt, Michigan, USA about 40 minutes after sunset on April 14th, this digital image captures three of them, Venus, Mars, and Saturn, along with a young crescent Moon. Also indicated are the Pleiades star cluster and bright red giant star Aldebaran in Taurus. Mercury, setting, is lost in the trees and glow along the horizon, while Jupiter is off the top of this view. The coming weeks will see photo opportunities galore as all five planets gradually move closer together, posing after sunset with the Moon and stars in the western sky. Venus, Mars, and Saturn will form the closest trio, drawing within a 5 degree circle (about the apparent size of your fist with arm extended) above Aldebaran by May 3rd.

APOD: 2002 March 30 - Venus Unveiled
Explanation: The surface of Venus is perpetually covered by a veil of thick clouds and remains hidden from even the powerful telescopic eyes of earth-bound astronomers. But in the early 1990s, using imaging radar, the Venus orbiting Magellan spacecraft was able to lift the veil from the face of Venus and produced spectacular high resolution images of the planet's surface. Colors used in this computer generated picture of Magellan radar data are based on color images from the surface of Venus transmitted by the Soviet Venera 13 and 14 landers. The bright area running roughly across the middle represents the largest highland region of Venus known as Aphrodite Terra.

APOD: 2002 March 12 - Atete Corona on Venus
Explanation: What could cause a huge cylindrical mountain to rise from the surface of Venus? Such features that occur on Venus are known as coronas. Pictured above in the foreground is 500-kilometer wide Atete Corona found in a region of Venus known as the Galindo. The image was created by combining multiple radar maps of the region to form a computer-generated three-dimensional perspective. The series of dark rectangles that crosses the image from top to bottom were created by the imaging procedure and are not real. The origin of massive coronas remains a mystery although speculation holds they result from some form of volcanism. Studying Venusian coronas help scientists better understand the inner structure of both Venus and Earth.

APOD: 2002 February 14 - Solar System Portrait
Explanation: On another Valentine's Day (February 14, 1990), cruising four billion miles from the Sun, the Voyager 1 spacecraft looked back to make this first ever family portrait of our Solar System. The complete portrait is a 60 frame mosaic made from a vantage point 32 degrees above the ecliptic plane. Voyager's wide angle camera frames sweep through the inner Solar System (far left) linking up with gas giant Neptune, at the time the Solar System's outermost planet (scroll right). Positions for Venus, Earth, Jupiter, Saturn, Uranus, and Neptune are indicated by the corresponding letters while the Sun is the bright spot near the center of the circle of frames. The inset frames for each of the planets are from Voyager's narrow field camera. Unseen in the portrait are Mercury, too close to the Sun to be detected, and Mars, unfortunately hidden by sunlight scattered in the camera's optical system. Small, faint Pluto's position was not covered.

APOD: 2002 January 11 - Sunbather
Explanation: Intense and overwhelming, the direct glare of the Sun is blocked by the smooth disk centered in this image from the sun-staring SOHO spacecraft. Taken on January 8, the picture shows streamers of solar wind billowing radially outward for millions of kilometers above the Sun's surface indicated by the white circle. Below and right is inner planet Venus, so bright that its image is marred by a sharp horizontal stripe, a digital imaging artifact. Also impressively bright is a periodic visitor to the inner Solar System, sunbathing comet 96/P Machholz 1 (above and left). This comet is definitely not a member of the more suicidal sungrazer comet family often spotted approaching the Sun by SOHO. Seen here only 18 million kilometers from the Sun (about one eighth the Earth-Sun distance) with a substantial coma and foreshortened tail, Machholz 1 has now passed perihelion and is outbound in its orbit, to return again in just over 5 years.

APOD: 2001 December 11 - Venusian Half Shell
Explanation: Venus, second planet from the Sun, appears above imaged for the first time ever in x-rays (left) by the orbiting Chandra Observatory. Chandra's smoothed, false-color, x-ray view is compared to an optical image (right) from a small earthbound telescope. Both show Venus illuminated by the Sun from the right, with only half the sunward hemisphere visible, but at least one striking difference is apparent. While the optical image in reflected sunlight is filled and bright at the center, Venus in x-rays is bright around the edge. Venus' x-rays are produced by fluorescence rather than reflection. About 120 kilometers or so above the surface, incoming solar x-rays excite atoms in the Venusian atmosphere to unstable energy levels. As the atoms rapidly decay back to their stable ground states they emit a "fluorescence" x-ray, creating a glowing x-ray half-shell above the sunlit hemisphere. More x-ray emitting material can be seen looking at the edge of the shell, so the edge appears brighter in the x-ray image.

APOD: 2001 December 9 - The Belt of Venus
Explanation: Although you've surely seen it, you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly off-color, slightly pink. Visible in the above photograph, this off-color band between the dark eclipsed sky and the blue sky can best be seen in the direction opposite the Sun and is called the Belt of Venus. Straight above, blue sky is normal sunlight reflecting off the atmosphere. In the Belt of Venus, however, the atmosphere reflects light from the setting (or rising) Sun which appears more red. The Belt of Venus can be seen from any location with a clear horizon. It is frequently caught by accident in other photographs.

APOD: 2001 October 15 - The Earth and Moon Planetary System
Explanation: How similar in size are the Earth and the Moon? A dramatic visual answer to this question is found by combining photographs taken by the Mariner 10 spacecraft that headed out toward Venus and Mercury in 1973. The Moon can be seen to have a diameter over one quarter that of Earth, relatively large compared to its planetary companion. In our Solar System, only Pluto and Charon are closer together in size. Striking features of the Earth visible to the passing spacecraft include blue oceans and white clouds, showing the Earth to be truly a water world.

APOD: 2001 September 16 - Venus Once Molten Surface
Explanation: If you could look at Venus with radar eyes - this is what you might see. This computer reconstruction of the surface of Venus was created from data from the Magellan spacecraft. Magellan orbited Venus and used radar to map our neighboring planet's surface between 1990 and 1994. Magellan found many interesting surface features, including the large circular domes, typically 25-kilometers across, that are depicted above. Volcanism is thought to have created the domes, although the precise mechanism remains unknown. Venus' surface is so hot and hostile that no surface probe has lasted more than a few minutes.

APOD: 2001 August 26 - Uranus: The Tilted Planet
Explanation: Uranus is the third largest planet in our Solar System after Jupiter and Saturn. Uranus is composed mostly of rock and ices, but with a thick hydrogen and helium atmosphere. The blue hue of Uranus' atmosphere arises from the small amount of methane which preferentially absorbs red light. This picture was snapped by the Voyager 2 spacecraft in 1986 - the only spacecraft ever to visit Uranus. Uranus has many moons and a ring system. Uranus, like Venus, has a rotation axis that is greatly tilted and sometimes points near the Sun. It remains an astronomical mystery why Uranus' axis is so tilted. Uranus and Neptune are quite similar: Uranus is slightly larger but less massive.

APOD: 2001 August 7 - A July Dawn
Explanation: Those up before dawn in late July in the northern hemisphere could see planets, stars, and a spacecraft in a single quick glance before starting their day. Near the eastern horizon was bright Jupiter, and not far above and to its right was the very bright Venus. Connecting the dots will point you just right of Saturn. Far in the distance but near the top right of the frame is the Pleiades star cluster. Orbiting the Earth well in the foreground, the International Space Station reflected sunlight to cause the faint line segment. In the very close foreground, the bright red and yellow lines were caused by a passing van. The above picture was taken on July 26 from Quebec, Canada. Why are bushes visible through the van? The van was present for only a few of the 25 seconds of the total exposure.

APOD: 2001 June 1 - Venus' Evening Loop
Explanation: From September 2000 through March 2001, astronomer Tunc Tezel patiently photographed the planet Venus on 25 different dates as it wandered through the evening twilight. The pictures were taken from the same spot on the campus of the Middle East Technical University near Ankara, Turkey, and timed so that for each photo the Sun was 7 degrees below the horizon. Carefully registering and combining the pictures, he produced this composite image -- a stunning demonstration of Venus' grand looping sky motion during its recent stint as planet Earth's evening star. As indicated, the first picture, taken September 28, 2000, finds Venus close to the western horizon and drifting south (left) with the passing days. By December however, Venus was climbing well above the horizon after sunset and in January 2001 it reached its maximum apparent distance (elongation) from the Sun. March found Venus falling from the evening sky while moving rapidly north, finally appearing (far right) as a faint dot against the sunset glow on March 24. This month, Venus rises before dawn as the brilliant morning star.

APOD: 2001 May 15 - A Radar Image of Venus
Explanation: The largest radio telescopes in the world are working together to create a new map of the surface of Venus. The surface of Venus is unusually hidden by a thick atmosphere of mostly carbon dioxide gas. These thick clouds are transparent, however, to radar signals sent and received from Earth. The two radio telescopes generating the most powerful radar ever are the Arecibo Telescope in Puerto Rico and the new Robert C. Byrd Green Bank Telescope in West Virginia. The new survey will resolve details as fine a one-kilometer across, and will be inspected for changes since the last major radar map was made by NASA's Magellan spacecraft that orbited Venus from 1990 to 1994. Pictured above is part of a preliminary image showing details as small as five-kilometers across.

APOD: 2001 May 7 - One Hundred Kilometer Terrain on Venus
Explanation: Even the hot and cracked surface of Venus has rolling hills. Although never actually photographed from up-close, images of the Venusian surface like that shown above have been constructed in recent years by digitally merging distant photographs from height-sensitive radar. Isolated above is a 100-kilometer wide swath inside a volcanic region known as Yavine Corona. Visible in the frame are numerous fractures in the surface. Data is missing from the dark lane on the upper right. The surface of Venus is so hot and oppressive that robot spacecraft landed there have lasted for only a few hours.

APOD: 2001 March 8 - Bright Venus
Explanation: Have you seen a bright evening star in the western sky lately? That's no star, that's planet Venus the second "rock" from the Sun. Blazing at -4.6 magnitude, Venus, after the Sun and Moon, is the third brightest celestial body in planet Earth's sky. Venus is closer to the Sun than Earth and as Venus orbits the Sun it is seen to go through phases similar to the Moon. But unlike the Moon, as Venus waxes and wanes its distance from Earth and hence its apparent size changes drastically. This causes Venus to look brighter as it looms large in its crescent phases than when it is smaller and nearly full. Taken on January 28th, this dramatic picture finds a crescent Venus near its brightest to the right of a crescent Moon. The brilliant rivals seem poised above a satellite dish of the Scripps Satellite Oceanography Facility. Closer to the horizon, just below and to the right of the satellite dish, Mercury pierces the twilight glow.

APOD: 2001 February 9 - Nashville Four Planet Skyline
Explanation: So far this February, evening skies have been blessed with a glorious Moon and three bright planets; Venus, Jupiter, and Saturn. But just last week, on January 30th, an extreme wide-angle lens allowed astrophotographer Larry Koehn to capture this twilight view of Moon and four planets above Nashville, Tennessee, USA. These major solar system bodies lie along the ecliptic plane and so follow a diagonal line through the picture. Starting near the upper left corner is bright Jupiter, which takes on a slightly triangular shape due to the lens distortion. Just below and right of Jupiter is Saturn. Continuing along the diagonal toward the lower right is an overexposed, six day old Moon and brilliant Venus seemingly embedded in clouds. The fourth planet pictured is Mercury. Notoriously hard to see from planet Earth because it never wanders far from the Sun, Mercury is visible just above the lower right corner. The line from Jupiter to Mercury spans about 92 degrees across the Nashville sky.

APOD: 2000 December 14 - International Space Station Trail
Explanation: Still under construction, the International Space Station is becoming one of the brightest, fastest moving "stars" in the heavens. Despite illuminated clouds and bright light from a nearly full moon (lower left), this 5 minute time exposure easily captures the Space Station's trail as it arcs through early evening skies above Palm Beach Gardens, Florida, USA on December 9. At the time, the Space Shuttle Endeavour had undocked and moved away from the orbiting platform, the shuttle crew having just completed the installation of large solar panels to power the Space Station's systems. Sunlight glinting off the large, shiny panels is likely the source of the brief flare visible along the track. Astrophotographer Doug Murray and colleague report that both Shuttle and Space Station were visible separately and on close inspection of this image they do produce distinct, parallel arcs. At the extreme right hand edge of the picture, the trails pass very near the brightest "star" in the night sky, Venus.

APOD: 2000 November 8 - October Skylights
Explanation: With brilliant Venus above the western horizon at sunset and Jupiter and Saturn high in the east by early evening, November's night sky is filled with bright planets. October's sky featured bright planets as well and, triggered by the active Sun, some lovely auroral displays. This colorful aurora was recorded by astrophotographer Wade Clark in skies above Hamilton, Washington, USA on the night of October 4th. Through the shimmering northern lights Jupiter and Saturn are easy to spot flanking the V-shaped head of Taurus the Bull. Of course, just above lies the lovely Pleiades star cluster. Solar activity will also produce auroral shows in November, particularly at high northern and southern latitudes. Plus, November skygazers can certainly anticipate a celestial performance on the evening of the 17th/18th -- the moonlit Leonid meteor shower.

APOD: 2000 September 27 - Yepun
Explanation: Pictured above on September 3rd, the enclosure for the 8.2 meter telescope christened Yepun glints dramatically in the light of the setting sun. Later that evening, under dark skies at Paranal Observatory, Chile, astronomers and engineers successfully captured Yepun's first light images, making Yepun the fourth and final unit of the European Southern Observatory's Very Large Telescope (VLT) array to reach this milestone. Ultimately, the light from the three other 8.2 meter unit telescopes (Antu, Kueyen, and Melipal) will be combined with Yepun's to achieve an effective aperture of 16.4 meters -- creating the world's largest optical telescope. But the next major step will be to combine beams from two of the telescopes creating an interferometer. The upper part of the mostly subterranean interferometer lab is the building in front of the telescope enclosure. The VLT unit telescope names have been taken from the Mapuche language. Originally thought to refer to the bright star Sirius, the word Yepun is now believed by linguists to mean Venus or evening star.

APOD: 2000 July 28 - Moon And Venus Share The Sky
Explanation: July is drawing to a close and in the past few days, some early morning risers could have looked east and seen a crescent Moon sharing the pre-dawn skies with planets Jupiter and Saturn. Planet Mercury will also pass about 2 degrees from the thin waning crescent Moon just before sunrise near the eastern horizon on Saturday, July 29. And finally, on the evening of July 31st, Venus will take its turn near the crescent Moon. But this time it will be a day-old crescent Moon near the western horizon, shortly after sunset. In fact, on July 31 (August 1 Universal Time) the Moon will occult (pass in front of) Venus for northwestern observers in North America. This telescopic picture taken on 31 December 1997, shows a lovely young crescent Moon and brilliant crescent Venus in the early evening sky near Bursa, Turkey.

And what about the Sun? On Sunday, July 30, a partial eclipse of the Sun will be visible from some locations in North America.

APOD: 2000 July 17 - Lightning on Earth
Explanation: Nobody knows what causes lightning. It is known that charges slowly separate in some clouds causing rapid electrical discharges (lightning), but how electrical charges get separated in clouds remains a topic of much research. Nevertheless, lightning bolts are common in clouds during rainstorms, and on average 6000 lightning bolts occur between clouds and the Earth every minute. Above, several lightning strokes were photographed behind Kitt Peak National Observatory in Arizona. Lightning has also been found on the planets Venus, Jupiter, Saturn, and Uranus. NASA launched the TRMM mission in 1997 that continues to measure rainfall and lightning on planet Earth.

APOD: 2000 May 24 - Pleiades, Planets, And Hot Plasma
Explanation: Bright stars of the Pleiades, four planets, and erupting solar plasma are all captured in this spectacular image from the space-based SOlar and Heliospheric Observatory (SOHO). In the foreground of the 15 degree wide field of view, a bubble of hot plasma, called a Coronal Mass Ejection (CME), is blasting away from the active Sun whose position and relative size is indicated by the central white circle. Beyond appear four of the five naked-eye planets -- courtesy of the planetary alignment which did not destroy the world! In the background are distant stars and the famous Pleiades star cluster, also easily visible to the unaided eye when it shines in the night sky. Distances for these familiar celestial objects are; the Sun, 150 million kilometers away; Mercury, Venus, Jupiter, and Saturn, about 58, 110, 780, and 1,400 million kilometers beyond the Sun respectively; and the Pleiades star cluster at a mere 3,800 trillion kilometers (400 light-years). SOHO itself orbits 1.5 million kilometers sunward of planet Earth. The image was recorded by the Large Angle and Spectrometric COronagraph (LASCO) instrument on board SOHO on Monday, May 15 at 10:42 UT.

APOD: 2000 May 5 - Planets In The Sun
Explanation: Today, all five naked-eye planets (Mercury, Venus, Mars, Jupiter, Saturn) plus the Moon and the Sun will at least approximately line-up. As viewed from planet Earth, they will be clustered within about 26 degrees, the closest alignment for all these celestial bodies since February 1962, when there was a solar eclipse! Such planetary alignments are not dangerous, except of course that the Sun might hurt your eyes when you look at it. So it might be easier to appreciate today's solar system spectacle if you use a space-based coronagraph ... like the LASCO instrument onboard the SOHO observatory. In this recent LASCO image, an occulting disk supported by a structure seen projecting from the lower left blocks out the overwhelming sunlight. It shows three of the planets along with the Sun's location and bright solar wind regions against a background of stars, but Mars and Venus are unfortunately outside LASCO's roughly 15 degree field of view. The horizontal bars through the planets are digital image artifacts. And what about the Moon? The SOHO spacecraft is positioned well beyond lunar orbit where its view of the Sun is never interrupted by the Moon.

APOD: 2000 April 6 - Venus, Moon, and Neighbors
Explanation: Rising before the Sun on February 2nd, astrophotographer Joe Orman anticipated this apparition of the bright morning star Venus near a lovely crescent Moon above a neighbor's house in suburban Phoenix, Arizona, USA. Fortunately, the alignment of bright planets and the Moon is one of the most inspiring sights in the night sky and one that is often easy to enjoy and share without any special equipment. Take tonight, for example. Those blessed with clear skies can simply step outside near sunset and view a young crescent Moon very near three bright planets in the west Jupiter, Mars, and Saturn. Jupiter will be the unmistakable brightest star near the Moon with a reddish Mars just to Jupiter's north and pale yellow Saturn directly above. Of course, these sky shows create an evocative picture but the planets and Moon just appear to be near each other -- they are actually only approximately lined up and lie in widely separated orbits. Unfortunately, next month's highly publicized alignment of planets on May 5th will be lost from view in the Sun's glare but such planetary alignments occur repeatedly and pose no danger to planet Earth.

APOD: 2000 March 26 - Venus Once Molten Surface
Explanation: If you could look at Venus with radar eyes - this is what you might see. This computer reconstruction of the surface of Venus was created from data from the Magellan spacecraft. Magellan orbited Venus and used radar to map our neighboring planet's surface between 1990 and 1994. Magellan found many interesting surface features, including the large circular domes, typically 25-kilometers across, that are depicted above. Volcanism is thought to have created the domes, although the precise mechanism remains unknown. Venus' surface is so hot and hostile that no surface probe has lasted more than a few minutes.

APOD: 2000 March 10 - Sky and Planets
Explanation: On February 10th, an evocative evening sky above Rocklin, California, USA inspired astrophotographer Steve Sumner to record this remarkable sight - five planets and the Moon. Near its first quarter phase, the bright Moon was intentionally overexposed but Saturn, Jupiter, Mars, and Mercury (and, of course, planet Earth's horizon) are all clearly visible in the deepening twilight. Notably absent in this grouping of naked-eye planets is Venus which is still putting in an early appearance as the morning star. This month, Mercury has joined Venus in the dawn twilight while Saturn, Jupiter, and Mars still shine brightly in the western sky at nightfall making another gorgeous close grouping with the crescent Moon.

APOD: November 28, 1999 - Beneath Venus Clouds
Explanation: If the thick clouds covering Venus were removed, how would the surface appear? Using an imaging radar technique, the Magellan spacecraft was able to lift the veil from the Face of Venus and produce this spectacular high resolution image of the planet's surface. Red, in this false-color map, represents mountains, while blue represents valleys. This 3-kilometer resolution map is a composite of Magellan images compiled between 1990 and 1994. Gaps were filled in by the Earth-based Arecibo Radio Telescope. The large yellow/red area in the north is Ishtar Terra featuring Maxwell Montes, the largest mountain on Venus. The large highland regions are analogous to continents on Earth. Scientists are particularly interested in exploring the geology of Venus because of its similarity to Earth.

APOD: November 10, 1999 - The Belt of Venus
Explanation: Although you've surely seen it, you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly off-color, slightly pink. Visible in the above photograph, this off-color band between the dark eclipsed sky and the blue sky can best be seen in the direction opposite the Sun and is called the Belt of Venus. Straight above, blue sky is normal sunlight reflecting off the atmosphere. In the Belt of Venus, however, the atmosphere reflects light from the setting (or rising) Sun which appears more red. The Belt of Venus can be seen from any location with a clear horizon.

APOD: November 6, 1999 - X ray Transit of Mercury
Explanation: This sequence of false color X-ray images captures a rare event - the passage or transit of planet Mercury in front of the Sun. Mercury's small disk is silhouetted against the bright background of X-rays from the hot Solar Corona. It appears just to the right of center in the top frame and moves farther right as the sequence progresses toward the bottom. The dark notch is a coronal hole near the Solar South Pole, while a flaring coronal bright point can be seen to the left of the notch in the top frames. The frames were recorded on November 6, 1993 by the Soft X-ray Telescope on board the orbiting Yohkoh satellite. Transits of Mercury (and Venus) were historically used to discover the geometry of the solar system and to map planet Earth itself. The next transit of Mercury will occur on November 15.

APOD: September 3, 1999 - Venus Falls Out of the Evening Sky
Explanation: Orbiting closer to the Sun than planet Earth, bright Venus always appears to be near the Sun's position in our sky and often shines near the horizon in twilight hours. In fact, after posing as the brilliant evening star for the first half of this year, Venus has now swung around its orbit and is emerging in the predawn twilight as the morning star. Taken during its stint as the evening star, this imaginative long-exposure photo, of Venus and a 2-day-old crescent Moon gives the illusion of the pair "falling out" of the western sky. After an initial short exposure captured the Moon and Venus, the lens was covered for a few minutes, then left uncovered to record the trails until the Moon had set.

APOD: June 19, 1999 - Venus on the Horizon
Explanation: Venus can appear as a brilliant evening star. Besides the sun and moon, Venus is the brightest object visible in Earth's sky. Because it is closer to the sun than Earth, Venus never strays far from the sun in its apparent position and is seen during the year as either a bright morning or evening star. This beautiful sunset imaged from low earth orbit by the Atlantis space shuttle crew in May 1989 also reveals the planet Venus blazing above Earth's horizon. It is a fitting image for this mission and crew. It was recorded following the successful release of the robot Venus-explorer Magellan, the first planetary probe to be deployed from a space shuttle.

APOD: June 12, 1999 - Venus: Just Passing By
Explanation: Venus, the second closest planet to the Sun, is a popular way-point for spacecraft headed for the gas giant planets in the outer reaches of the solar system. Why visit Venus first? Using a " gravity assist " maneuver, spacecraft can swing by planets and gain energy during their brief encounter saving fuel for use at the end of their long interplanetary voyage. This colorized image of Venus was recorded by the Jupiter-bound Galileo spacecraft shortly after its gravity assist flyby of Venus in February of 1990. Galileo's glimpse of the veiled planet shows structure in swirling sulfuric acid clouds. The bright area is sunlight glinting off the upper cloud deck. The Saturn-bound Cassini spacecraft will complete its own second flyby of Venus on June 24th. Launched in October of 1997, Cassini should reach Saturn in July 2004.

APOD: May 21, 1999 - Star Party Trails
Explanation: Stargazing is fun! If you'd like to try it, this weekend may be your chance as many astronomy clubs and organizations will be hosting public celebrations of Astronomy Day on Saturday, May 22nd. In recent years, open house nights at observatories, astronomy club gatherings, and star parties have become increasingly popular. They offer great opportunities for beginners to view the sky through a variety of telescopes and veterans to swap stories and ideas. This time exposure of star trails was made last month at the Sentinel, Arizona "Stargaze" star party. On the right, a brilliant trail tracks the setting evening star, Venus. Stars in Orion are near the center and bright Sirius produced the prominent trail at the left. City lights from nearby Yuma glow on the horizon while party-goers' red filtered flashlights create the eerie foreground effect. The red flashlights are courteously used to provide a safe level of illumination but still preserve night vision for enjoyable stargazing.

APOD: May 18, 1999 - A Laguna Triangle
Explanation: High above Laguna Beach last month hung bright celestial orbs. Visible after the California sunset were, from left to right, the Moon, Saturn, and Venus. Tonight and for the next few days, Venus and the Moon will again be visible together. Nearby stars will include Pollux, Castor, and Procyon. Venus now sets hours after the Sun and is so bright it might be mistaken for an airplane or UFO. Binoculars should enable the viewing of craters on the Moon, and phases for Venus.

APOD: May 5, 1999 - A Solar System Portrait
Explanation: As the Voyager 1 spacecraft headed out of our Solar System, it looked back and took a parting family portrait of the Sun and planets. From beyond Pluto, our Solar System looks like a bright star surrounded by faint dots. In the above picture, the Sun is so bright it is blocked out for contrast. The innermost dots visible, labeled E and V for Earth and Venus, are particularly hard to discern. Gas giants Jupiter (J) and Saturn (S) are much more noticeable. The outermost planets visible are Uranus (U) and Neptune (N). Each planet is shown labeled and digitally enhanced in an inset image. Voyager 1 is only one of four human-made objects to leave our Solar System, the other three being Voyager 2, and Pioneer 10 and Pioneer 11.

APOD: April 18, 1999 - Moon Over California
Explanation: The Moon, Saturn, and Venus shine above while city lights twinkle below in the deepening twilight of March 19. Taken from outside Indio, California, the photo shows the city lights of Indio and nearby Palm Springs. The brilliant lunar crescent is over exposed here with Saturn about 4 degrees away to the upper right and bright Venus still farther to the right only another 2 degrees or so. This Sunday evening, April 18, another dramatic lunar spectacle should be easily visible to stargazers in the western and midwestern US when the crescent moon passes in front of the bright star Aldebaran.

APOD: March 25, 1999 - March of the Planets
Explanation: This March stargazers have been treated to eye-catching formations of bright planets in western evening skies. On March 3rd, looking toward a beautiful sunset from a beach on the Hawaiian isle of Maui, photographer Rick Scott recorded this fleeting, four-planet "hockey stick" array. Mercury, closest to the horizon and immersed in fading sunlight, is easily visible between silhouetted clouds. To the left and up in the deepening blue is Jupiter with a brilliant Venus above and Saturn shining in the darkened sky near the top of the image. The planets are seen to lie close to the ecliptic - the apparent path of the sun - which is nearly perpendicular to the horizon for Hawaiian latitudes at this time of year.

APOD: March 8, 1999 - A Jupiter Venus Conjunction
Explanation: Venus and Jupiter appeared unusually close together in the sky last month. The conjunction was easily visible to the unaided eye because Venus appears brighter than any background star. The two planets were not significantly closer in space - Venus just passed nearly in front of Jupiter as seen from the Earth. Visible in the above photograph are actually five planets. The faint dot near the top is Saturn. Venus is the brightest spot near the center, and Jupiter is just above it. Perhaps the hardest to see is Mercury, visible below Venus but above the foreground Earth. A single line nearly connects all the planets, a result of all planets orbiting the Sun in a single plane called the ecliptic.

APOD: January 24, 1999 - A Venus Landing
Explanation: This image is part of the first color panoramic view from Venus. It was transmitted by a TV camera on the Soviet Venera 13 lander which parachuted to thesurface on March 1, 1982. Venus' clouds are composed of sulfuric acid droplets while its surface temperature is about 900 degrees Fahrenheit (482 degrees C) at an atmospheric pressure of 92 times that of sea-level on Earth. Despite these harsh conditions, the Venera 13 lander survived long enough to send back a series of images and perform an analysis of the Venusian soil. Part of the lander itself is visible in the lower right portion of the image. An earlier Soviet Venus lander,Venera 7 (1970), was the first spacecraft to return data from the surface of another planet.

APOD: January 10, 1999 - Venus Once Molten Surface
Explanation: If you could look at Venus with radar eyes - this is what you might see. This computer reconstruction of the surface of Venus was created from data from the Magellan spacecraft. Magellan orbited Venus and used radar to map our neighboring planet's surface between 1990 and 1994. Magellan found many interesting surface features, including the large circular domes, typically 25-kilometers across, that are depicted above. Volcanism is thought to have created the domes, although the precise mechanism remains unknown. Venus' surface is so hot and hostile that no surface probe has lasted more than a few minutes.

APOD: September 13, 1998 - Galileo Demonstrates the Telescope
Explanation: Galileo Galilei made a good discovery great. Upon hearing at age 40 that a Dutch optician had invented a glass that made distant objects appear larger, Galileo crafted his own telescope and turned it toward the sky. Galileo quickly discovered that our Moon had craters, that Jupiter had its own moons, that the Sun has spots, and that Venus has phases like our Moon. Galileo, who lived from 1564 to 1642, made many more discoveries. Galileo claimed that his observations only made sense if all the planets revolved around the Sun, as championed by Aristarchus and Copernicus, not the Earth, as was commonly believed then. The powerful Inquisition made Galileo publicly recant this conclusion, but today we know he was correct.

APOD: August 25, 1998 - Moon, Venus, Jupiter, Phoenix
Explanation: Before a relaxing sunrise, the sky begins to glow with unusual delights. Such was the view from Papago Park in Phoenix, Arizona this April. The glittering objects visible in this photograph are, from lower left to upper right: Phoenix, our Moon, Venus, and Jupiter. Such proximity is somewhat unusual. Jupiter will be visible in the evening sky through the rest of the year, while Venus can be seen in the early morning sky during the month of September.

APOD: July 2, 1998 - X-ray Transit of Mercury
Explanation: This sequence of false color X-ray images captures a rare event - the passage or transit of planet Mercury in front of the Sun. Mercury's small disk is silhouetted against the bright background of X-rays from the hot Solar Corona. It appears just to the right of center in the top frame and moves farther right as the sequence progresses toward the bottom. The dark notch is a coronal hole near the Solar South Pole, while a flaring coronal bright point can be seen to the left of the notch in the top frames. The frames were recorded on November 6, 1993 by the Soft X-ray Telescope on board the orbiting Yohkoh satellite. Transits of Mercury (and Venus) were historically used to discover the geometry of the solar system and to map planet Earth itself.

APOD: May 17, 1998 - Our Solar System from Voyager
Explanation: After taking spectacular pictures of our Solar System's outer planets, Voyager 1 looked back at six planets to take our Solar System's first family portrait. Here Venus, Earth, Jupiter, Saturn, Uranus, and Neptune, were all visible across the sky. Each, however, was now just a small speck of light, dimmer than many of the stars in the sky. Voyager 1 is only one of four human-made objects to leave our Solar System, the other three being Voyager 2, and Pioneer 10 and Pioneer 11.

APOD: May 13, 1998 - Occultations and Rising Moons
Explanation: On April 23, the rising crescent Moon occulted (passed in front of) Venus and Jupiter. The double occultation was a rare event and only visible from certain locations tracing a path across Earth's surface. This dramatic telephoto picture was taken at one such location, Ascension Island in the South Atlantic. The sunlit crescent is over-exposed revealing the rest of the lunar surface illuminated by faint earthshine. Venus is emerging just beyond the crescent's tip and Jupiter is trailing above the dark lunar edge with a spot of light, Jupiter's moon Ganymede, between the lunar limb and the planet's disk. Look closely at Jupiter and you can see yet another Jovian moon, Io, just visible against Jupiter's glare!

APOD: May 1, 1998 - Venus: Just Passing By
Explanation: Venus, the second closest planet to the Sun, is a popular way-point for spacecraft headed for the gas giant planets in the outer reaches of the solar system. Why visit Venus first? Using a " gravity assist " maneuver, spacecraft can swing by planets and gain energy during their brief encounter saving fuel for use at the end of their long interplanetary voyage. This colorized image of Venus was recorded by the Jupiter-bound Galileo spacecraft shortly after its gravity assist flyby of Venus in February of 1990. Galileo's glimpse of the veiled planet shows structure in swirling sulfuric acid clouds. The bright area is sunlight glinting off the upper cloud deck. The Saturn-bound Cassini spacecraft just completed its own flyby of Venus on April 26. Launched in October of 1997, Cassini should reach Saturn in July 2004.

APOD: April 28, 1998 - A Rare Double Conjunction Eclipse
Explanation: The crescent Moon, Venus, and Jupiter all appeared together in the early morning hours of April 23rd. Some locations on Earth were able to witness a rare double conjunction eclipse, where the Moon occulted both Jupiter and Venus at the same time. The next double conjunction eclipse will involve Mercury and Mars and will occur on February 13, 2056.

APOD: January 20, 1998 - Arachnoids on Venus
Explanation: Arachnoids are large structures of unknown origin that have been found only on the surface of Venus. Arachnoids get their name from their resemblance to spider-webs. They appear as concentric ovals surrounded by a complex network of fractures, and can span 200 kilometers. Radar echoes from the Magellan spacecraft that orbited Venus from 1990 to 1994 built up this image. Over 30 arachnoids have been identified on Venus, so far. The Arachnoid might be a strange relative to the volcano, but possibly different arachnoids are formed by different processes.

APOD: December 4, 1997 - A Sky Full Of Planets
Explanation: Look up tonight. Just after sunset, the crescent moon and all five "naked-eye" planets (Mercury, Venus, Mars, Jupiter, and Saturn) will be visible (depending on your latitude), lying near our solar system's ecliptic plane. Venus and Jupiter will shine brilliantly as the brightest "stars" in the sky, but Mercury will be near the horizon and hard to see. A pair of binoculars will also reveal Uranus and Neptune and observers with a telescope and a good site may even be able to glimpse faint Pluto just above the Western horizon in the fading twilight (not shown on the chart above). Enjoy this lovely spectacle any clear night through about December 8. A similar gathering is expected in May 2000 but the planets will be hidden from view by the solar glare. A night sky as full of planets as this one will occur again though ... in about 100 years.

APOD: October 16, 1997 - Cassini To Venus
Explanation: NASA's Saturn Explorer Cassini with ESA's Titan Probe Huygens attached successfully rocketed into the skies early yesterday morning. The mighty Titan 4B Centaur rocket is seen here across the water gracefully arcing away from Launch Complex 40 at Cape Canaveral Air Station. Cassini, a sophisticated, bus-sized robot spacecraft is now on its way ... to Venus, the first planetary way point in its 7 year, 2.2 billion mile journey to Saturn. The mission profile calls for Cassini to swing by Venus during April 1998 and June 1999, Earth in August 1999, and Jupiter in December 2000. During each of these "gravity assist" encounters the six ton spacecraft will pick up energy needed to reach Saturn in July 2004. Cassini's mission is the most ambitious voyage of interplanetary exploration ever mounted by humanity and the Huygens Probe's planned descent to the surface of Titan will be the most distant landing ever attempted.

APOD: October 14, 1997 - Venus On The Horizon
Explanation: The month of October features a sky full of planets, including Venus as the brilliant evening star. Besides the sun and moon, Venus is the brightest object visible in Earth's sky. This month, Venus appears in early evening near the red planet Mars and Mars' red giant rival Antares above the southwestern horizon. Because it is closer to the sun than Earth, Venus never strays far from the sun in its apparent position and is seen during the year as either a bright morning or evening star. This beautiful sunset imaged from low earth orbit by the Atlantis space shuttle crew in May 1989 also reveals the planet Venus blazing above Earth's horizon. It is a fitting image for this mission and crew. It was recorded following the successful release of the robot Venus-explorer Magellan, the first planetary probe to be deployed from a space shuttle.

APOD: June 9, 1997 - An Auroral Ring on Jupiter
Explanation: Do other planets have aurora? Terrestrial and spacecraft observations have found evidence for aurora on Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. In the above false-color photograph, a good portion of an auroral ring was captured recently in optical light by the Galileo spacecraft in orbit around Jupiter. Auroral rings encircle a planet's magnetic pole, and result from charged particles spiraling down magnetic field lines. Although the surroundings near Jupiter are much different than Earth, the auroral rings appear similar.

APOD: June 3, 1997 - Venus' Once Molten Surface
Explanation: If you could look at Venus with radar eyes - this is what you might see. This computer reconstruction of the surface of Venus was created from data from the Magellan spacecraft. Magellan orbited Venus and used radar to map our neighboring planet's surface between 1990 and 1994. Magellan found many interesting surface features, including the large circular domes, typically 25-kilometers across, that are depicted above. Volcanism is thought to have created the domes, although the precise mechanism remains unknown. Venus' surface is so hot and hostile that no surface probe has lasted more than a few minutes.

APOD: May 12, 1997 - Lightning on Jupiter
Explanation: Does lightning occur only on Earth? Spacecraft in our Solar System have detected radio signals consistent with lightning on other planets, including Venus, Jupiter, Saturn, Uranus, and Neptune. In the above photograph, optical flashes from Jupiter were photographed recently by the Galileo orbiter. Each of the circled dots indicates lightning. The numbers label lines of latitude. The size of the largest spot is about 500 kilometers across and might be high clouds illuminated by several bright lightning strokes.

APOD: May 7, 1997 - Ultraviolet Venus
Explanation: The forecast for Venus is cloudy, cloudy, cloudy. Although similar to the Earth in size and mass, Venus' slightly closer orbit to the Sun create for it a much thicker atmosphere and a much hotter surface. The thick atmosphere was photographed above in ultraviolet light in 1979 by the Pioneer Venus Orbiter. Whether or not Venus has a moon was the center of a great controversy in the 1700s and 1800s. Today we know Venus has no natural satellites. Venus's extremely uncomfortable climate was likely caused by a runaway greenhouse effect. Could Earth ever undergo runaway greenhouse heating like Venus?

APOD: December 26, 1996 - Carl Sagan 1934-1996
Explanation: Carl Sagan died last Friday at the age of 62. Sagan was the world's most famous astronomer. Among his many activities as a scientist, he contributed to the discovery that the atmosphere of Venus is prohibitively hot and dense, and found evidence that Saturn's moon Titan contains oceans stocked with the building blocks of life. Sagan was an outspoken proponent of the search for extra-terrestrial life, including sending probes to other planets and listening with large radio telescopes for signals from intelligent aliens. Sagan's outstanding ability to explain allowed almost a billion people to better understand the cosmos in which they live.

APOD: December 14, 1996 - Our Solar System from Voyager
Explanation: After taking spectacular pictures of our Solar System's outer planets, Voyager 1 looked back at six planets to take our Solar System's first family portrait. Here Venus, Earth, Jupiter, Saturn, Uranus, and Neptune, were all visible across the sky. Each, however, was now just a small speck of light, dimmer than many of the stars in the sky. Voyager 1 is only one of four human-made objects to leave our Solar System, the other three being Voyager 2, and Pioneer 10 and Pioneer 11.

APOD: September 24, 1996 - Beneath Venus' Clouds
Explanation: If the thick clouds covering Venus were removed, how would the surface appear? Using an imaging radar technique, the Magellan spacecraft was able to lift the veil from the Face of Venus and produce this spectacular high resolution imageof the planet's surface. Red, in this false-color map, represent mountains, while blue represents valleys This 3-kilometer resolution map is a composite of Magellan images compiled between 1990 and 1994. Gaps were filled in by the Earth-based Arecibo Radio Telescope. The large yellow/red area in the north is Ishtar Terra featuring Maxwell Montes, the largest mountain on Venus. The large highland regions are analogous to continents on Earth. Scientists are particularly interested in exploring the geology of Venus because of its similarity to Earth.

APOD: September 23, 1996 - Venus: Earth's Cloudy Twin
Explanation: If Venus weren't so cloudy it would be more similar to Earth. This picture by the Galileo spacecraft shows just how cloudy Venus is. Venus is very similar to Earth in size and mass - and so is sometimes referred to as Earth's sister planet - but Venus has a quite different climate. Venus' thick clouds and closeness to the Sun (only Mercury is closer) make it the hottest planet - much hotter than the Earth. Humans could not survive there, and no life of any sort has ever been found. When Venus is visible it is usually the brightest object in the sky after the Sun and the Moon. More than 20 spacecraft have visited Venus including Venera 9, which landed on the surface, and Magellan, which used radar to peer through the clouds and make a map of the surface. This visible light picture of Venus was taken by the Galileo spacecraft now in orbit around Jupiter. Many things about Venus remain unknown, including the cause of mysterious bursts of radio waves.

APOD: August 30, 1996 - Galileo Demonstrates the Telescope
Explanation: Galileo Galilei made a good discovery great. Upon hearing at age 40 that a Dutch optician had invented a glass that made distant objects appear larger, Galileo crafted his own telescope and turned it toward the sky. Galileo quickly discovered that our Moon had craters, that Jupiter had it's own moons, that the Sun has spots, and that Venus has phases like our Moon. Galileo, who lived from 1564 to 1642, made many more discoveries. Galileo claimed that his observations only made sense if all the planets revolved around the Sun, as championed by Aristarchus and Copernicus, not the Earth, as was commonly believed then. The powerful Inquisition made Galileo publicly recant this conclusion, but today we know he was correct.

APOD: June 24, 1996 - A View from Venus: Rift Valley
Explanation: Color information from the Soviet Venera landers and radar data from the Magellan spacecraft were used to construct this striking perspective view of the Venusian landscape. (In this computer generated image, the vertical scale has been exagerated.) In the foreground is the edge of a rift valley created by faulting in the crust of Venus. The valley runs all the way to the base of Gula Mons, a 2 mile high volcano seen here on the right, some 450 miles in the distance. On the left is another volcano, Sif Mons. Using radar to pierce the dense clouds continuously shrouding the Face of Venus, Magellan was able to explore over 98% of the Venusian surface, revealing a a diverse and tantalizing topography.

APOD: April 23, 1996 - Comet Hyakutake on a Starry Night
Explanation: It was a starry night in April (April 9th, 1996, 9:32 pm CDT to be exact) near Lone Jack, Missouri when Comet Hyakutake graced this astronomically rich field. Making an appearance as the brilliant evening star, Venus is overexposed at the far left. Just below Venus and slightly to the right, the Pleiades star cluster (M45) glistens. On the right hand side of the image, the comet itself shows a bright blue tail extending upwards past the nearby star cluster in the constellation Perseus (top right, the Alpha Persei Group). Hyakutake, receding from the Earth and appoaching the Sun, will sink into the western horizon at sunset in late April, disappearing from Northern Hemisphere skies.

APOD: April 18, 1996 - Hyakutake, Venus, Orion, and Pond
Explanation: Can you find Comet Hyakutake in the above picture? In this gorgeous photo, the starry night sky of April 9th is pictured with its new comet visitor. In the foreground is a pond with the lights of Kansas City, Missouri on the western horizon. On the upper left, the constellation of Orion is visible. At the center, the brightest object in the picture is the planet Venus. Venus's reflection can be seen in the pond. On the right - halfway between Venus and the photograph's edge - can be seen two bright objects fairly close to each other. Of these two, look closely at lower right object. See the tail? Comet Hyakutake is still visible for Northern observers in the Western sky and now has begun to brighten again as it nears the Sun.

APOD: March 15, 1996 - The McMath-Pierce Solar Observatory
Explanation: This odd-looking structure silhouetted in the foreground houses the three largest solar telescopes in the world. Located in Kitt Peak, Arizona, the largest telescope inside the McMath-Pierce Facility is 1.6-meters in diameter and contains only mirrors. The telescope contains no windows or lenses because focusing bright sunlight would overheat them. Visible in the background of this sunrise photo are the Moon and Venus. The telescopes are used in many research projects including determining the Sun's structure, researching the cause of the solar corona, monitoring Sun-spots and solar flares, and observing bright planets and comets near the Sun. The telescopes even help monitor the Earth's atmospheric content of ozone and CFCs!

APOD: December 14, 1995 - An Atlas Centaur Rocket Launches
Explanation: Atlas Centaur rockets have launched over 75 successful unmanned missions. These missions included the Surveyor series - the first vehicles to make soft landings on the Moon, Pioneer 10 and 11 - the first missions to fly by Jupiter and Saturn and the first man-made objects able to leave our Solar System, the Viking missions which landed on Mars, several satellites in the High Energy Astrophysics Observatory (HEAO) series, Pioneer Venus which circled and mapped the surface of Venus, and numerous Intelsat satellites. Of recent scientific interest was the Atlas launched SOHO mission which will continually observe the Sun. Atlas rockets are manufactured by Lockheed Martin Co.

APOD: November 10, 1995 - Lightning and the Space Shuttle
Explanation: There are many things about lightning that are not understood. Lightning has been seen in the atmospheres of Venus, Earth, Jupiter, and Saturn. A leading theory is that collisions of particles in clouds cause large areas of positive and negative charge. When large oppositely charged areas get close enough together, electrons and/or ions race between them and create a path where more charged particles can follow - lightning. On average, over 100 lightning strikes occur every second over the surface of the Earth. Here lightning strikes near a Space Shuttle before launch. Lightning can be extremely dangerous - stay out of open areas during thunderstorms.

APOD: September 28, 1995 - A Venusian Landscape
Explanation: This computer generated view of a Venusian volcano was created using data from NASA's Magellan spacecraft. Magellan used its onboard radar to map the surface of Venus which is hidden from telescopic observations by a perpetual cloud cover. Using this radar data to provide three dimensional information, a computer was then able to produce this view of Maat Mons, a 5 mile high volcano, from a dramatic perspective. The colors used to render the surface are based on earlier color images transmitted by TV cameras on the Soviet Venera 13 and 14 Venus landers.

APOD: September 27, 1995 - A Venus Landing
Explanation: This image is part of the first color panoramic view from Venus. It was transmitted by a TV camera on the Soviet Venera 13 lander which parachuted to the surface on March 1, 1982. Venus' clouds are composed of sulfuric acid droplets while its surface temperature is about 900 degrees Fahrenheit (482 degrees C) at an atmospheric pressure of 92 times that of sea-level on Earth. Despite these harsh conditions, the Venera 13 lander survived long enough to send back a series of images and perform an analysis of the Venusian soil. Part of the lander itself is visible in the lower right portion of the image. An earlier Soviet Venus lander, Venera 7 (1970), was the first spacecraft to return data from the surface of another planet.

APOD: August 25, 1995 - A World Explorer
Explanation: Ferdinand Magellan was a world explorer. Many consider him the greatest navigator of Europe's 16th century age of sea going exploration and credit his expedition with the first circumnavigation of planet Earth. NASA's Venus probe, the aptly named Magellan spacecraft shown above in an artist's conception, provided a global view of the poorly known surface of Venus - just as Magellan's expedition provided the beginnings of a global perspective of the Earth.

APOD: August 24, 1995 - A Radar Image of Planet Earth
Explanation: This image of Mt. Rainier, Washington USA, planet Earth, was produced by the Spaceborne Radar Laboratory which flew on the Space Shuttle Endeavour in 1994. Radar, short for RAdio Detection And Ranging, is a technique which coordinates the operation of a radio transmitter and receiver to measure the direction, strength, and timing of radio echos from the surface of distant objects. An actual image of an object can be constructed by recording and analyzing many echos. One advantage of using radar imaging in planetary studies is that images can be made regardless of cloud cover or lighting conditions. During the early 90s, NASA's Magellan spacecraft was able to use radar imaging to produce similar high resolution maps of the surface of Venus.

APOD: August 23, 1995 - A Venusian Tick
Explanation: Data from the Magellan spacecraft has shown the Face of Venus to contain a host of volcanic features. This image shows an example of a fairly common type of venusian volcanic feature. Known as a "tick" it represents a volcano about 20 miles wide at the summit with ridges and valleys radiating down its sides lending it an insect like appearance.

APOD: August 22, 1995 - Venus UnVeiled
Explanation: The surface of Venus is perpetually covered by a veil of thick clouds and remains hidden from even the powerful telescopic eyes of earth-based astronomers. However, using an imaging radar technique, the Magellan spacecraft was able to lift the veil from the Face of Venus and produce spectacular high resolution images of the planet's surface. The bright area running across the middle of this picture represents the largest highland region of Venus known as Aphrodite Terra. The large highland regions are analogous to continents on Earth. Scientists are particularly interested in exploring the geology of Venus because of its similarity to Earth. For more information about Venus and this image see the Overview of Venus.

APOD: August 19, 1995 - Our Solar System from Voyager
Explanation: After taking its spectacular pictures of the outer solar system planets, Voyager 1 looked back at six planets from the inner solar system. Here Venus, Earth, Jupiter, Saturn, Uranus, and Neptune, were all visible across the sky. Each, however, was now just a small speck of light, dimmer than many of the stars in the sky. Voyager 1 is only one of four human-made objects to leave our Solar System, the other three being Voyager 2, and Pioneer 10 and 11.

APOD: August 15, 1995 - Venus: Earth's Sister Planet
Explanation: This picture in visible light was taken by the Galileo spacecraft. Venus is very similar to Earth in size and mass - and so is sometimes referred to as Earth's sister planet - but Venus has a quite different climate. Venus' thick clouds and closeness to the Sun (only Mercury is closer) make it the hottest planet - much hotter than the Earth. Humans could not survive there, and no life of any sort has ever been found. When Venus is visible it is usually the brightest object in the sky after the Sun and the Moon. More than 20 spacecraft have visited Venus including Venera 9, which landed on the surface, and Magellan, which used radar to peer through the clouds and make a map of the surface. There are still many things about Venus's unusual atmosphere that astronomers don't understand.

APOD: August 14, 1995 - Mercury: Closest Planet to the Sun
Explanation: This picture was compiled from images taken by the NASA spacecraft Mariner 10 which flew by the planet three times in 1974. Mercury is the closest planet to the Sun, the second hottest planet (Venus gets hotter), and the second smallest planet (Pluto is smaller). Mercury rotates so slowly that one day there - "day" meaning the normal time it takes from sunset to sunset - lasts 176 days on Earth. It is difficult to see Mercury not because it is dim but because it always appears near the Sun, and is therefore only visible for a short time just after sunset or just before sunrise. Mercury is made of rocky material like Earth. No one knows why Mercury has the magnetic field that it does.