 |
|
Hubble sees 'Comet Galaxy' being ripped apart by galaxy cluster
March 05, 2007There are many galaxies of different shapes and sizes around us today. Roughly half are gas-poor elliptical-shaped galaxies with little new star formation activity, and half are gas-rich spiral and irregular galaxies with high star formation activity. Observations have shown that gas-poor galaxies are most often found near the centre of crowded galaxy clusters, whereas spirals spend most of their lifetime in solitude.
The mystery, gleaned from deep observations of the Universe, is that when the Universe was half its present age only one in five galaxies was a gas-poor galaxy. So, where do all of today's gas-poor galaxies come from? Scientists suspect that some kind of transforming process must have taken place, but because galaxy evolution occurs over billions of years, scientists have so far not been able to see the transformation at work.
New observations with Hubble by an international team led by Luca Cortese of Cardiff University, United Kingdom, provide one of the best examples to date of this metamorphosis. While looking at the galaxy cluster Abell 2667, astronomers found an odd-looking spiral galaxy (shown here in the upper left hand corner of the image) that ploughs through the cluster after being accelerated to at least 3.5 million km/h by the enormous combined gravity of the cluster's dark matter, hot gas and hundreds of galaxies. "By combining Hubble observations with various ground- and space-based telescopes, we have been able to shed some light on the evolutionary history of galaxies", said Cortese.
As the galaxy speeds through, its gas and stars are being stripped away by the tidal forces exerted by the cluster - just as the tidal forces exerted by the moon and Sun push and pull the Earth's oceans. Also contributing to this destructive process is the pressure of the cluster's hot gas plasma reaching temperatures as high as 10-100 million degrees.
Both processes - the tidal forces and the aptly named "ram pressure stripping" resulting from the action of the hot cluster gas - resemble those affecting comets in our Solar System. For this reason, scientists have nicknamed this peculiar spiral with its tail the "Comet Galaxy".
"This unique galaxy, situated 3.2 billion light-years from Earth, has an extended stream of bright blue knots and diffuse wisps of young stars driven away by the tidal forces and the 'ram pressure stripping' of the hot dense gas," said Jean-Paul Kneib, a study collaborator from the Laboratoire d'Astrophysique de Marseille.
"Millions of now homeless stars have been snatched away from their mother galaxy, which will lead the galaxy to age prematurely," said co-investigator Giovanni Covone of Osservatorio Astronomico di Capodimonte.
Even though its mass is slightly larger than that of the Milky Way, the spiral will inevitably lose all its gas and dust as well as its chance of generating new stars later, and become a gas-poor galaxy with an old population of red stars. "However, in the midst of all this destruction, the cluster's strong forces have triggered a baby-boom of star formation," adds Covone.
Scientists estimate that the total duration of the transformation process is close to one billion years. What is seen now in the Hubble image is roughly 200 million years into the process.
The strong gravitational pull exerted by the galaxy cluster's collective mass has bent the light of other, more distant galaxies and distorted their shapes - an effect called gravitational lensing. The giant bright banana-shaped arc seen just to the right of the centre in the photo corresponds to the magnified and distorted image of a distant galaxy that lies behind the cluster's core.
At the cluster's centre another rare feature can be seen: the vivid blue light from millions of stars created in a so-called cooling flow. Some of the hot cluster gas is cooling in a filamentary structure as it falls into the cluster's core, setting off the birth of lots of bright blue stars outshining their environment. This may be the clearest picture of this phenomenon yet.
The Hubble image was taken by Hubble's Wide Field and Planetary Camera 2 in October 2001 and is a composite of three observations through a blue filter (F450W, 12,000 seconds), a green filter (F606W, 4,000 seconds) and a near-infrared filter (F814W, 4,000 seconds). ESO's Very Large Telescope and the twin Keck Telescopes were used for optical spectroscopy and near-infrared photometry, which helped determine the age of the star-forming region. NASA's Spitzer Space Telescope and Chandra X-Ray Observatory were used jointly to confirm that the activity in the "Comet Galaxy" was due to vigorous star-formation and not a super-massive black hole.
ESA/Hubble Information Centre
As the galaxy speeds through, its gas and stars are being stripped away by the tidal forces exerted by the cluster - just as the tidal forces exerted by the moon and Sun push and pull the Earth's oceans. Also contributing to this destructive process is the pressure of the cluster's hot gas plasma reaching temperatures as high as 10-100 million degrees.
Both processes - the tidal forces and the aptly named "ram pressure stripping" resulting from the action of the hot cluster gas - resemble those affecting comets in our Solar System. For this reason, scientists have nicknamed this peculiar spiral with its tail the "Comet Galaxy".
"This unique galaxy, situated 3.2 billion light-years from Earth, has an extended stream of bright blue knots and diffuse wisps of young stars driven away by the tidal forces and the 'ram pressure stripping' of the hot dense gas," said Jean-Paul Kneib, a study collaborator from the Laboratoire d'Astrophysique de Marseille.
"Millions of now homeless stars have been snatched away from their mother galaxy, which will lead the galaxy to age prematurely," said co-investigator Giovanni Covone of Osservatorio Astronomico di Capodimonte.
Even though its mass is slightly larger than that of the Milky Way, the spiral will inevitably lose all its gas and dust as well as its chance of generating new stars later, and become a gas-poor galaxy with an old population of red stars. "However, in the midst of all this destruction, the cluster's strong forces have triggered a baby-boom of star formation," adds Covone.
Scientists estimate that the total duration of the transformation process is close to one billion years. What is seen now in the Hubble image is roughly 200 million years into the process.
The strong gravitational pull exerted by the galaxy cluster's collective mass has bent the light of other, more distant galaxies and distorted their shapes - an effect called gravitational lensing. The giant bright banana-shaped arc seen just to the right of the centre in the photo corresponds to the magnified and distorted image of a distant galaxy that lies behind the cluster's core.
At the cluster's centre another rare feature can be seen: the vivid blue light from millions of stars created in a so-called cooling flow. Some of the hot cluster gas is cooling in a filamentary structure as it falls into the cluster's core, setting off the birth of lots of bright blue stars outshining their environment. This may be the clearest picture of this phenomenon yet.
The Hubble image was taken by Hubble's Wide Field and Planetary Camera 2 in October 2001 and is a composite of three observations through a blue filter (F450W, 12,000 seconds), a green filter (F606W, 4,000 seconds) and a near-infrared filter (F814W, 4,000 seconds). ESO's Very Large Telescope and the twin Keck Telescopes were used for optical spectroscopy and near-infrared photometry, which helped determine the age of the star-forming region. NASA's Spitzer Space Telescope and Chandra X-Ray Observatory were used jointly to confirm that the activity in the "Comet Galaxy" was due to vigorous star-formation and not a super-massive black hole.
ESA/Hubble Information Centre
Galaxy Cluster News and Current Galaxy Cluster Events RSSHubble sees magnetic monster in erupting galaxy
The Hubble Space Telescope has found the answer to a long-standing puzzle by resolving giant but delicate filaments shaped by a strong magnetic field around the active galaxy NGC 1275. It is the most striking example of the influence of these immense tentacles of extragalactic magnetic fields, say researchers.
Hubble's sweeping view of the Coma Galaxy Cluster
The NASA/ESA Hubble Space Telescope captures the magnificent starry population of the Coma Cluster of Galaxies, one of the densest known galaxy collections in the Universe.
Newly discovered galaxy cluster in early stage of formation is farthest ever identified
UC Irvine scientists have discovered a cluster of galaxies in a very early stage of formation that is 11.4 billion light years from Earth - the farthest of its kind ever to be detected.
Orphan stars found in long galaxy tail
Astronomers have found evidence that stars have been forming in a long tail of gas that extends well outside its parent galaxy. This discovery suggests that such "orphan" stars may be much more prevalent than previously thought.
Dark matter mystery deepens in cosmic 'train wreck'
Astronomers have discovered a chaotic scene unlike any witnessed before in a cosmic "train wreck" between giant galaxy clusters.
X-ray satellites discover the biggest collisions in the Universe
The orbiting X-ray telescopes XXM-Newton and Chandra have caught a pair of galaxy clusters merging into a giant cluster. The discovery adds to existing evidence that galaxy clusters can collide faster than previously thought.
Galaxy Cluster Takes It to the Extreme
Evidence for an awesome upheaval in a massive galaxy cluster was discovered in an image made by NASA's Chandra X-ray Observatory. The origin of a bright arc of ferociously hot gas extending over two million light years requires one of the most energetic events ever detected.
Hubble sees dark matter ring in a galaxy cluster
A team of astronomers used the Hubble Space Telescope to find the best evidence yet for the existence of dark matter, present in the form of a ghostly ring in a galaxy cluster.
Hubble finds ring of dark matter
Astronomers have long suspected the existence of the invisible substance of dark matter as the source of additional gravity that holds together galaxy clusters.
Flies in a spider's web: Galaxy caught in the making
In nature spiders earn our respect by constructing fascinating, well-organised webs in all shapes and sizes. But the beauty masks a cruel, fatal trap. Analogously, the NASA/ESA Hubble Space Telescope has found a large galaxy 10.6 billion light-years away from Earth (at a redshift of 2.2) that is stuffing itself with smaller galaxies caught like flies in a web of gravity.
More Galaxy Cluster News Articles
 | Cosmology: A Very Short Introduction (Very Short Introductions) by Peter Coles Written in simple and accessible language, this non-technical introduction to cosmology, or the creation and development of the universe, explains the discipline, covers its history, details the latest developments, and explains what is known, what is believed, and what is purely speculative. In addition, the author discusses the development of the Big Bang theory, and more speculative modern... |
 | The Cosmic Perspective: Stars, Galaxies and Cosmology by Jeffrey O. Bennett, Megan Donahue, Nicholas Schneider, Mark Voit |
 | Universe: Stars & Galaxies w/Starry Night Enthusiast CD-ROM by Roger Freedman, William J. Kaufmann |
 | Concise Catalog of Deep-sky Objects: Astrophysical Information for 500 Galaxies, Clusters and Nebulae by W.H. Finlay Here is a unique and fascinating reference book for every serious deep-sky observer! Entries for each of more than 500 deep-sky objects provide far more than the usual astronomical data - they also detail, in every case, the most interesting facts. Physical factors, astrophysical information, evolution, unusual features, the list is endless. The objects are all listed in NGC order,... |
 | Schaum's Outline of Astronomy by Stacey Palen Confusing Textbooks? Missed Lectures? Tough Test Questions? Fortunately for you, there's Schaum's Outlines. More than 40 million students have trusted Schaum's to help them succeed in the classroom and on exams. Schaum's is the key to faster learning and higher grades in every subject. Each Outline presents all the essential course information in an easy-to-follow, topic-by-topic format.... |
 | Galaxies by Seymour Simon This close-up look at our own Milky Way and other enormous clusters of stars describes the many different types of galaxies, how they were formed, and how they got their different shapes. "A dazzling photo-essay."--School Library... |
 | Galaxies and Cosmology by Francoise Combes, Patrick Boissé, Alain Mazure, Alain Blanchard Cosmology is the study of nature on the grandest scale we know: that of the Universe itself. This successful and class-tested textbook covers all the essentials: galaxies, their formation, morphology, dynamics, stellar and gaseous structure, and interactions; radio sources, quasars, and other galactic nuclei and their spectra and absorption-line systems; and the interstellar medium and the... |
 | Two-thirds by David P. Myers, David S. Percy |
 | Galaxies and How to Observe Them (Astronomers' Observing Guides) by Wolfgang Steinicke, Richard Jakiel Galaxies are perhaps the most popular of all visual targets that are sought after by visual observers. At present the only way to get up-to-date information, is to query various (often highly technical) speciality books or digging deeply into the Internet. This can be a time consuming and often frustrating task, as the data aren’t often compatible. This book satisfies the need for a... |
| The Cosmic Perspective by Jeffrey O. Bennett |
| © 2008 BrightSurf.com |