Saturday, March 28, 2009

The NASA/ESA Hubble Space Telescope provides new evidence for dark matter around small galaxies


These four dwarf galaxies are part of a census of small galaxies in the tumultuous heart of the nearby Perseus galaxy cluster. The galaxies appear smooth and symmetrical, suggesting that they have not been tidally disrupted by the pull of gravity in the dense cluster environment. Larger galaxies around them, however, are being ripped apart by the gravitational tug of other galaxies. The images, taken by NASA/ESA's Hubble Space Telescope, are evidence that the undisturbed galaxies are enshrouded by a "cushion" of dark matter, which protects them from their rough-and-tumble neighborhood. Dark matter is an invisible form of matter that accounts for most of the Universe's mass. Astronomers have deduced the existence of dark matter by observing its gravitational influence on normal matter, consisting of stars, gas, and dust. Observations by Hubble's Advanced Camera for Surveys spotted 29 dwarf elliptical galaxies in the Perseus Cluster, located 250 million light-years away and one of the closest galaxy clusters to Earth. Of those galaxies, 17 are new discoveries. The images were taken in 2005.Peering into the tumultuous heart of the nearby Perseus galaxy cluster, Hubble discovered a large population of small galaxies that have remained intact while larger galaxies around them are being...

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Swift Satellite records early phase of gamma ray burst

UK astronomers, using a telescope aboard the NASA Swift Satellite, have captured information from the early stages of a gamma ray burst - the most violent and luminous explosions occurring...

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