Subscribe free to our newsletters via your
. 24/7 Space News .


Subscribe free to our newsletters via your




















Spitzer Nets Thousands Of Galaxies In A Giant Cluster

This false-color mosaic of the central region of the Coma cluster combines infrared and visible-light images to reveal thousands of faint objects (green). Follow-up observations showed that many of these objects, which appear here as faint green smudges, are dwarf galaxies belonging to the cluster. Two large elliptical galaxies, NGC 4889 and NGC 4874, dominate the cluster's center. The mosaic combines visible-light data from the Sloan Digital Sky Survey (color coded blue) with long- and short-wavelength infrared views (red and green, respectively) from NASA's Spitzer Space Telescope.
by Staff Writers
Greenbelt MD (SPX) Jun 13, 2007
In just a short amount of time, NASA's Spitzer Space Telescope has bagged more than a thousand previously unknown dwarf galaxies in a giant cluster of galaxies. Despite their diminutive sizes, dwarf galaxies play a crucial role in cosmic evolution. Astronomers think they were the first galaxies to form, and they provided the building blocks for larger galaxies.

They are by far the most numerous galaxies in our Universe, and are an important tracer of the large-scale structure of the cosmos. Computer simulations of cosmic evolution suggest that high-density regions of the Universe, such as giant clusters, should contain significantly more dwarf galaxies than astronomers have observed to date.

A team led by Leigh Jenkins and Ann Hornschemeier, both at NASA Goddard Space Flight Center in Greenbelt, Md., used Spitzer to study the Coma cluster, an enormous congregation of galaxies 320 million light-years away in the constellation Coma. The cluster contains hundreds of previously known galaxies that span a volume 20 million light-years across.

Jenkins, Hornschemeier, and their collaborators used data from Spitzer's Infrared Array Camera (IRAC) to study galaxies at the cluster's center. They also targeted an outlying region with the goal of comparing the galaxy populations in the different locations to see how environmental variations influence the evolution of galaxies. They stitched together 288 individual Spitzer exposures, each lasting 70 to 90 seconds, into a large mosaic covering 1.3 square degrees of sky.

The team found almost 30,000 objects, whose catalog will be made available to the astronomical community. Some of these are galaxies in the Coma cluster, but the team realized that a large fraction had to be background galaxies. Using data taken with the 4-meter (13 foot) William Herschel Telescope on the Canary island of La Palma, team member Bahram Mobasher of the Space Telescope Science Institute, in Baltimore, Md., measured distances to hundreds of galaxies in these fields to estimate what fraction are cluster members.

A surprising number turned out to be Coma galaxies. They appear to be comparable or even smaller in mass to the Small Magellanic Cloud, the Milky Way's second largest satellite galaxy. Jenkins estimates that about 1,200 of the 30,000 faint objects are dwarf galaxies in Coma, many more than have been identified in the past. Given that the observations only cover a portion of the cluster, the results imply a total dwarf galaxy population of at least 4,000.

Spitzer made these discoveries possible because it can survey large areas of sky very effectively. Even better, infrared observations in space can probe more deeply than ground-based near-infrared surveys because the sky background is up to 10,000 times darker.

"With Spitzer's superb capabilities, we have suddenly been able to detect thousands of faint galaxies that weren't seen before," says Jenkins. She is presenting these results on Monday at the American Astronomical Society meeting in Honolulu, Hawaii. The discovery paper will also appear in the Astrophysical Journal.

"We're blowing away previous infrared surveys of nearby clusters," adds Hornschemeier. "Thanks to Spitzer, we can observe nearby clusters such as Coma very deeply in a short amount of time. The total observing time is comparable to just a few nights at a ground-based observatory."

Additional Coma dwarf galaxies might be lurking in the Spitzer data, but more follow-up work is needed to determine how many. Hornschemeier and other astronomers are currently making deeper spectroscopic measurements with the 6.5-meter (21 foot) telescope of the MMT Observatory in Arizona, and the 10-meter (32 foot) Keck telescope in Hawaii, to find out how many of the faintest objects belong to the Coma cluster.

Email This Article

Related Links
NASA/Goddard Space Flight Center
Stellar Chemistry, The Universe And All Within It



Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News


A Team Of Astronomers Identifies The Most Massive Star Ever
Kingston, Canada (SPX) Jun 13, 2007
Although stars with masses reaching up to 150 times the mass of the Sun are expected in the local Universe, no one has reliably found a star exceeding 83 solar masses so far. Until now that is. A team of astronomers from Universite de Montreal has identified the most massive star ever weighed. The details are being presented today by Professor Anthony Moffat at the annual meeting of the Canadian Astronomical Society (CASCA) held at the Royal Military College of Canada in Kingston (ON).







  • Stardust Memories As Space Becomes The Final Frontier In Funerals
  • Vignette Helps NASA Make Giant Leap To The Moon And Beyond
  • Star Trek Fans Beam Into Canadian Wild West
  • Fourteen Space Agencies Sign Joint Exploration Agreement

  • Wandering Poles May Explain Ups And Downs Of Ancient Mars Shoreline
  • Spirit Studies Layered Rocks At Home Plate
  • The Viability Of Methane-Producing Microorganisms In Simulated Martian Soils
  • Taking The Opportunity To Check New Driving Capabilities

  • Dawn Spacecraft Never Damaged Set To Launch July 7
  • Delta 2 Launch To Launch COSMO-SkyMed Satellite
  • Russia Launches Four Satellites Into Orbit For Globalstar
  • Proton-M Carrier With US Telecom Satellite To Lift Off In June

  • NASA Satellites Watch as China Constructs Giant Dam
  • Kalam Calls For Development Of Satellite Systems For Entire Humanity
  • Boeing Launches Italian Earth Observation Satellite
  • Envisat Captures First Image Of Sargassum From Space

  • Full Set Of Jupiter Close-Approach Data Reaches Home
  • A Goofball Called Pluto
  • First Observation Of A Uranian Mutual Event
  • Continuing Our Jovian Journey

  • Spitzer Nets Thousands Of Galaxies In A Giant Cluster
  • A Team Of Astronomers Identifies The Most Massive Star Ever
  • Chronicle Of A Death Foretold
  • Matter Flashed At Ultra Speed

  • A Climate Monitoring Station On The Moon
  • No Plans To Join NASA Lunar Program Says Russian Space Agency
  • Oresme Crater Show Many Signs Of The Early Lunar Heavy Bombardment
  • First China Mission To Moon To Launch By Year End

  • Albertis Seeks Share In Galileo Partner Hispasat As Surrey Welcomes EU Support
  • EU Agrees Galileo Needs Public Bailout
  • EU To Back Galileo Bailout And But Faces Tough Talks On New Funds
  • Latest AeroAstro Asset Tracking Satellite Downlink Decoder Ready For Deployment

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement