[an error occurred while processing this directive]
Chandra X-ray Observatory - HomeAbout The ChandraEducational MaterialsField GuidePhoto AlbumPress RoomResources
Chandra X-ray Observatory - HomeChandra Field Guide - You are here
[an error occurred while processing this directive]
ObservatoryAbout X-ray AstronomyX-Ray SourcesSolar SystemNormal Stars & Star ClustersWhite Dwarfs & Planetary NebulasSupernovas & Supernova RemnantsNeutron Stars/X-ray BinariesBlack HolesNormal Galaxies & Starburst GalaxiesQuasars & Active GalaxiesGroups & Clusters of GalaxiesCosmology/Deep Fields/X-ray BackgroundMiscellaneousBrown Dwarfs Gamma Ray Bursts
Web Site ToolsVisit the Chandra ChroniclesEmail NewsletterSite MapNew & NoteworthyImage Use PolicyQuestions & AnswersGlossaryDownload Guide

Groups & Clusters of Galaxies

Galaxy clusters are the largest gravitationally bound objects in the universe. They have three major components:
  1. Hundreds of galaxies containing stars, gas and dust;
  2. Vast clouds of hot (30 - 100 million degrees Celsius) gas that is invisible to optical telescopes;
  3. Dark matter, a mysterious form of matter that has so far escaped direct detection with any type of telescope, but makes its presence felt through its gravitational pull on the galaxies and hot gas.
T he hot gas envelopes the galaxies and fills the space between galaxies. It contains more mass than all the galaxies in the cluster. Although the galaxies and hot gas clouds are very massive, scientists have determined that about 10 times more mass is needed to hold the cluster together. Something, namely dark matter must exist to provide the additional gravity.

Hydra A ClusterHydra A Cluster
Comparison of optical image from La Palma & B.McNamara (left) and X-ray image from Chandra (right) of the Hydra A cluster of galaxies. This cluster is so large that it takes light millions of years to cross it.
Astronomers think that galaxy clusters form as clumps of dark matter and their associated galaxies are pulled together by gravity to form groups of dozens of galaxies, which in turn merge to form clusters of hundreds, even thousands of galaxies.

The gas in galaxy clusters is heated as the cluster is formed. This heating can be a violent process as gas clouds enveloping groups of galaxies collide and merge to become a cluster over billions of years.

Page 1 | 2 | 3


[an error occurred while processing this directive]
  separator line
CXC Home | Public Info & Education | Search | Help | Site Map | Image Use | Privacy
New & Noteworthy | Guestbook | Multimedia | Downloads | Ecards | Glossary | Q&A


  [News by email: Chandra Digest]
[Contact us: cxcpub@cfa.harvard.edu]
NASA's Home PageSmithsonian's Home PageCXC Home Page Image Map for NASA's, Smithsonian and Chandra's Home Pages
  Harvard-Smithsonian Center for Astrophysics
60 Garden Street, Cambridge, MA 02138 USA
Phone: 617.496.7941 Fax: 617.495.7356


Text Size:
normal font large font larger font
Operated for NASA by SAO
This site was developed with funding from NASA under Contract NAS8-39073.
Revised: August 01, 2005 Wednesday, 02-Oct-2013 13:36:43 BST