Hubble Snaps Rare Aligned Galaxies National Geographic - September 17, 2008
Hubble Snaps Rare Aligned Galaxies National Geographic - September 17, 2008
Thousand-ruby Galaxy: Pinwheel Shines In The Darkness Science Daily - September 3, 2008
Thousand-Ruby Galaxy National Geographic - September 2, 2008
How big can a black hole grow? New Scientist - September 3, 2008
Milky Way's black hole gets extreme close-up New Scientist - September 3, 2008
Closest Look Ever at the Edge of a Black Hole PhysOrg - September 3, 2008
Closest Look Yet at Milky Way's Black Hole Live Science - September 3, 2008
Milky Way's Halo Loaded with Star Streams Live Science - August 16, 2008
Stellar nursery found near Milky Way's violent heart New Scientist - July 24, 2008
The Exploding Star in the Milky Way That Everyone Missed Space.com - July 22, 2008
New Milky Way Map Created; Shows Two Fewer Main Arms National Geographic - June 3, 2008
Milky Way loses two arms MSNBC - June 4, 2008
Black Holes Key to Spiral Arm Hugs Live Science - June 3, 2008
Milky Way's Giant Black Hole 'Awoke From Slumber' 300 Years Ago Science Daily - April 17, 2008
Two Supernova Factories Found In The Milky Way Science Daily - April 2, 2008
Galaxy Evolution Seen in Action BBC - April 1, 2008
Galaxy without dark matter puzzles astronomers New Scientist - February 7, 2008
"Fossil Galaxy" Spotted by Hubble National Geographic - February 7, 2008
Cosmic Finger Taps Our Galaxy's Shoulder Space.com - February 5, 2008
Building Blocks of Life Detected in Distant Galaxy National Geographic - February 5, 2008
Milky Way's antimatter linked to exotic black holes New Scientist - January 22, 2008
Milky Way Has Mysterious Lopsided Cloud Of Antimatter: Clue To Origin Of Antimatter Science Daily - January 15, 2008
Perfectly Aligned Galaxies Found For the First Time - Double Einstein Ring National Geographic - January 12, 2008
Astronomers have found three galaxies in a never before seen perfect alignment
a discovery that may help scientists better understand the mysterious dark matter
and dark energy believed to dominate the universe.The three galaxies are like beads
on a string, one directly behind the other.
Ancestors of Milky Way-Type Galaxies Found, Analyzed National Geographic - January 9, 2008
Milky Way 'ancestors' discovered BBC - January 9, 2008
Galaxy's spiral arms point in opposite directions New Scientist - January 9, 2008
Baby Versions of Milky Way Spotted Live Science - January 9, 2008
Galaxy's antimatter may leak from black holes New Scientist - January 10, 2008
Speeding Star to Escape from Milky Way Space.com - November 29, 2007
Phantom galaxy stages celestial fireworks Guardian - November 30, 2007
Discovering Teenage Galaxies Billions Of Light Years Away Science Daily - November 29, 2007
Dwarf Galaxy I Zwicky 18 National Geographic - October 16, 2007
I Zwicky 18 Wikipedia
Spectroscopic observations with ground-based telescopes have shown that I Zwicky 18 is
almost exclusively composed of hydrogen and helium, the main ingredients created in the Big Bang.
Small 'Hobbit' Galaxies Made Almost Entirely of Dark Matter Live Science - September 12, 2007
Four Galaxies Collide
Four gigantic galaxies have been seen crashing into one
another in one of the biggest cosmic collisions ever seen.
Colossal Four-Galaxy Collision Discovered National Geographic - August 8, 2007
Galaxies clash in four-way merger BBC - August 7, 2007
Four-galaxy collision could form übergalaxy MSNBC - August 7, 2007
Giant Planets More Common, Star Survey Suggests BBC - August 6, 2007
The Four Suns of HD 98800 NASA - July 30, 2007
Streams of Stars Reveal Cannibal Nature of Milky Way Space.com - May 31, 2007
Why Are Galaxies without Black Holes Uncommon? PhysOrg - May 31, 2007
Mystery spiral galaxy arms explained? PhysOrg - April 11, 2007
Chemical composition of stars in clusters can tell history of our galaxy PhysOrg - March 22, 2007
Fundamental Rule Describes All Galaxies Space.com - March 6, 2007
Panorama reveals thousands of growing galaxies New Scientist - March 6, 2007
Galaxy survey focuses on 'pre-teen' years PhysOrg - March 6, 2007
Hubble sees 'Comet Galaxy' being ripped apart by galaxy cluster EurekAlert - March 2, 2007
First X-ray detection of a colliding-wind binary beyond Milky Way PhysOrg - February 16, 2007
New Theory Explains Darkest Galaxies BBC - February 15, 2007
Seven or Eight Dwarf Galaxies Discovered Orbiting the Milky Way PhysOrg - January 9, 2007
Tiny galaxy hosts huge black hole BBC - January 9, 2007
VCC128 is an elliptical dwarf galaxy, about 1% the size of our own Milky Way,
located in the Virgo Cluster, which is about 59 million light-years away.
Large Galaxy Caught in the Making Space.com - October 13, 2006
Hubble photographed the Spiderweb Galaxy, officially MRC 1138-262.
It is 10.6 billion light-years away. The light we see from it emanated
when the universe was only a couple billion years old.
Giant Gas Loops Found in Center of Milky Way, National Geographic- October 4, 2006
Giantic magnetic loops of gas have been discovered
arching out of the heart of our galaxy, mimicking loops of
plasma sometimes seen on the sun, only a trillion times bigger.
New Planet "Bonanza" Discovered at Center of Milky Way National Geographic - October 5, 2006
Hubble Spots 500 Galaxies in Early Universe Space.com - September 22, 2006
Earliest Galaxies in the Universe Spied by Astronomers National Geographic - September 16, 2006
Baby star found near galaxy's violent centre New Scientist - August 15, 2006
The Milky Way over Utah NASA - June 6, 2006
Milky Way is many tentacled beast News in Science - June 5, 2006
Our galaxy is a much wilder looking tentacled beast than suspected,
say astronomers who have used a new technique to map the Milky Way.
Stellar Sound Waves Set Off Supernovas Space.com - February 22, 2006
Sucked in! Our galaxy eats neighbor ABC - February 14, 2006
Astronomers have released new evidence to show that a region
of stars in our galaxy known as the Arcturus stream is the
digested remains of what was once a neighboring galaxy.
Most Milky Way Stars Are Single PhysOrg - January 30, 2006
Exiled Stars: Milky Way Boots Members Space.com - January 27, 2006
Astronomers last year spotted a star leaving the Milky Way Galaxy.
Later one or two more were detected. And today, researchers
announced the discovery of yet two more outbound stars.
Smallest Earth-like planet found BBC - January 25, 2006
Earth's twin found at heart of Milky Way News in Science - January 25, 2006
Scientists find extrasolar planet most like our own MSNBC - January 25, 2006
Microlensing detects faraway world just 5.5 times bigger than our own
Milky Way's Warp Explained Space.com - January 10, 2006
Dark matter may affect our galaxy's warp
Milky Way galaxy is warped and vibrating like a drum UC Berkeley News - January 9, 2006
Atomic gas layer is vibrating like a drum. Vibration consists almost entirely of three notes, or modes.
Man-Made "Star" Illuminates Milky Way's Mysterious Center Scientific American - December 23, 2005
The bar is embedded in the center of the galaxy's spiral arms Space.com August 17, 2005
and cuts across the heart of it all where a supermassive black hole resides
Gemini Uncovers 'Lost City' Of Stars PhysOrg - August 17, 2005
Like archaeologists unearthing a 'lost city', astronomers using the
8-meter Gemini South telescope have revealed that the galaxy
NGC 300 has a large, faint extended disk made of ancient stars,
enlarging the known diameter of the galaxy by a factor of two or more.
- - - -
Hubble discovers galaxies galore MSNBC - August 4, 2005
High Energy Milky Way Reveals 'Dark Accelerators' Science Daily - May 31, 2005
How colliding galaxies built the universe MSNBC - April 2005
Cosmic particle accelerator seen BBC - April 2005
Astronomers have discovered a loop-like structure some
20 light-years across close to the center of the Milky Way
Galactic pancake mystery solved BBC - April 2005
Astronomers have figured out why a series of
small galaxies surrounding the Milky Way are
distributed around it in the shape of a pancake
New Sources of High-Energy Gamma Rays Discovered at Galaxy's Center Scientific American - April 2005
Astronomers Map Chaotic Galaxy's Magnetic Field Scientific American - March 2005
Radio Waves Detected Coming From Center of Galaxy National Geographic - March 2005
Astronomers find star-less galaxy BBC - February 2005
Astronomers say they have discovered an object that appears
to be an invisible galaxy made almost entirely of dark matter
Brightest Galactic Flash Ever Detected Hits Earth Space.com - February 2005
A huge explosion halfway across the galaxy packed so much
power it briefly altered Earth's upper atmosphere in December.
No known eruption beyond our solar system has ever
appeared as bright upon arrival.
Astronomers Spy Galaxy's Strongest Explosion Yet Scientific American - February 2005
Huge 'star-quake' rocks Milky Way BBC - February 2005
See-through Galaxy: Revealing The Milky Way's Center Science Daily - January 2003
The center of our galaxy is hidden behind a "brick wall" of obscuring
dust so thick that not even the Hubble Space Telescope can penetrate it.
Surprising Second Black Hole Found in Milky Way's Center Space.com - November 2004
Puzzling Milky Way Companion Found - Star Clump Space.com - October 2004
Unexpected Beat in Heart of Milky Way Space.com - October 2004
The center of our galaxy is approximately 27,000 light-years away
in the direction of the constellation Sagittarius. At its core, lies a
supermassive black hole surrounded by millions of stars, all huddled
far more closely than in the galactic outskirts where our Sun resides.
Hubble Lifts Fog on Early Universe - Discovery of Powerful Star-forming Galaxies Space.com- September 2004
Astronomers witness huge galactic collision MSNBC
A Cosmic Storm: When Galaxy Collide Space.com
Stars reveal the Milky Way's age BBC - August 2004
estimated by astronomers as being about 13,600 million years old
Chandra captures galaxy cluster forming BBC - August 2004
Hubble sights Milky Way's 'twin' BBC - August 2004
NGC 3949 is a large spiral galaxy and, in astronomical
terms at least, is relatively nearby at around 50 million
light-years away from Earth.
Hubble discovers 100 new planets orbiting stars in our galaxy in galactic bulge BBC - July 2004
If confirmed it would almost double the number of planets known
to be circling other stars to about 230. The discovery will lend
support to the idea that almost everysunlike star in our galaxy,
and probably the Universe, is accompanied by planets.
Milky Way X-ray Mystery Deepens Scientific American - July 2004
What is the glow in the center of our galaxy?
Puzzling Filaments in Milky Way Explained Space.com - June 7, 2004
Origin Of Enigmatic Galactic-center Filaments Revealed Science Daily - June 2004
Brightest Objects are Humdrum Galaxies Space.com - May 2004
Star Birth Gone Wild in 'Cosmic Hurricane' Space.com - May 2004
A shower of hot gas spewed from a galaxy loaded
with pockets of intense star formation offers a
window to the more violent early universe.
Zeroing in on the Milky Way's Black Hole Space.com - April 2004
Survey Finds Dozens of Surprisingly Small Galaxies Space.com - April 2004
Hubble Finds Farthest Galaxies - Strangest Yet Space.com - March 2004
Newfound Galaxy Shatters Distance Record Space.com - March 2004
Distant galaxies line-up in space BBC - February 2004
Astronomers are puzzled by an image of a distant cluster of galaxies in which
they are lined up like a string that is stretched across the Universe.
Hubble sees 'most distant object' BBC - February 2004
The farthest object in the Universe yet detected has been seen by scientists
using the Hubble and Keck telescopes. It is so distant its light must have set
out when the Universe was just 750m years old to reach the Earth now.
Newly Discovered Galaxy Is a Record-Breaker Sci American - February 2004
Galaxies Collide to make Life's Building Blocks Space.com - January 2004
A pair of colliding galaxies is flush with the building blocks for planets and ultimately life
Galaxies in Young Cosmos More Massive and Mature than Expected Space.com - January 2004
The universe is laden with massive galaxies that formed while the
universe was just one billion years old, an era when such mature
galaxies were not expected to exist.
Our Violent Universe: Galaxy Ripped to Shreds Space.com - January 2004
Aliens in our galaxy? Experts map possible hotbeds National Geographic - January 2004
Astronomers See Era Of Rapid Galaxy Formation; New Findings Pose A Challenge For Cold Dark Matter Theory Science Daily - January 2004
New Twists on the Milky Way's Big Black Hole Space.com - November 2003
The supermassive black hole at the center of our Milky Way Galaxy is
heftier than thought and rotates at an amazing clip, new research shows.
Detailed Look at Milky Way Gobbling a Galaxy Space.com - September 2003
Astrophysicists Discover Massive Forming Galaxies September 2003 - Science Daily
Spirals in Nature: The Magical Numbers behind Hurricanes and Galaxies September 2003 - Space.com
Scientists Determine Large Magellanic Cloud Galaxy Formed Similar To Milky Way Science Daily - September 2003
Most distant galaxy detected - 12.8 billion light-years away BBC - March 2003
Milky Way's star 'doughnut' BBC January 2003
Hubble watches galactic dance BBC - December 2002
Galaxy's dark centre exposed BBC October 2002
Spiral galaxy winds up astronomers BBC February - 2002
This galaxy is spiraling backwards
Our galaxy - from the outside February 2002 - BBC News
Telescope snaps 'perfect spiral' BBC News - February 2002
January 10, 2001 - NASA
Although astronomers have taken many stunning pictures of galaxies slamming into each other, this image represents the clearest view of how some interacting galaxies dump material onto their companions. These results are being presented today at the 197th meeting of the American Astronomical Society in San Diego, CA.
Astronomers used the Space Telescope Imaging Spectrograph to confirm that the pipeline is a continuous string of material linking both galaxies.
Scientists believe that the tussle between these compact galaxies somehow created the pipeline, but they're not certain why NGC 1409 was the one to begin gravitationally siphoning material from its partner. And they don't know where the pipeline begins in NGC 1410. More perplexing to astronomers is that NGC 1409 is seemingly unaware that it is gobbling up a steady flow of material. A stream of matter funneling into the galaxy should have fueled a spate of star birth. But astronomers don't see it. They speculate that the gas flowing into NGC 1409 is too hot to gravitationally collapse and form stars.
Astronomers also believe that the pipeline itself may contribute to the star-forming draught. The pipeline, a pencil-thin, 500 light-year-wide string of material, is moving a mere 0.02 solar masses of matter a year.
Astronomers estimate that NGC 1409 has consumed only about a million solar masses of gas and dust, which is not enough material to spawn some of the star-forming regions seen in our Milky Way. The low amount means that there may not be enough material to ignite star birth in NGC 1409, either.
The glancing blow between the galaxies was enough, however, to toss stars deep into space and ignite a rash of star birth in NGC 1410. The arms of NGC 1410, an active, gas-rich spiral galaxy classified as a Seyfert, are awash in blue, the signature color of star-forming regions. The bar of material bisecting the center of NGC 1409 also is a typical byproduct of galaxy collisions.
Astronomers expect more fireworks to come. The galaxies are doomed to continue their game of "bumper cars," hitting each other and moving apart several times until finally merging in another 200 million years. The galaxies' centers are only 23,000 light-years apart, which is slightly less than Earth's distance from the center of the Milky Way. They are bound together by gravity, orbiting each other at 670,000 miles an hour (1 million kilometers an hour). The galaxies reside about 300 million light-years from Earth in the constellation Taurus.
Thousands of galaxies in the supercluster stand behind red and yellow-coloured foreground stars
January 9, 2001 - BBC
Astronomers have identified a supercluster of galaxies that could be the biggest structure anywhere in the observable Universe.
The grouping, which is in the constellation of Leo, is thought to be about 500 million light-years across and about 6.5 billion light-years from Earth. Because in astronomical terms distance equals time, scientists are seeing the supercluster when the Universe was perhaps one-third the age it is now.
The concentration of galaxies was revealed by the light it absorbed from even more distant quasars located behind the supercluster.
Quasars, "active" galaxies that have very bright cores, probably powered by giant matter-sucking black holes, have become useful tools for probing deep space. They help scientists to map the spatial distribution of galaxies, a task that is vital in developing coherent theories to explain why the matter in the Universe is spread out in the way it is.
The supercluster itself also contains an unusually large number of quasars of its own. It has 18 in a swath of space astronomers would normally expect to find only about two to three if there was no galaxy cluster present.
The international team of astronomers that made the latest discovery said the supercluster posed some questions for current cosmological theories.
If the concentration of galaxies was caused by a larger than usual amount of matter in the area, traditional theories of the evolution of the Universe would have difficulty explaining how gravity could pull extremely massive structures together over such a large distance, in such a relatively short time, they said.
"A successful theory has to explain the extremes," said Dr Gerard Williger, from Nasa's Goddard Space Flight Center and the National Optical Astronomy Observatories in Arizona, US.
"Bizarre things like this huge supercluster present a unique opportunity to measure how well quasars and galaxies reveal the mass in such a big region of space, which can then be connected to predictions from theories. The light we are presently observing from this large quasar group had to cross such a vast distance to reach us that it actually left the group before the Earth was formed," said Williger.
"We see these galaxies as they existed billions of years ago. The amount of matter connected with quasars and galaxies at such distances and distant times in the past is probably not the same as we would measure in the local Universe today, so it's very important to find out how much mass we are actually looking at in the supercluster. The first step is to look for signs of extra galaxies in the area, and now we have evidence for a surplus of galaxies."
The research was presented on Monday to a meeting of the American Astronomical Society in San Diego, California, and is being prepared for submission to the Astrophysical Journal.
Working with Luis Campusano of the University of Chile and Roger Clowes and Chris Haines of the University of Central Lancashire in the UK, Williger stressed that the research needed to be confirmed with more data.
Enormously bright objects at the edge of the Universe.
Appear point-like, similar to stars, from which they derive their name (quasar = quasi-stellar). Some quasars shine with the light of a trillion suns. A type of active galaxy powered by supermassive black hole. Quasars can show up intervening galaxies.
An X-ray view of the core of a distant galaxy
November 7, 2000 - BBC
The Chandra X-ray Observatory has seen new details of the jet of super-hot gas shooting from the heart of a quasar.
Quasars are distant galaxies with brilliant cores, thought to be bright because of the colossal energy released when matter is sucked into a black hole.
The jet of gas expelled from quasars, often at velocities very close to the speed of light, have long puzzled scientists.
Astronomers believe the new observations of quasar 3C273, when coupled with optical and radio data, may reveal how such very high-velocity jets are driven.
To the core
"For the first time, Chandra has given us an X-ray view into the area between 3C273's core and the beginning of the jet," said Herman Marshall of the Massachusetts Institute of Technology, US.
"Instead of being void of X-ray emission, Chandra has enabled us to detect a faint, but definite, stream of energy," he added.
Most optical, radio, and earlier X-ray observations of high-powered jets has shown the material emerging in "blobs". The newly discovered, continuous X-ray emission from the core in 3C273 may show scientists what it is that provides the power for the jets.
Astronomers would like to learn why matter is violently ejected from the quasar's core, and then appears to suddenly slow down.
Jet formation
"If there is a slower car in front on a highway, a faster one from behind will eventually catch up and maybe cause a wreck," said Herman Marshall.
"If the jet flow velocity changes, then gas shocks may result, which are akin to car collisions. These gigantic clouds of high-energy electrons, now seen in X-rays by Chandra, may indeed be the result of some sort of cosmic traffic pile-up."
The energy emitted from the jet in 3C273 probably comes from gas that falls towards a supermassive black hole at the centre of the quasar, but is then redirected by strong electromagnetic fields into a jet. However, this process is still poorly understood.
While the black hole itself cannot be seen directly, properties of the hole can be deduced by studying the jet.
Perplexing properties
The quasar 3C273 is no stranger to making astronomical news.
It was first identified in the 1960s and was one of the first objects to be recognised as a "quasi-stellar" object. Its properties were very perplexing.
Only after careful consideration did astronomers determine that 3C273, and others like it, were not nearby stars, but very distant galaxies with incredibly powerful nuclei.
The core of an active galaxy, which may occupy a region of space no bigger than our Solar System, can shine with the luminosity of 20 billion Suns.
November 2, 2000 - CNN
NASA's flagship space observatory has captured a brilliant light display ignited by a violent encounter between two galaxies, scientists said Thursday.
Bright blue and white streaks along the top and right edge of the large spiral galaxy in the central part of the Hubble Space Telescope image mark the path taken by a passing smaller galaxy. The tip of the latter appears in the lower right corner of a more detailed picture, which can be viewed by clicking on the "larger" icon.
The luminous trail reveals the location of new stars in the large galaxy created by the cosmic crash. Dust and gas clouds in both galaxies rammed into each other during the encounter, compressing and heating up the interstellar clouds enough in some cases to spark the formation of hot blue stars through gravitational collapse.
Hubble scientists, who released the image Thursday, likened the brightest patch in the image to a bird's head, leaning over to snatch up some tasty prey.
"We used to call it the golf club but then we turned it upside down and it looked like a bird," said Hubble scientist Keith Noll of the Space Telescope Science Institute in Baltimore, Maryland.
The galactic crash site is about 206 million light years away, in the direction of the constellation Lyra.
Curiously, when galaxies collide, existing stars that comprise most of their luminous mass rarely run into each other. This case offers no exception, said Hubble scientists.
The reason: stars are tiny compared to the distance separating them from one another, making the chances of a direct encounter remote. In our galaxy, for example, the nearest star to our sun is 4.3 light years away: Proxima Centauri, which is part of the Alpha Centauri triple system. Scientists with the Hubble Heritage created the image using archive data recorded by the Hubble telescope in 1996. The orbiting observatory has taken thousands of revealing pictures of the universe since it began operations in 1990.
Part of Stephan's Quintet - a spectacular group of galaxies
October 27, 2000 - BBC
The Hubble Space Telescope has taken a close-up view of one of most exciting star forming regions in the Universe and solved a cosmic mystery.
The image is of a controversial galaxy group of galaxies, called Stephan's Quintet, that has been a puzzle for decades.
Not a problem anymore; galaxy NGC7320
Some astronomers have suggested that the group questions the idea that the Universe is expanding because one of its galaxies is much closer, and so measurements of distances in space cannot be believed.
Hubble has resolved this dilemma showing that most of the galaxies of Stephan's Quintet are not connected.
Distant and distorted
Stephan's Quintet is a group of five galaxies about 270 million light-years away in the constellation of Pegasus.
The galaxy group was the first of its kind to be discovered when it was seen by French astronomer Edouard Stephan in 1877. Today, we know of hundreds of similar groupings, but few are as spectacular as Stephan's Quintet.
Hubble has taken a close-up image of the central part of Stephan's Quintet, giving a magnificent view of this gigantic cosmic collision.
The image shows highly distorted features, dust-lanes crossing between galaxies and long filaments of stars and gas extending far beyond the central regions, show that galaxies have been twisted by the violent encounter between some of them.
The galaxies float through space with distorted shapes caused by tidal interactions.
Cosmic doubt
Observations of Stephan's Quintet had thrown doubt on the long-established connection between an objects distance and its redshift, a relationship caused by the expansion of the Universe.
In 1961 it was discovered that all but one of the galaxies are receding from the Earth at about the same velocity. The discordant galaxy, called NGC 7320, is receding much less rapidly. Some astronomers saw this as evidence that redshift is unrelated to distance, opposing the idea that the Universe is expanding.
Other astronomers countered that NGC 7320 is merely a foreground galaxy, 35 million light years away, projected onto the more distant (270 million light years) compact group by chance.
Mariano Moles from Instituto de Matematicas y Fisica Fundamental in Madrid has studied Stephan's Quintet for many years: "It is a personal pleasure for me to see this magnificent image from Hubble. Stephan's Quintet has been a very puzzling object for many years because of the discordant redshift of NGC 7320."
"Just by looking at this splendid image, it is clear that the redshift discordance of NGC 7320 is now finally resolved. Hubble's resolution is so high that individual stars can be discerned in NGC 7320, showing that it is definitely closer than the more remote, compact group of galaxies."
Other measurements have also shown that the groups two other galaxies in the collection are also just passing and are not bound to the group.
Astronomers have located huge bursts of star formation in the star-tails streaming away from the galaxies.
Pierre-Alain Duc from the Service d'Astrophysique in Saclay, France, says: "The quintet is a prime site for the study of the formation of giant star clusters and even dwarf galaxies. Stars form in bursts triggered by the interaction between the galaxies far from the galactic centres."
May 11, 2000 - Space.com
A new Hubble Space Telescope image released Thursday, May 11 reveals a pair of galaxies, perfectly overlapped to create a beautiful silhouette of dust in the foreground galaxy. Astronomers who discovered the pair say the image is extremely interesting because the luminous background galaxy highlights dust in the foreground galaxy that would otherwise be hidden by the black background of space.
The two galaxies, known as NGC 3314-A and NGC 3314-B, lie close to 140 million light-years away from Earth, in the constellation Hydra. The pair was imaged in April, 1999 by William Keel and Ray White III, University of Alabama astronomers who were actually searching the skies for overlapping galaxies in order to settle a little score.
"Quite a controversy had erupted as to whether there¹s so much dust in galaxies that it completely blocks our view and we don¹t see even half of what¹s there, or whether there¹s a lot less," said Keel. "So we decided to start looking for pairs of overlapping galaxies [to find out]. We went through every galaxy catalog we could find, and we found about a dozen pairs that were big enough to learn something from."
Of the dozen galaxy pairs, Keel and White were able to image three in detail with the Hubble Space Telescope. As it turns out, the overlap between the foreground and background galaxies in NCG 3314 is the most exact ever seen. This exactness has allowed astronomers to measure the amount of dust there is near the center of the foreground galaxy, a feat that is normally impossible to accomplish with solo galaxies due to the black background of space behind them.
The dust of the foreground galaxy, NGC 3314-A, is easily visible to astronomers because it absorbs light emanating from the background galaxy, which lies somewhere between 15 million and 25 million light-years behind NGC 3314-A. "You can see this very red splotch, which is the light from the center of the background galaxy filtering through this huge amount of dust on the way," said Keel. "It turns out that only about 1 percent of the blue light makes it through."
"We desperately hope there¹s nothing special about [these two] galaxies," added Keel. That¹s because he hopes to someday use observations about the dust in NGC 3314-A to describe galaxies the universe over.
But before that can happen, more research in the way of overlapping galaxies must be done. Yet already, some of Keel and White¹s observations about this particular pair have proved quite valuable. "Already, we¹ve shown that the dust in the backlit galaxy is very similar to the dust in our galaxy," said Keel.
Brillianlty bright and clear
March 1, 2000 - BBC
A dramatic new image of the Sombrero galaxy has been obtained by the third large telescope to be commissioned at the Paranal Observatory in the Andes.
Its detail rivals the best that can be obtained from the Hubble Space Telescope which orbits the planet.
Astronomers call the galaxy the Sombrero because of its resemblance to a Mexican hat and have a special affection for it - it is often seen adorning the walls of observatories and universities all over the world.
The image was recorded on 30 January, despite the Paranal Observatory still being under construction. When it is completed later this year, it will comprise four of the most powerful telescopes on our planet.
They will be especially formidable when they all observe in concert forming what is technically known as an interferometer. The first telescope came on-stream in 1998.
Star bulge
The Sombrero galaxy has an unusually large and extended central bulge of stars, as well as dark prominent dust lanes that can be see silhouetted against the stars.
Billions of old stars cause the diffuse glow of the central bulge. Looking at it in detail astronomers can discern myriad individual points of light that are ancient stellar groups called globular clusters.
The young stars of this galaxy may be entwined in the galaxy's spectacular dust rings. The detailed structure of the dust lanes remain a mystery.
Black heart
At the heart of the galaxy is an intense source of radiation at almost all wavelengths. This is believed to be a super-massive black hole.
Astronomers are delighted at the faint detail that can be seen in the image, rivalling anything that can be taken by the Hubble Space Telescope. Many faint and previously unseen wispy structures are detectable in the galaxy as well as numerous dim background galaxies that shine through the outer regions.
The Sombrero galaxy is located in the constellation Virgo, at a distance of about 50 million light-years.
It is sometimes referred to as Messier 104 as it is the 104th object in the famous catalogue of nebulae by French astronomer Charles Messier (1730 - 1817). It was not included in the first two editions, but Messier soon thereafter added it by hand in his personal copy as a "very faint nebula".
Analysis reveals further details
Image processing has been carried out on the new image to reveal new details in the dust lanes.
The complexity of this dust, and the high resolution of the image, is most apparent directly in front of the bright central region of the galaxy but is also very evident as dark absorbing lanes throughout the disk.
This figure is the X-ray spectrum of the central region of the galaxy, NGC 5548. The spectrum shows the number of X rays present at each energy or wavelength, and amounts to a cosmic bar code. It allows scientists to take an inventory of the gas around the giant black hole in the center of the galaxy. The deep valleys in the spectrum are produced when a blanket of warm (few million degree) gas absorbs X rays of specific energies from hotter gas close to the central black hole.
February 22, 2000 - NASA
The Chandra X-ray Observatory has peered into the nucleus of a distant galaxy and detected warm gas flowing away from a black hole.
Using NASA's Chandra X-ray Observatory, an international team of astronomers has made a high-energy bar code for hot gas in the vicinity of a giant black hole. These measurements, the most precise of their kind ever made with an X-ray telescope, demonstrate the existence of a blanket of warm gas that is expanding rapidly away from the black hole.
Jelle Kaastra of the Space Research Organization Netherlands in Utrecht and colleagues used Chandra's the Low Energy Transmission Grating in conjunction with the High Resolution Camera to measure the number of X rays present over a range of energies. With this information they constructed an X-ray spectrum of the source.
Their target was the central region, or nucleus of the galaxy NGC 5548, which they observed for 24 hours. This galaxy is one of a class of galaxies known to have unusually bright nuclei that are associated with gas flowing around and into giant black holes. This inflow produces an enormous outpouring of energy that blows some of the matter away from the black hole.
Astronomers have used optical, ultraviolet, and X-ray telescopes in an effort to disentangle the complex nature of inflowing and outflowing gas at different distances from the black hole in NGC 5548. X-ray observations provide a ringside seat to the action around the black hole. By using the Low Energy Transmission Grating, the Dutch-US-German team concentrated on gas that forms a warm blanket that partially covers the innermost region where the highest energy X-rays are produced.
This might resemble a fried egg you've had for breakfast, but it's actually much larger. In fact, ringed by blue-tinted star forming regions and faintly visible spiral arms, the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. Like NGC 5548, this galaxy is a Seyfert galaxy - a type of active spiral galaxy with a center or nucleus that is very bright at visible wavelengths. Galaxies like NGC 7742 and 5548 are thought to harbor massive black holes at their cores.
As the high energy X rays stream away from the vicinity of the black hole, they heat the blanketing gas to temperatures of a few million degrees, and the blanket absorbs some of the X rays from the central source. This produces dark stripes, or absorption lines in the X-ray spectrum. Bright stripes or emission lines due to emission from the blanketing gas are also present. Since each element has its own unique structure, these lines can be read like a cosmic bar code to take inventory of the gas. The team was able to determine what atoms the gas contains and how many, the number of electrons each atom has retained in the hostile environment of the black hole, and how the gas is moving there. They found lines from eight different elements including carbon, nitrogen, oxygen, and iron. The amount of this gas was found to be about 100 times greater than that found with optical and ultraviolet observations.
November 7, 1999 - NASA
In the direction of the constellation Canis Major, two spiral galaxies pass by each other like majestic ships in the night. The near-collision has been caught in images taken by NASA's Hubble Space Telescope and its Wide Field Planetary Camera 2.
The larger and more massive galaxy is cataloged as NGC 2207 (on the left in the Hubble Heritage image), and the smaller one on the right is IC 2163. Strong tidal forces from NGC 2207 have distorted the shape of IC 2163, flinging out stars and gas into long streamers stretching out a hundred thousand light-years toward the right-hand edge of the image.
Computer simulations, carried out by a team led by Bruce and Debra Elmegreen, demonstrate the leisurely timescale over which galactic collisions occur. In addition to the Hubble images, measurements made with the National Science Foundation's Very Large Array Radio Telescope in New Mexico reveal the motions of the galaxies and aid the reconstruction of the collision.
The calculations indicate that IC 2163 is swinging past NGC 2207 in a counterclockwise direction, having made its closest approach 40 million years ago. However, IC 2163 does not have sufficient energy to escape from the gravitational pull of NGC 2207, and is destined to be pulled back and swing past the larger galaxy again in the future.
The high resolution of the Hubble telescope image reveals dust lanes in the spiral arms of NGC 2207, clearly silhouetted against IC 2163, which is in the background. Hubble also reveals a series of parallel dust filaments extending like fine brush strokes along the tidally stretched material on the right-hand side. The large concentrations of gas and dust in both galaxies may well erupt into regions of active star formation in the near future.
Trapped in their mutual orbit around each other, these two galaxies will continue to distort and disrupt each other. Eventually, billions of years from now, they will merge into a single, more massive galaxy. It is believed that many present-day galaxies, including the Milky Way, were assembled from a similar process of coalescence of smaller galaxies occurring over billions of years.
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