Astronomy Picture of the Day Search Results for "Arp"

APOD: 2008 November 15 - Arp 273
Explanation: The two prominent stars in the foreground of this colorful skyscape are well within our own Milky Way Galaxy. Their spiky appearance is due to diffraction in the astronomer's telescope. But the two eye-catching galaxies in view lie far beyond the Milky Way, at a distance of about 200 million light-years. Their distorted appearance is due to gravitational tides as the pair engage in close encounters. From our perspective, the bright cores of the galaxies are separated by about 80,000 light-years. Cataloged as Arp 273 (also as UGC 1810), the galaxies do look peculiar, but interacting galaxies are now understood to be common in the universe. In fact, the nearby large spiral Andromeda Galaxy is known to be some 2 million light-years away and approaching the Milky Way. Arp 273 may offer an analog of their far future encounter. Repeated galaxy encounters on a cosmic timescale can ultimately result in a merger into a single galaxy of stars.

APOD: 2008 November 4 - The Double Ring Galaxies of Arp 147 from Hubble
Explanation: How could a galaxy become shaped like a ring? Even more strange: how could two? The rim of the blue galaxy pictured on the right shows an immense ring-like structure 30,000 light years in diameter composed of newly formed, extremely bright, massive stars. This blue galaxy is part of the interacting galaxy system known as Arp 147, and shows a ring because it has recently collided with the other galaxy in the frame, the red galaxy on the left. Unusually, even this red galaxy shows a ring like band, although it is seen nearly edge-on. When galaxies collide, they pass through each other -- their individual stars rarely come into contact. Clouds of interstellar gas and dust become condensed, causing a wave of star formation to move out from the impact point like a ripple across the surface of a pond. The above image was taken last week by NASA's Hubble Space Telescope to demonstrate the ability of its Wide Field Planetary Camera 2 after some recent technical difficulties.

APOD: 2008 July 31 - Galaxies on a String
Explanation: Galaxies NGC 5216 (top right) and NGC 5218 really do look like they are connected by a string. Of course, that string is a cosmic trail of gas, dust, and stars about 22,000 light-years long. Also known as Keenan's system (for its discoverer) and Arp 104, the interacting galaxy pair is some 17 million light-years away in the constellation Ursa Major. The debris trail that joins them, along with NGC 5218's comma-shaped extension and the distorted arms of NGC 5216 are a consequence of mutual gravitational tides that disrupt the galaxies as they repeatedly swing close to one another. Drawn out over billions of years, the encounters will likely result in their merger into a single galaxy of stars. Such spectacular galactic mergers are now understood to be a normal part of the evolution of galaxies, including our own Milky Way.

APOD: 2008 July 21 - The Colliding Spiral Galaxies of Arp 271
Explanation: What will become of these galaxies? Spiral galaxies NGC 5426 and NGC 5427 are passing dangerously close to each other, but each is likely to survive this collision. Most frequently when galaxies collide, a large galaxy eats a much smaller galaxy. In this case, however, the two galaxies are quite similar, each being a sprawling spiral with expansive arms and a compact core. As the galaxies advance over the next tens of millions of years, their component stars are unlikely to collide, although new stars will form in the bunching of gas caused by gravitational tides. Close inspection of the above image taken by the 8-meter Gemini-South Telescope in Chile shows a bridge of material momentarily connecting the two giants. Known collectively as Arp 271, the interacting pair spans about 130,000 light years and lies about 90 million light-years away toward the constellation of Virgo. Quite possibly, our Milky Way Galaxy will undergo a similar collision with the neighboring Andromeda Galaxy in about five billion years.

APOD: 2008 April 30 - Arp 272
Explanation: Linking spiral arms, two large colliding galaxies are featured in this Hubble Space Telescope view, part of a series of cosmic snapshots released to celebrate the Hubble's 18th anniversary. Recorded in astronomer Halton Arp's Atlas of Peculiar Galaxies as Arp 272, the pair is otherwise known as NGC 6050 and IC 1179. They lie some 450 million light-years away in the Hercules Galaxy Cluster. At that estimated distance, the picture spans over 150 thousand light-years. Although this scenario does look peculiar, galaxy collisions and their eventual mergers are now understood to be common, with Arp 272 representing a stage in this inevitable process. In fact, the nearby large spiral Andromeda Galaxy is known to be approaching our own galaxy and Arp 272 may offer a glimpse of the far future collision between Andromeda and the Milky Way.

APOD: 2007 November 1 - Peculiar Arp 87
Explanation: A cosmic bridge of stars, gas, and dust stretches for over 75,000 light-years and joins this peculiar pair of galaxies cataloged as Arp 87. The bridge is strong evidence that these two immense star systems have passed close to each other and experienced violent tides induced by mutual gravity. As further evidence, the face-on spiral galaxy on the right, also known as NGC 3808A, exhibits many young blue star clusters produced in a burst of star formation. The twisted edge-on spiral on the left (NGC 3808B) seems to be wrapped in the material bridging the galaxies and surrounded by a curious polar ring. While such interactions are drawn out over billions of years, repeated close passages should ultimately result in the merger of this pair of galaxies into a larger single galaxy of stars. Although this scenario does look peculiar, galactic mergers are thought to be common, with Arp 87 representing a stage in this inevitable process. The Arp 87 pair are about 300 million light-years distant toward the constellation Leo. The prominent edge-on spiral at the far left appears to be a more distant background galaxy and not involved in the on-going merger.

APOD: 2007 February 16 - Polar Ring Galaxy NGC 2685
Explanation: NGC 2685 is a confirmed polar ring galaxy - a rare type of galaxy with stars, gas and dust orbiting in rings perpendicular to the plane of a flat galactic disk. The bizarre configuration could be caused by the chance capture of material from another galaxy by a disk galaxy, with the captured debris strung out in a rotating ring. Still, observed properties of NGC 2685 suggest that the rotating ring structure is remarkably old and stable. In this fascinating view of the peculiar system also known as Arp 336 or the Helix galaxy, the strange, perpendicular rings are easy to trace as they pass in front of the galactic disk, along with other disturbed outer structures. NGC 2685 is about 50,000 light-years across and 40 million light-years away in the constellation Ursa Major.

APOD: 2006 December 1 - In the Arms of NGC 1097
Explanation: A smaller companion seems wrapped in the spiral arms of enigmatic galaxy NGC 1097. This amazingly deep image of the peculiar spiral system, also known as Arp 77, actually combines data from two telescopes, one in the northern and one in the southern hemisphere of planet Earth. The faint details revealed include hints of a mysterious jet emerging toward the top of the view. Seen to be about 42,000 light-years from the larger galaxy's center, the companion galaxy is gravitationally interacting with the spiral and will ultimately merge with it. NGC 1097's center also harbors a massive black hole. NGC 1097 is located about 45 million light-years away in the chemical constellation Fornax.

APOD: 2006 January 8 - Arp 188 and the Tadpoles Tidal Tail
Explanation: In this stunning vista recorded with the Hubble Space Telescope's Advanced Camera for Surveys, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation Draco. Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from left to right in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper left. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.

APOD: 2005 November 22 - A Galactic Collision in Cluster Abell 1185
Explanation: What is a guitar doing in a cluster of galaxies? Colliding. Clusters of galaxies are sometimes packed so tight that the galaxies that compose them collide. A prominent example occurs on the left of the above image of the rich cluster of galaxies Abell 1185. There at least two galaxies, cataloged as Arp 105 and dubbed The Guitar for their familiar appearance, are pulling each other apart gravitationally. Most of Abell 1185's hundreds of galaxies are elliptical galaxies, although spiral, lenticular, and irregular galaxies are all clearly evident. Many of the spots on the above image are fully galaxies themselves containing billions of stars, but some spots are foreground stars in our own Milky Way Galaxy. Recent observations of Abell 1185 have found unusual globular clusters of stars that appear to belong only to the galaxy cluster and not to any individual galaxy. Abell 1185 spans about one million light years and lies 400 million light years distant.

APOD: 2005 October 8 - Peculiar Arp 295
Explanation: A spectacular bridge of stars and gas stretches for nearly 250,000 light-years and joins this famous peculiar pair of galaxies cataloged as Arp 295. The cosmic bridge between the galaxies and the long tail extending below and right of picture center are strong evidence that these two immense star systems have passed close to each other in the past, allowing violent tides induced by mutual gravity to create the eye-catching plumes of stellar material. While such interactions are drawn out over billions of years, repeated close passages should ultimately result in the merger of this pair of galaxies into a larger single galaxy of stars. Although this scenario does look peculiar, galactic mergers are thought to be common, with Arp 295 representing an early stage of this inevitable process. The Arp 295 pair are the largest of a loose grouping of galaxies about 270 million light-years distant toward the constellation Aquarius. This deep color image of the region was recorded in September 2003 using the USNO 1 meter telescope near Flagstaff, Arizona.

APOD: 2005 September 12 - The Colliding Galaxies of NGC 520
Explanation: Is this one galaxy or two? The jumble of stars, gas, and dust that is NGC 520 is now thought to incorporate the remains of two separate galaxies. A combination of observations and simulations indicate the NGC 520 is actually the collision of two disk galaxies. Interesting features of NGC 520 include an unfamiliar looking tail of stars at the image bottom and a perhaps more familiar looking band of dust running diagonally across the image center. A similar looking collision might be expected were our disk Milky Way Galaxy to collide with our large galactic neighbor Andromeda (M31). The collision that defines NGC 520 started about 300 million years ago and continues today. Although the speeds of stars are fast, the distances are so vast that the interacting pair will surely not change its shape noticeably during our lifetimes. NGC 520, at visual magnitude 12, has been noted to be one of the brightest interacting galaxies on the sky, after interacting pairs of galaxies known as the Antennae. NGC 520 was imaged above in spectacular fashion by the Gemini Observatory in Hawaii, USA. Also known as Arp 157, NGC 520 lies about 100 million light years distant, spans about 100 thousand light years, and can be seen with a small telescope toward the constellation of the Fish (Pisces).

APOD: 2004 May 15 - Arp 188 and the Tadpole's Tidal Tail
Explanation: In this stunning vista recorded with the Hubble Space Telescope's Advanced Camera for Surveys, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation Draco. Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from left to right in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper left. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.

APOD: 2003 December 11 - Arp 81: 100 Million Years Later
Explanation: From planet Earth, we view this strongly interacting pair of galaxies, cataloged as Arp 81, as they were only about 100 million years after their mutual closest approach. The havoc wreaked by gravity during their ominous encounter is detailed in this color composite image from the Hubble Space Telescope, showing twisted streams of gas and dust, a chaos of massive star formation, and a tidal tail stretching for 200 thousand light-years or so as it sweeps behind the cosmic wreckage. Also known as NGC 6622 (left) and NGC 6621, the galaxies are roughly equal in size but are destined to merge into one large galaxy in the distant future, making repeated approaches until they finally coalesce. Located in the constellation Draco, the galaxies are 280 million light-years away. The dark vertical band which seems to run through NGC 6621's location is a camera artifact.

APOD: 2003 October 10 - Peculiar Arp 295
Explanation: A spectacular bridge of stars and gas stretches for nearly 250,000 light-years and joins this famous peculiar pair of galaxies cataloged as Arp 295. The cosmic bridge between the galaxies and the long tail extending below and right of picture center are strong evidence that these two immense star systems have passed close to each other in the past, allowing violent tides induced by mutual gravity to create the eye-catching plumes of stellar material. While such interactions are drawn out over billions of years, repeated close passages should ultimately result in the merger of this pair of galaxies into a larger single galaxy of stars. Although this scenario does look peculiar, galactic mergers are thought to be common, with Arp 295 representing an early stage of this inevitable process. The Arp 295 pair are the largest of a loose grouping of galaxies about 270 million light-years distant toward the constellation Aquarius. This deep color image of the region was recorded in September using the USNO 1 meter telescope near Flagstaff, Arizona.

APOD: 2002 May 2 - Arp 188 and the Tadpole's Tidal Tail
Explanation: In this stunning vista recorded with the Hubble Space Telescope's new advanced camera, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic Tadpole is a mere 420 million light-years distant toward the northern constellation Draco. Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from left to right in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper left. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.

APOD: August 31, 1997 - Arp 230: Two Spirals in One?
Explanation: Is this one galaxy or two? Analysis of Arp 230 has shown evidence that this seemingly single spiral galaxy is actually the result of the recent collision of two spiral galaxies. The slow motion collision took place over about 100 million years and induced a burst of star formation that has begun to subside. The collision apparently had many similarities to the colliding galaxy sequence in the IMAX movie "Cosmic Voyage."

APOD: June 17, 1997 - Arp 220: Spirals in Collision
Explanation: Arp 220 is the brightest object in the local universe. But why does it shine so brightly? Arp 220 was cataloged as a peculiar galaxy in the 1960s. In the late 1980s, it was discovered to be an ultraluminous infrared galaxy and headed a list compiled from observations with the now-defunct IRAS satellite. New observations with the Hubble Space Telescope are quite revealing. Photos by NICMOS in the infrared taken in April and released just last week now better resolve the two colliding spiral galaxies at the center of Arp 220. A result of this spiral collision are fantastic knots of new star formation visible as the bright spots on the above photograph. Below the "half-moon" shaped knot on the right is a massive disk of dust possibly hiding a dying spiral's central black hole. The bright knot to the left is the center of the other broken spiral galaxy. The galaxy cores are about 1200 light years apart and are orbiting each other.

APOD: August 22, 1996 - Arp 230: Two Spirals in One?
Explanation: Is this one galaxy or two? Analysis of Arp 230 has shown evidence that this seemingly single spiral galaxy is actually the result of the recent collision of two spiral galaxies. The slow motion collision took place over about 100 million years and induced a burst of star formation that has begun to subside. The collision apparently had many similarities to the colliding galaxy sequence in the IMAX movie "Cosmic Voyage."