Dark matter and ordinary matter separate as two massive galaxies collide

by William Atkins

Friday, 29 August 2008

Page 2 of 3 The dramatic images of the collision of the two galaxies and the separation of dark matter and ordinary matter (because of the collision) are found at the Hubble website of the European Space Agency (ESA)/National Aeronautics and Space Administration (NASA). The website also includes the August 27, 2008 news release “Clash of clusters provides new dark matter.” Bradač added, "Dark matter makes up five times more matter in the universe than ordinary matter. This study confirms that we are dealing with a very different kind of matter, unlike anything that we are made of. And we're able to study it in a very powerful collision of two clusters of galaxies." [MSNBC] The Bradač/Allen team state within their abstract, “We constrain the physical nature of dark matter using the newly identified massive merging galaxy cluster MACSJ0025.4-1222. As was previously shown by the example of the Bullet Cluster (1E0657-56), such systems are ideal laboratories for detecting isolated dark matter, and distinguishing between cold dark matter (CDM) and other scenarios (e.g. self-interacting dark matter, alternative gravity theories).” The researchers used visible-light images from the Hubble Space Telescope to determine the total mass distribution of the galactic cluster concerning both dark matter and ordinary matter. Hubble also was able to map the dark matter using the scientific technique known as gravitational lensing—a technique in which light can be analyzed as it is “bent” around a massive object as seen between the source of the light and observers of the light (astronomers on Earth) The images show ordinary matter in the color "blue." The Chandra X-ray Observatory was able to image the hot gas of the ordinary matter as it spewed out x-ray radiation. These images are shown in the color "pink." They continue to state, “MACSJ0025.4-1222 consists of two merging subclusters of similar richness at z=0.586. We measure the distribution of X-ray emitting gas from Chandra X-ray data and find it to be clearly displaced from the distribution of galaxies. A strong (information from highly distorted arcs) and weak (using weakly distorted background galaxies) gravitational lensing analysis based on Hubble Space Telescope observations and Keck arc spectroscopy confirms that the subclusters have near-equal mass.” The researchers found that MACSJ0025-1222 is about one quadrillion times the mass of Earth’s Sun. The two galaxies that are forming the galactic cluster are merging together at millions of kilometers per hour. As this collision occurs, ordinary matter slows down in speed while dark matter is unaffected by the action—it moves through without any visible change in speed. Page three concludes their abstract statement. << First page <   1 2 3 Next page > Last page - Post your comment >>

 

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