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Extrasolar Planets Encyclopaedia - http://exoplanet.eu/
Hard Copy Article
April 2004. LoPresto, Michael C., and McKay, Rachel, Detecting Our Own Solar System From Afar. The Physics Teacher, Vol 42, April 2004. DOI: 10.1119/1.1696587. pp. 208-211.
Online Articles
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2009 Feb 19. Spectacular Photo-op on Saturn. Science@NASA. Excerpt: "On Feb. 24th, there's going to be a quadruple transit of Saturn's moons," says Keith Noll of the Hubble Space Telescope Science Institute. "Titan, Mimas, Dione and Enceladus will pass directly in front of Saturn and we'll see their silhouettes crossing Saturn's cloudtops—all four at the same time."
2009 Feb 3. Alien world is slimmest and fastest known. by Govert Schilling; New Scientist. Excerpt: Astronomers have found an extrasolar planet with the smallest diameter yet measured - it is no more than twice as wide as Earth. The rocky body is also the fastest known, whipping around its star in less than a day. The planet, known as Exo-7b, lies about 390 light years away and orbits a star slightly smaller and cooler than the Sun. It was found by the French satellite COROT, which looks for the dimming caused when planets pass in front of, or transit, their parent stars. The method revealed the world's tiny size, but could not pin down its mass precisely. To do that, researchers must search for the subtle wobbles the orbiting planet induces in its host star, a difficult task since the star's own roiling activity can mask the subtle gravitational tugs of a lightweight planet. ...Malcolm Fridlund, European Space Agency project scientist for the mission, says there are "hundreds of other interesting candidate signals" in the COROT data waiting for painstaking follow-up observations with ground-based telescopes. The discovery, announced today at a COROT symposium in Paris, is good news for NASA's Kepler mission, which will hunt for Earth-like planets orbiting in the habitable zones of their stars. Kepler, which also searches for transits, is due to launch on 5 March. See also articles from:
2009 January 16. CfA Press Release No.: 2009-05. Transit Search Finds Super-Neptune. Excerpt: Cambridge, MA - Astronomers at the Harvard-Smithsonian Center for Astrophysics have discovered a planet somewhat larger and more massive than Neptune orbiting a star 120 light-years from Earth. While Neptune has a diameter 3.8 times that of Earth and a mass 17 times Earth's, the new world (named HAT-P-11b) is 4.7 times the size of Earth and has 25 Earth masses.
HAT-P-11b was discovered because it passes directly in front of (transits) its parent star, thereby blocking about 0.4 percent of the star's light. This periodic dimming was detected by a network of small, automated telescopes known as "HATNet," which is operated by the Center in Arizona and Hawaii. HAT-P-11b is the 11th extrasolar planet found by HATNet, and the smallest yet discovered by any of the several transit search projects underway around the world. ...HAT-P-11 is in the constellation Cygnus, which puts in it the field of view of NASA's upcoming Kepler spacecraft. "...we expect Kepler to measure the detailed properties of HAT-P-11 with the extraordinary precision possible only from space," said Robert Noyes, another member of the discovery team.
2008 Dec 10. Carbon Dioxide (No S.U.V.'s) Detected on Distant Planet. By KENNETH CHANG. Excerpt: Astronomers testing techniques to search for extraterrestrial life have detected carbon dioxide in the atmosphere of a planet 63 light-years away. ... The planet, HD 189733b, is far too large (about the mass of the Jupiter) and too hot (1,700 degrees Fahrenheit) for any possibility of life.
"It's really a proof of concept of using CO2 as a biomarker," said Mark R. Swain, a research scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who led the team that made the discovery. See also, NASA Press Release:
2008 Dec 9. Hubble Finds Carbon Dioxide on Extrasolar Planet - NASA's Hubble Space Telescope has discovered carbon dioxide in the atmosphere of a planet orbiting another star. This breakthrough is an important step toward finding chemical biotracers of extraterrestrial life.
2008 Dec 4. Students Find Exoplanet. by Nancy Atkinson, Universe Today. Excerpt: Three undergraduate students doing a research project discovered an extrasolar planet. The planet is about five times as massive as Jupiter, not all that big as far as previously detected exoplanets go. This is also the first planet discovered orbiting a fast-rotating hot star. The students, Meta de Hoon, Remco van der Burg, and Francis Vuijsje from Leiden University in the Netherlands, were testing a method of investigating the light fluctuations of thousands of stars in the OGLE database in an automated way. The brightness of one of the stars was found to decrease for two hours every 2.5 days by about one percent. Follow-up observations, taken with ESO's Very Large Telescope in Chile, confirmed that this phenomenon is caused by a planet passing in front of the star, blocking part of the starlight at regular intervals. ,,,The spectroscopy also showed that the star is pretty hot — almost 7000 degrees, or 1200 degrees hotter than the Sun. It is the hottest star with a planet ever discovered, and it is rotating very fast. The radial velocity method — that was used to discover most extrasolar planets known — is less efficient on stars with these characteristics. "This makes this discovery even more interesting," concludes Snellen.
2008 Nov 13. HUBBLE DIRECTLY OBSERVES A PLANET ORBITING ANOTHER STAR. RELEASE: 08-289. Excerpt: WASHINGTON -- NASA's Hubble Space Telescope has taken the first visible-light snapshot of a planet circling another star. Estimated to be no more than three times Jupiter's mass, the planet, called Fomalhaut b, orbits the bright southern star Fomalhaut, located 25 light-years away in the constellation Piscis Australis, or the "Southern Fish."...In 2004, the coronagraph in the High Resolution Camera on Hubble's Advanced Camera for Surveys produced the first-ever resolved visible-light image of the region around Fomalhaut. It clearly showed a ring of protoplanetary debris approximately 21.5 billion miles across and having a sharp inner edge. This large debris disk is similar to the Kuiper Belt, which encircles the solar system and contains a range of icy bodies from dust grains to objects the size of dwarf planets, such as Pluto.
Hubble astronomer Paul Kalas, of the University of California at Berkeley, and team members proposed in 2005 that the ring was being gravitationally modified by a planet lying between the star and the ring's inner edge.
...
Now, Hubble has actually photographed a point source of light lying 1.8 billion miles inside the ring's inner edge. The results are being reported in the November 14 issue of Science magazine.
"Our Hubble observations were incredibly demanding. Fomalhaut b is 1 billion times fainter than the star. We began this program in 2001, and our persistence finally paid off," Kalas says.
The planet is brighter than expected for an object of three Jupiter masses. One possibility is that it has a Saturn-like ring of ice and dust reflecting starlight. The ring might eventually coalesce to form moons. The ring's estimated size is comparable to the region around Jupiter and its four largest orbiting satellites. ...For more information about the Hubble Space Telescope, visit: http://www.nasa.gov/hubble
See also UC Berkeley Press Release, and HST article.
2008 Nov 13. Now in Sight: Far-Off Planets. By DENNIS OVERBYE, NY Times. Excerpt: ...Two groups of astronomers have taken the first pictures of what they say — and other astronomers agree — are most likely planets going around other stars. ...“It’s the tip of the iceberg,” said Christian Marois of the Herzberg Institute of Astrophysics in Victoria, British Columbia. ...Dr. Marois is the leader of a team that recorded three planets circling a star known as HR 8799 that is 130 light-years away in the constellation Pegasus. The other team, led by Paul Kalas of the University of California, Berkeley, found a planet orbiting the star Fomalhaut, only 25 light-years from Earth, in the constellation Piscis Austrinus. In an interview by e-mail, Dr. Kalas said that when he finally confirmed his discovery last May, “I nearly had a heart attack.” ...“I think Kepler himself would recognize these as planets orbiting a star following his laws of orbital motion,” Mark S. Marley of the Ames Research Center in Mountain View, Calif., wrote in an e-mail message elaborating on HR 8799. ...“Every extrasolar planet detected so far has been a wobble on a graph,” said Bruce Macintosh, an astrophysicist from Lawrence Livermore National Laboratory in California and a member of Dr. Marois’s team. “These are the first pictures of an entire system.”
...The three planets orbiting HR 8799 are roughly 10, 9 and 6 times the mass of Jupiter, and orbit their star in periods of 450, 180 and 100 years respectively, all counterclockwise. The Fomalhaut planet is about three times as massive as Jupiter, according to Dr. Kalas’s calculations, and is on the inner edge of a huge band of dust, taking roughly 872 years to complete a revolution of its star. Both systems appear to be scaled-up versions of our own solar system, with giant planets in the outer reaches, leaving plenty of room for smaller planets to lurk undetected in the warmer inner regions.
...Sara Seager, a planetary theorist at the Massachusetts Institute of Technology[and Kepler participating scientists], said it was significant that the planets in both cases seemed to be associated with disks of dust, particularly Fomalhaut, one of the brightest and closest stars known to be host to a massive disk. “Fomalhaut is like a Hollywood star to astronomers, so we have some personal excitement here,” Dr. Seager said. “It feels like finding out that one of your four closest friends just won the lottery big time.” Alan Boss, a planetary theorist at the Carnegie Institution of Washington [also on Kepler Science Team], said the triple-planet system in Pegasus was particularly promising, “as we expect planets to form in systems in general, whereas spurious background interlopers will generally appear as single ‘planets.’ ” But he and others cautioned that much more study of these objects was necessary and that the masses imputed to them were still highly uncertain.
...For their observations, Dr. Marois and his colleagues used the 8-meter in diameter Gemini North and the 10-meter Keck telescopes on Mauna Kea in Hawaii, both of which had been fitted with adaptive optics. Then they processed the images with a special computer program, which Dr. Marois described as “a software coronagraph,” for processing the images....
See also: Universe Today article.
2008 June 16. A Trio of Super-Earths—A harvest of low-mass exoplanets discovered with HARPS. ESO 19/08 - Science Release. Excerpt: Today, at an international conference, a team of European astronomers announced a remarkable breakthrough in the field of extra-solar planets. Using the HARPS instrument at the ESO La Silla Observatory, they have found a triple system of super-Earths around the star HD 40307. Moreover, looking at their entire sample studied with HARPS, the astronomers count a total of 45 candidate planets with a mass below 30 Earth masses and an orbital period shorter than 50 days. This implies that one solar-like star out of three harbours such planets.
2008 Apr 24. SEARCHING FOR SUPEREARTHS. By Ron Cowen, ScienceNews, Vol.173 #16. Size Mass and radius may help identify places like home. Excerpt: ST. LOUIS — In their quest to find some place just like home, astronomers are exploring a new family of planets beyond the solar system — orbs only a few times heavier than Earth. Over the past three years, researchers have discovered five superEarths, ranging from five to about 10 times the mass of the Earth. With exoplanet-seeking missions like the European Space Agency’s COROT, launched in 2006, and NASA’s Kepler, set for launch later this year, astronomers expect to find many more — and much smaller — superEarths. But because the bodies are too small and faint for state-of-the-art telescopes to image, researchers have only limited information — typically only mass and radius.
2008 Mar 14. Hubble Finds First Organic Molecule on an Exoplanet. NASA's Hubble Space Telescope has made the first detection ever of an organic molecule in the atmosphere of a Jupiter-sized planet orbiting another star. This breakthrough is an important step in eventually identifying signs of life on a planet outside our solar system. The molecule found by Hubble is methane, which under the right circumstances can play a key role in prebiotic chemistry — the chemical reactions considered necessary to form life as we know it. This illustration depicts the extrasolar planet HD 189733b with its parent star peeking above its top edge.
2008 Feb 19. Moon systems, not planets, may be place to find life. World Science - New York, NY, USA. Unlike the Earth-like breed, several suitably warm giants, dubbed “temperate Jupiters,” have been re ported found already. Such bodies can “act as ‘sign-posts’ for future studies looking for potentially habitable worlds,” said the University of Florida’s Scott Fleming, lead author of the study. ...But Fleming said this could change next year with the launch of a NASA satellite, Kepler: its instruments can detect both Earth-sized planets and moons, ...
2008 Feb 18. Worlds with potential for life might be more common than though. DailyIndia.com - Jacksonville, FL, USA. ...The next critical test for evidence that terrestrial planets could be common around stars like the sun will come next year with the launch of NASA's Kepler ...
See also:
2008 Feb 15. Smaller Version of the Solar System Is Discovered. By DENNIS OVERBYE, NY Times.
Excerpt: Astronomers said Wednesday that they had found a miniature version of our own solar system 5,000 light-years across the galaxy — the first planetary system that really looks like our own, with outer giant planets and room for smaller inner planets.
“It looks like a scale model of our solar system,” said Scott Gaudi, an assistant professor of astronomy at Ohio State University.
...In the newly discovered system, a planet about two-thirds of the mass of Jupiter and another about 90 percent of the mass of Saturn are orbiting a reddish star at about half the distances that Jupiter and Saturn circle our own Sun. The star is about half the mass of the Sun.
Neither of the two giant planets is a likely abode for life as we know it. But, Dr. Gaudi said, warm rocky planets — suitable for life — could exist undetected in the inner parts of the system.
...Since 1995, around 250 planets outside the solar system, or exoplanets, have been discovered. But few of them ... even faintly resemble our own. In many cases, giant Jupiter-like planets are whizzing around in orbits smaller than that of Mercury. But are these typical of the universe?
...The new discovery was made by a different technique ... called microlensing. If, in the ceaseless shifting of the stars, two of them should become almost perfectly aligned with Earth, the gravity of the nearer star can bend and magnify the light from the more distant one, causing it to get much brighter for a few days.
...any big planets attending the nearer star will get into the act, adding their own little boosts to the more distant starlight.
That is exactly what started happening on March 28, 2006, when a star 5,000 light-years away in the constellation Scorpius ... was picked up by the Optical Gravitational Lensing Experiment, or Ogle....
Ogle in turn immediately issued a worldwide call for continuous observations of what is now officially known as OGLE-2006-BLG-109....
Among those who provided crucial data and appeared as lead authors of the paper in Science were a pair of amateur astronomers from Auckland, New Zealand, Jennie McCormick and Grant Christie, both members of a group called the Microlensing Follow-Up Network, or MicroFUN.
...Only six planets, including the new ones, have been discovered by microlensing so far....
Alan Boss, a theorist at the Carnegie Institution of Washington [and member of the Kepler Science Working Group], said, “The fact that these are hard to detect by microlensing means there must be a good number of them — solar system analogues are not rare.”
See also:
Alien Planetary System Looks a Lot Like Home — Richard A. Kerr, Science
Planets, Resembling Earth, Raise Hopes of Extra-Terrestrial Life — eFluxMedia
2008 Feb 5. Telescope to test Antarctica's claim to 'best sky'. David Shiga, NewScientist.com news service. Excerpt: A robotic observatory installed on Dome A in Antarctica will test the site's suitability for observing and search for planets around other stars. ...The site may offer the best astronomical sky conditions in the world. Some parts of Antarctica offer ideal conditions for astronomy, devoid of clouds and boasting steady air that makes for clear viewing. Two high-altitude plateaus, called Dome A and Dome C, are especially good – but they lie deep in Antarctica's interior and are difficult to reach.
...
lugging their equipment across Antarctica with the help of six tractors ... The expedition, led by the Shanghai-based Polar Research Institute of China, installed the Plateau Observatory (PLATO), which was built at the University of New South Wales in Sydney, Australia, and incorporates instruments from China, the US, and the UK.
The observatory is automated, ...astronomers monitor its progress from other locations around the world via satellite link....
The observatory will search for planets around other stars using an array of four 14.5-centimetre telescopes called the Chinese Small Telescope Array (CSTAR).
During the uninterrupted darkness of winter near the South Pole, CSTAR will be able to monitor a 20-square-degree patch of sky – about 100 times the area of the Full Moon – for four months straight. It will look for the dimming of a star's light caused by a planet passing in front of it as seen from Earth.
..."Due to our intensive time coverage, we will be able to routinely discover extrasolar planets of the size of Neptune, and have a realistic chance of finding Earth-size planets," Wang told New Scientist.
..."For a lot of observations, a 4- or 5-metre telescope at Dome A would be as powerful as a 15-metre telescope in Chile," PLATO team member Carl Pennypacker of the University of California in Berkeley, US, told New Scientist.
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21 Dec 2007. What Alien Telescopes Would See, Looking At Earth. By John Borland, Wired Science. Excerpt: An international team of astronomers has put themselves in the shoes of alien life forms light-years away from Earth, asking whether – and how – they would be able to look at Earth through their telescopes and figure out whether our planet indeed supports life. ...The team started from the idea that Earth, as seen from that distance would appear at best as just a single pixel of light. ... over ... time, the brightness would change, as the planet rotated, and as cloud cover shifted.
... the astronomers deduced that there is enough regularity in the Earth's weather patterns (typically cloudy over rain forests, typically clear over arid regions) that smart aliens would in fact be able to puzzle out the length of our Earth day.
...they could figure out that the variations in pixel-brightness would likely be the result of fast-changing weather, very likely the result of water-based clouds.
...Not bad for studying a single pixel of light, right? The team of astronomers say they'd need a space-based telescope at least twice as large as the Hubble to do the same kind of analysis on planets circling the stars nearest to our own Sun.
NASA's Kepler telescope, planned for launch in 2009, is expected to be able to find the existence of Earth-like worlds. ...The team's paper was published this week in the online version of The Astrophysical Journal....
5 Dec 2007. Double Sunrise. A new theory proposes Earth-like planets with double the star power. By Monica Heger, ScienceLine.org. Excerpt: It’s 7 a.m. and the sun’s first rays are nudging you out of bed. ...Several hours later, another sun rises and the noontime shadows point in two directions.
That may sound like a scene from a science fiction movie, but astronomers are saying it’s not quite as far-out as it seems.
An Earth-like planet in a two-star system is a possibility, according to Nader Haghighipour and Sean Raymond, post-doctoral fellows at the University of Hawaii and the University of Colorado, respectively. They defined which parameters such a system would require to support a habitable planet in the September 1 Astrophysical Journal.
...Now, Haghighipour said, binary star systems that fit the model should be identified and searched for planets. “We don’t have to randomly look at whatever comes into our telescopes,” he added.
Their model is entirely theoretical, but if correct, expands the possibility for life outside our solar system, because binary stars are more common than single stars like our sun.
...According to Haghighipour and Raymond’s calculations, the two stars can be as close as eight astronomical units
...In an interview, Marcy said that while Haghighipour and Raymond’s study will be useful in identifying binary stars that could have planets, he would be cautious about relying on theory alone.
“History shows that we are often surprised by nature,” said Marcy.
...Determining the number of planets in multiple star systems is just one of the goals of the Kepler Mission, a NASA planet-finding mission scheduled to launch in February 2009. Kepler scientist Dave Latham is skeptical about Haghighipour’s model because it is pure theory and so specific. He is not comfortable using their model because there is not yet observational data to back it up, he said in an e-mail....
17 Nov 2007. In search of Earth's twin. By John Johnson Jr., Los Angeles Times Staff Writer. Excerpt: ...For the last 20 years, UC Berkeley astronomer Geoff Marcy has been the world's leading planet finder. Of the 260-odd planets that have been discovered in other solar systems, Marcy and his team have found 150. His most recent discovery, announced last week, is a fifth planet orbiting a star called 55 Cancri, about 41 light-years from Earth. ...The planets around 55 Cancri have a range of masses, from around 10 Earth masses at the smallest, to the largest, which is around four times as large as Jupiter. It's certainly the largest complement of planets ever found around another star.
...What are the prospects for finding planets farther out? There are three very exciting missions NASA is planning right now that would advance the search. The first one is called Kepler. It's a space-borne telescope that will be able to measure the tiniest dimming (caused by a planet crossing in front of the host star), to one part in 100,000, allowing us to detect Earth-like planets. The goal is to image a huge chunk of the sky around the constellation Cygnus, monitoring 150,000 stars continuously for four years . . . It's scheduled to launch in 2009.
...Say we find an Earth twin, what do we do then? I know exactly what we do. UC Berkeley, in conjunction with the SETI [Search for Extraterrestrial Intelligence] Institute, is building a new radio telescope north of Mt. Lassen in Hat Creek designed to search for radio and television signals from an advanced technological civilization. ...There is a written protocol ...Step A is to communicate broadly and uniformly to the world what you think you have found, so that everybody can follow up and double and triple and quadruple check your work. . . . Step Two be a . . . conference, where all of the nations are represented and we talk about it. The immediate question is what message, if any, to send back. Remember, any such dialogue will not be lively repartee, because a star 50 light-years away means it takes 50 years to get back to them and 50 years to get back to you, so the jokes will not have quite the timing that they have when Seinfeld is on stage.
9 Nov 2007. Astronomers Discover Sun's Twin at McDonald Observatory. Excerpt: FORT DAVIS, Texas - Peruvian astronomers Jorge Melendez of The Australian National University and Ivan Ramirez of The University of Texas at Austin have discovered the best "solar twin" to date, using the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory. Their findings suggest that the Sun's chemical composition is not unique, as some previously thought.
The star, HIP 56948, is more like the Sun than any yet seen, and is 200 light-years away in the constellation Draco, the dragon. The star may be a billion years older than the Sun.
Only three solar twins were previously known: 18 Scorpius, HD 98618, and HIP 100963. But while they were all like the Sun in many ways, there was one major difference: the amount of lithium they contained. They all had several times more than the Sun. Astronomers wondered if the Sun was unique in its low amount of lithium.
The discovery of this new solar twin puts that question to rest: it has the same low lithium content as the Sun. The study turned up another solar twin, HIP 73815, that contains a similarly low amount of lithium.
...The star already has been studied by the McDonald Observatory Planet Search led by University of Texas at Austin astronomer Bill Cochran. His team found that, like our Sun, HIP 56948 does not host any "hot Jupiter" planets, those massive, short-period planets orbiting close to their parent stars, so common among the more than 200 stars found to date that host one or more planets....
8 Nov 2007. Astronomers use Lick Observatory to find planet. By Lisa Fernandez, San Jose Mercury News. Excerpt: Using a telescope in the South Bay, astronomers have discovered a fifth planet circling a star beyond our solar system - a star that holds the record for the most orbiting extrasolar worlds.
The planet, discovered with help from the Shane telescope at Lick Observatory on Mount Hamilton east of San Jose, is circling 55 Cancri and located 41 light-years away, according to the National Aeronautics and Space Administration.
NASA reports the star is in the constellation Cancer and has nearly the same mass and is about the same age as the sun.
Researchers from San Francisco State University, including astronomer Debra Fischer; University of California-Berkeley astronomer Geoff Marcy and others from as far away as Hawaii discovered the fifth planet with the Doppler technique - in which a planet's gravitational tug is detected by the wobble it produces in a parent star.
"This discovery of the first quintuple planetary system has me jumping out of my socks," Marcy said. "We now know that our solar system is not unique," he said. "We strongly suspect that many of these planetary systems harbor Earth-like planets." Marcy said finding the five planets took 18 years of continuous observations at Lick.
The newly discovered planet - the fourth from its star - is about 45 times the mass of the Earth and may be similar to Saturn in its composition and appearance. ...."It is amazing to see our ability to detect extrasolar planets growing," said Alan Stern, associate administrator for the Science Mission Directorate at NASA headquarters in Washington, D.C., in a statement. "We are finding solar systems with a richness of planets and a variety of planetary types comparable to our own."
See also 7 Nov 2007 PBS News Hour podcast, and article,
Astronomers Spy New Planet in Distant Solar System. PBS News Hour.
7 Nov 2007. Could this be Earth's near twin? Introducing planet 55 Cancri f. The Guardian.
7 Nov 2007. Planet discovery excites scientists. Huntsville Times.
7 Nov 2007. Discovery raises hope of finding habitable planet. Denver Post.
7 Nov 2007. Astronomers find giant gas planet orbiting star's 'habitable zone'. San Francisco Chronicle.
6 Nov, 2007. Scientists discover record-breaking fifth planet orbiting a star beyond our solar system. UC Santa Cruz press release.
6 Nov 2007. A New Earth. The Guardian.
6 Nov 2007. Scientists Discover Record Fifth Planet Orbiting Nearby Star. Excerpt: PASADENA, Calif. - Astronomers have announced the discovery of a fifth planet circling 55 Cancri, a star beyond our solar system. The star now holds the record for number of confirmed extrasolar planets orbiting in a planetary system. 5 Cancri is located 41 light-years away in the constellation Cancer and has nearly the same mass and age as our sun. It is easily visible with binoculars. Researchers discovered the fifth planet using the Doppler technique, in which a planet's gravitational tug is detected by the wobble it produces in the parent star. NASA and the National Science Foundation funded the research. ...Debra Fischer ...and University of California, Berkeley, astronomer Geoff Marcy, plus a team of collaborators discovered this planet....
19 Oct 2007. Do super-Earths have geology suited to life? Debate erupts over whether alien planets have active plate tectonics. Eric Hand, Nature News.
Excerpt: Do giant Earth-like planets have continents and mountains? The discovery in recent years of a handful of rocky planets orbiting stars outside the Solar System has scientists wondering whether those planets are as suitable as Earth for life. This month, two research groups have entered the debate by butting heads over whether active plate tectonics are likely on such planets.
The movement of tectonic plates, which on our own planet created the Himalayas and moved the continents to their current positions, is thought to be important for moderating a planet’s temperature and recycling materials that may nourish life. ...Diana Valencia, leading a group of scientists at Harvard University in Cambridge, Massachusetts, says that tectonic plates are inevitible as rocky planets get bigger. As size increases, so does the amount of heat flowing up from the planet’s radioactive core through the gooey mantle. This strikes the planet’s crusty lid with increasing force, eventually breaking it into plates. ...But Earth might be an anomaly, and the trend might not extend to bigger rocky planets says Craig O’Neill, a planetary scientist at Macquarie University in Sydney, Australia. O’Neill and his group have come to the exact opposite conclusion to Valencia. Their model, published in Geophysical Research Letters 2, shows that as a planet gets bigger, the increasing force of gravity squeezes crustal rocks together into a solid lid, making it more difficult for forces from below to crack it into plates....
13 Oct 2007. The Planetary Horizon. Astrobiology Magazine. A newly published review outlines the prospects of finding Earth-like, habitable planets around distant stars using current planet-hunting techniques.
October 02, 2007. How Do Artists Portray Exoplanets They've Never Seen? By JR Minkel, ScientificAmerican.com. Excerpt: How realistic are images of planets around other stars—and should they be? CLICK HERE FOR AN IMAGE GALLERY
Stargazers have yet to lay eyes on any of the nearly 240 planets detected outside our solar system. These so-called exoplanets are too faint for current telescopes to distinguish from the stars they orbit... Yet popular news accounts, supplied by space agency press services, overflow with bold, almost photo-realistic images of distant worlds.
Naturally, people can get confused. When San Francisco artist Lynette Cook painted a particularly striking image of a newly discovered planet passing in front of the star HD 209458 for a 1999 NASA press release, she received e-mail asking what kind of amazing image processing software she had used. "A lot of people didn't understand that it was a rendering," she says.
When astronomers make a sexy new discovery that doesn't lend itself easily to visual inspection, they turn to artists like Cook to bring it to life. A compelling image has the power to transform even the most complex data into an easy-to-grasp mental snapshot, but it runs the risk of fooling people into believing an iffy scientific case is closed.
...a planet as hefty as the solar gas giants Saturn (95 Earth masses) or Jupiter (318) would almost certainly be gaseous. Smaller planets of up to a few dozen Earth masses might range from those made mostly of rock and ice to larger ones with a solid core enshrouded by a mixture of thick gas.
Orbital distance would also influence a planet's color, says astronomer Geoffrey Marcy of the University of California, Berkeley, whose team has discovered 145 of the known exoplanets.
Jupiter and Saturn have brownish-orangey tints because their atmospheres swirl with carbon-based molecules that reflect light of those colors, Marcy says; a hotter atmosphere would evaporate water clouds and break down those molecules into carbon dioxide and methane, which scatter blue light. The effect might result in "deep blue billiard balls," he says....
25 Sep 2007. NASA locating Star Wars planets - for real. Scott Casey | Excerpt:
It's a long way from the wooded, desert or icy realms of the fictional planets of Star Wars but NASA scientists believe equally strange worlds made purely out of water, iron or even carbon are all possible. Scientists from a variety of US universities and the NASA Goddard Space Flight Centre have compiled a list of 14 different types of planets that are similar in size to our planet but vastly different in their composition. "We're thinking seriously about the different kinds of roughly Earth-size planets that might be out there - like George Lucas, but for real," NASA scientist Marc Kuchner said in a release. Some of the planets are pure water ice, carbon, iron, silicate, carbon monoxide, and silicon carbide; others are mixtures of these various compounds. The scientists did not simply assume other solar systems' planets would resemble our own but took data on the composition of protoplanetary disks, the birthplace of planets, and worked out what planets could develop. "We have learned that extrasolar giant planets often differ tremendously from the worlds in our solar system, so we let our imaginations run wild and tried to cover all the bases with our models of smaller planets," Mr Kuchner said. "We can make educated guesses about where these different kinds of planets might be found. For example, carbon planets and carbon-monoxide planets might favour evolved stars such as white dwarfs and pulsars.
...
"The scientists look forward to applying their data when results come back from missions such as the French Corot satellite, launched on December 27, 2006, and NASA's Kepler spacecraft, scheduled to launch in 2009, that can find planets not much larger than Earth.
...The transits yield the planets size, and follow-up studies can measure the mass. By comparing a planet's size and mass, astronomers might be able to determine whether it is mostly water ice or mostly iron, for example. A paper on the research is currently scheduled to appear in the October 20 issue of the Astrophysical Journal.
03 May 2007. European planet hunters on brink of Earth-sized prize. NewScientist.com news service. Excerpt: EUROPEAN planet hunters are stealing a march on their American rivals. After last week's discovery of a "habitable" extrasolar planet the mass of five Earths - the smallest yet found - European astronomers have had more good news. Their new space telescope, called COROT, is proving 10 times as sensitive as expected. The spacecraft seems sharp enough to detect planets as small as Earth, a task widely thought impossible in advance of the launch of NASA's Kepler telescope in October 2008. ...
"The big news is that by doing this we got our first estimates of the instrument's capability," says Fridlund. And the news is very good. ... By the time the team has created the software to enable these final refinements in data, Fridlund says COROT may be performing up to 30 times better than its design specification. ...The team, which includes astronomers from Europe and Brazil, is hurrying to develop new software to process raw COROT data automatically. If they are successful, the telescope could bag its first Earth-sized world later this year.
25 April 2007. Earth-like planet found around star Gliese 581, 20.5 LYs away. By William Atkins; IT Wire. Excerpt: European astronomers have discovered a planet orbiting a red dwarf star called Gliese 581. They state that the planet—called Gliese 581 c—could contain water, and if it does, it would be in a liquid state. The team includes Stephane Udry, of the Geneva Observatory in Switzerland, and Xavier Delfosse, of the Grenoble University in France. They used the HARPS (High Accuracy Radial velocity Planet Searchers) instrument on the European Southern Observatory (La Silla, Chile) to discover the planet.
The planet is about 1.5 times larger than the Earth and has about five times more mass than the Earth. Also, it is the first exoplanet (or extrasolar planet: a planet outside of the solar system) to be discovered that orbits its star within what is considered a habitable zone for the existence of liquid water. The team thinks that the planet’s surface temperature is between 0 and 40 degrees Celsius (32 and 104 degrees Fahrenheit).... Additional information is contained at Space.com: http://www.space.com/scienceastronomy/070424_hab_exoplanet.html. [See also ESO press release, and Phil Plait's Bad Astronomy site, as well as article Out of our world: Earth-like planet, By Dan Vergano, USA TODAY 4/24/2007]
10 April 2007. Space mission could detect hundreds of exiled planets. David Shiga,
NewScientist.com news service. Excerpt: A proposed space mission [the Microlensing Planet Finder] could find hundreds of free-floating, Earth-size planets that were ejected from their solar systems in primordial tussles with their siblings. Based on a technique called microlensing, the mission could also find many planets orbiting their parent stars at the right distance to support life. ...Led by David Bennett of the University of Notre Dame ...The mission would place a telescope with a 1.1-metre mirror in orbit around Earth. It would monitor about 100 million stars in the galactic bulge, the dense concentration of stars towards the galaxy's centre. It would be able to detect planets with just one-tenth the mass of Earth, with orbits slightly wider than that of Mercury's around the Sun. ...During the four-year mission, it could turn up about 150 planets about as massive as Earth, if these are common around other stars, and an estimated 5000 or so Jupiter-mass planets, Bennett says. "We could discover analogues of all the planets in our solar system except for Mercury," Bennett told New Scientist. A planet like Mercury would be too lightweight and too close to its parent star to be discernible in the microlensing event . The microlensing mission could also detect planets not bound to any star. Many planets could get ejected early on in developing solar systems because of the gravitational influence of other planets, Bennett says.
...NASA already has one mission in the works that could detect Earth-like planets. Called Kepler, it is set to launch in late 2008, and will watch for the dimming of stars as planets pass in front of them. ...Kepler team member David Latham of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, US, says microlensing can provide a more thorough census of planets around other stars, especially for very low-mass planets. "I think it's something that is well worth doing," he told New Scientist. But he points out that planets detected by Kepler can be observed repeatedly, and with different telescopes, potentially allowing details such as their atmospheric composition and weather to be discerned. "That's not something you can do with the microlensing planets," he says, since the events rely on the chance alignment of two stars as one passes in front of the other....
21 Mar 2007. Planetfinder: An Online Interactive Module for Learning How Astronomers Detect Extrasolar Planets. by Richard McCray, University of Colorado. The Astronomy Education Review, Issue 2, Volume 5, 2006-2007. Abstract: Planetfinder is a Web-based module designed to enable undergraduates to learn how astronomers detect extrasolar planets through observations of the Doppler shifts of a star's spectral lines. The module guides students through the process of measuring the masses and orbital parameters of actual extrasolar planets by fitting model Doppler curves to the data. The main goal of the exercise is to give students an understanding of the process of scientific measurement and model fitting. The exercise can be done at various levels of difficulty, ranging from measuring the properties of planetary systems having nearly circular orbits without using algebra, to exploring properties of systems having eccentric orbits and the associated equations of motion. The module is self-checking. Student work is stored in a database that is easily accessible by the instructor. The module has been tested at several institutions and is available for public use.
21 Feb 2007. NASA'S Spitzer First to Crack Open Light of Faraway Worlds. NASA's Spitzer Space Telescope has captured for the first time enough light from planets outside our solar system, known as exoplanets, to identify signatures of molecules in their atmospheres.
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October 2006. The Planet Hunters. By Robert Irion. Smithsonian Magazine. Excerpt: Nevermind the demotion of Pluto to a dwarf planet. Astronomers have found about 200 planets orbiting other stars, and they say it's only a matter of time before they discover another Earth. ...Greg Laughlin predicts the satellites will find such bodies in droves, even around stars where no large planets have yet been seen. "It's very likely that [sun-like] stars are accompanied by terrestrial planets," he says. "My intuitive sense is that our solar system is not uncommon at all." Berkeley's Geoff Marcy agrees, because he says every star is born with enough raw material around it to create many planets. ..."Maybe Jupiters are rare," he says, "but rocky planets almost certainly are common. I just don't see how making an Earth could be hard." ... The most surprising feature of exoplanets so far, Marcy says one day in his office on the Berkeley campus, is their unusual orbits. In the classic "overhead view" diagram of our solar system, the planets (except for oddball Pluto, recently demoted to a dwarf planet) trace nifty concentric circles around the sun. Marcy reaches behind his neat desk and takes out an orrery, a mechanical model of our solar system. Metal balls at the ends of spindly arms swivel around the sun. "We all expected to see these phonograph-groove circular orbits," Marcy says. "That's what the textbooks said about planetary systems. So when we first started seeing eccentric orbits in 1996, people said they can't be planets. But they turned out to be a harbinger of things to come."....
5 Oct 2006. Extrasolar planets discovered. inthenews.co.uk - Excerpt: 16 ultra-short-period planets have been detected by ... in our galaxy by Nasa's Hubble telescope. ...[They] are orbiting a variety of distant stars in the central region of the Milky Way and were discovered as part of Hubble's deepest search into the galaxy. ...Five of the newly-discovered planets are unlike any others found in nearby searches. Known as ultra-short-period planets (USPPs), they orbit their stars in less than one Earth day. The USPP with the shortest orbit, Sweeps-10, whirls around its star in just ten hours and is among the hottest planets ever discovered. ...The findings provide a sounds basis for a study that it is to be carried out from 2008 by Nasa's Kepler mission, which will monitor a region of the Milky Way to detect planets around distant stars.
Oct. 4, 2006. Hubble Finds Extrasolar Planets Far Across Galaxy. RELEASE: 06-326 - NASA's Hubble Space Telescope has discovered 16 extrasolar planet candidates orbiting a variety of distant stars in the central region of our Milky Way galaxy. The planet bonanza was uncovered during a Hubble survey called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). ...Hubble peered at ...stars in the crowded central bulge of our galaxy 26,000 light-years away. ...The term "window" implies a clear view into the galactic center, but much of the galactic plane is obscured by dust. Hubble monitored 180,000 stars for periodic, brief dimming in a star's brightness ...over a continuous seven-day period Feb. 23-29, 2004. To ensure the dimming was caused by an object orbiting a star, the team used Hubble to detect from two to 15 consecutive transits for each of the16 planet candidates. Two stars in the field are bright enough that the SWEEPS team could make an independent confirmation of a planet's presence by spectroscopically measuring a slight wobble in the star's motion due to the gravitational pull of an unseen companion. They used the European Southern Observatory's Very Large Telescope, located on Mount Paranal in Chile, to measure a slight wobble in the star. ...The Hubble SWEEPS program is an important proof-of-concept for NASA's future Kepler Mission, scheduled for launch in 2008. The Kepler observatory will continuously monitor a region of the Milky Way galaxy to detect transiting planets around mostly distant stars. Kepler will be sensitive enough to detect possibly hundreds of Earth-size planet candidates in or near the habitable zone, the distance from a star where liquid water could feasibly exist on a planet's surface.
July 2, 2006. Physics Today - Letters - NASA's mission of space exploration:Some fine points. [Re: Roger Blandford's Reference Frame titled "Exploring the Universe" (PHYSICS TODAY, April 2005, page 10)] Excerpt: ... some astronomers worry that "programs with a connection to life will be favored over fundamental investigations in the inanimate, physical sciences." The president's vision explicitly calls for NASA to "conduct advanced telescope searches for Earth-like planets and habitable environments around other stars"[1] ... ...Blandford draws the incorrect conclusion that the more than 160 current extrasolar planet candidates[2] imply that our solar system is unrepresentative and hence that the search for habitable planets may be extraordinarily difficult.
... scientists have no reason to believe that planetary systems similar to our own are not commonplace. The 160 known extrasolar planetary systems were nearly all discovered by Doppler spectroscopy and photometric transits, methods that strongly favor the detection of gas-giant planets with short-period orbits. Such planets are indeed likely to prevent the formation and stability of habitable, Earth-like planets, but they orbit only about 10% of nearby Sun-like stars. For the remaining 90% or so of such stars, the planetary census takers have not been collecting high-precision data long enough to detect Jupiter-like planets on the 12-year-period orbits that would herald the presence of exact solar-system analogues. In fact, the recent discovery of more than half a dozen super-Earths, planets in the range of 5 to 15 Earth masses, implies that Earth-mass planets are commonplace. NASA's Kepler mission, slated for launch around 2008, will determine the frequency of Earth-like planets through an exhaustive transit survey of 100 000 stars.[3]
References
1.See The Vision for Space Exploration, Feb 2004.
2.See the International Astronomical Union's Working Group on Extrasolar Planets website
3.See Kepler Mission website.
Alan Boss
(boss{at}dtm.ciw.edu)
Carnegie Institution
Washington, DC
....
May 18, 2006. Planet Group Similar to Solar System Is Found. By DENNIS OVERBYE. NY Times. Excerpt: A team of European astronomers said yesterday that they had found one of the closest analogues yet to our solar system: three planets and an asteroid belt circling a pale Sun-like star about 42 light-years away in the constellation Puppis. The two innermost of the new Puppis planets, each about 10 times the mass of Earth, are probably rocky like our own home, but they circle too tightly about their star to be habitable. The third planet, about 18 times the mass of Earth, circles at a distance of about 60 million miles, within the star's so-called habitable zone, where the temperatures would allow the existence of liquid water, the authors said. The planet is still too big to be considered Earth-like, and is probably shrouded in hydrogen like Neptune or Uranus, and so is an unlikely environment for life. ...In a commentary accompanying the Nature paper, Prof. David Charbonneau of Harvard said it was a mystery how HD 69830 could have such a massive disk of debris around it while the star itself, according to the observations, has a lower abundance of heavy elements, the stuff of planets. Dr. Charbonneau said the results were encouraging to those who hope to someday find Earth-like planets in habitable zones around other stars. ...
See also Astronomers in Switzerland find new 3-planet solar system by David Perlman, San Francisco Chronicle Science Editor.
17 May 2006 Ron Bissinger, who is on the Kepler Mission EPO advisory board, co-authored a technical paper in the Astrophysical Journal entitled A Transiting Planet of a Sunlike Star.
17 May 2006. Distant 'Earths' will only be seen from space - NewScientist.com news service. Kimm Groshong. Excerpt: In the hunt for planets orbiting distant stars, astronomers are continuing to push ground-based technology, hoping to provide existing and future space telescopes with lists of promising targets. About 170 extrasolar planets have been found so far, but direct detection remains extremely difficult. Isolating light reflected towards the Earth from the exoplanet itself would give astronomers valuable information about what that world was like. Now, a European team led by Alessandro Berton at the Max Planck Institute of Astronomy in Heidelberg, Germany has simulated highly complex Earth-based telescope configurations to see how useful they might be in the hunt. ...Berton notes that space-based missions like Kepler and Darwin – scheduled for launch in 2008 and 2015, respectively – are bound to gather better results than ground-based telescopes without atmospheric interferences.
2006 Mar 3. Planets of Binary Star Systems. by John G. Cramer, Alternate View Column AV-133, Analog Science Fiction & Fact Magazine July-Aug 2006 issue. Excerpt: An astronomer once told me that Nature really hates to solve the Three-Body Problem, as evidenced by the fact that She avoids it whenever She can. He was referring to the large number of binary star systems in the universe (two stars in relatively close orbits), and the relative rarity of triple-star systems (three stars with relatively small mutual separations). ...The algebraic difficulties of the three-body problem are not a major impediment to the study of planetary orbits ...with modern computers we can calculate orbits of multi-body systems to whatever precision we are willing to expend the resources to obtain. However, ... we find that most of the orbits for close three-body systems are unstable. After a few orbits, one of the bodies is often ejected from the system, leaving behind a simpler two-body system. ...The intrinsic instability and chaos of most close three-body orbits raises the question of whether binary star systems can be expected to have planets at all, and in particular, to have Earth-like planets in stable orbits around them.
...
On the observational front, recent successes in astronomical searches for planets orbiting stars outside our solar system have found a number of examples of Jupiter-like gas giant planets orbiting in binary star systems with separation distances ranging from about 12 to 1000 AU. On the theoretical front, Dr. Alan G. Boss of the Carnegie Institution in Washington , DC , has developed a numerical model of the proto-planetary gas cloud in a binary star system, which removes the artificial viscosity effects of previous models, but includes vertical motion in the disk and convective cooling. His calculations indicate that planet formation may actually be enhanced in a binary star system.
Boss found that... gas-giant planets can emerge in the planet-forming disk of gas and dust in the same way they do around single stars. Ice grains can combine through the process of core accretion and grow into solid cores of several Earth-mass sizes.
But in addition to core accretion, there is another planet forming mechanism that may be even more important in binary systems. The disc of gas and dust orbiting a new star, if it is massive enough, is intrinsically unstable to gravitational attraction because once a region of higher-than-average density appears, it tends to grow progressively larger. Boss has shown that in cases where a proto-planetary disc around one of the stars is just massive enough to be on the edge of such an instability, the passage of the binary companion, with a time scale of around 1000 years, can act as a trigger to precipitate planet formation. ...On the basis of Boss’ calculations, there seems to be a distinct difference between the processes of planet formation in single star systems and binary systems, with the latter actually “pumped” toward planet formation earlier and perhaps with different location probabilities.
The implications of this work for SF are fairly clear, and it vindicates the work of many SF authors. Writers should have no reservations about placing Earth-like planets around binary star systems, or having scenes with two “suns” in the sky, etc.
Reference: Planet Formation in Binary Systems: “Gas Giant Protoplanets Formed by Disk Instability in Binary Star Systems”, Alan G. Boss [on Kepler Science Team], Astrophysics Journal 641 20 (2006); ArXiv preprint astro-ph/0512477.
25 January 2006. Release Number: STScI-2006-06 Astronomers Find Smallest Extrasolar Planet Yet Around Normal Star. Excerpt: Using an armada of telescopes, an international team of astronomers has found the smallest planet ever detected around a normal star outside our solar system... five times as massive as Earth and orbits a red dwarf, a relatively cool star, every 10 years. The distance between the planet, designated OGLE-2005-BLG-390Lb, and its host is about three times greater than that between the Earth and the Sun. ... "This finding means that Earth-mass planets are not that uncommon," said Kailash Sahu of the Space Telescope Science Institute in Baltimore, Md., and a founding member of the Probing Lensing Anomalies Network team (PLANET) that helped detect the new planet. "If we found one, there must be more."...Astronomers discovered the planet indirectly with a technique called gravitational microlensing. The technique takes advantage of the random motions of stars, which are generally too small to be noticed. If one star, however, passes precisely in front of another star, the gravity of the foreground ("lens") star bends the light from the background ("source") star. The foreground star, therefore, acts like a giant lens, amplifying the light from the background star, a phenomenon called gravitational microlensing. A planetary companion around the foreground star can produce additional brightening of the background star. This additional brightening can thus reveal the planet, which is otherwise too faint to be seen by telescopes. ...In the past decade, the OGLE team has found more than 1,000 microlensing events. OGLE's monitoring team, however, may not notice the short-duration brightening caused by a planet. PLANET has a dedicated army of 1-meter class telescopes, including the European Space Observatory's Danish 1.54-meter telescope at La Silla in Chile, to specifically look for planetary signatures through continuous monitoring of ongoing microlensing events. See also article in Oakland Tribune, which also has reference to Kepler Mission.
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NEW NAV MATH PRODUCT IS OUT OF THIS WORLD. Navigator's Rich Alvidrez is the mastermind behind "The Mathematics of Rotating Objects," an Educational product focusing on Extra-Solar Planets for teachers in grades 5 - 12. The product, available for download on the PlanetQuest website, enables classroom teachers to have a contextual learning tool for graphical representation of data. This product is designed to introduce periodic functions in an interesting and authentic fashion. For more information, contact Rich Alvidrez at Richard.F.Alvidrez@jpl.nasa.gov
Dates unknown:
"Seeing Sharper" with Rolf and Ray: Interferometry in Astronomy Magazine
Sky & Telescope Feature on Interferometry: Optical Interferometry Comes of Age
It's a Natural! PlanetQuest Website Profiled In Natural History Magazine
Terrestrial Planet Finder Lands on Aviation Week Cover
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