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POPSRepair mission to the Hubble Space Telescope CAPE CANAVERAL, Florida (AP) -- Atlantis' astronauts headed out for another spacewalk Friday, this time to give the Hubble Space Telescope some new, badly needed gyroscopes and batteries. Replacing Hubble's gyroscopes is the top priority for this final repair mission to the 19-year-old observatory. The gyroscopes are part of the telescope pointing system, and half of the old ones are broken. It was the second spacewalk in as many days for the Atlantis astronauts. On Thursday, another two-man team installed a powerful new camera and a computer data unit, after struggling with a stubborn bolt. NASA hoped for an easier, less stressful spacewalk Friday. In all, five spacewalks are planned so that the observatory -- beloved by astronomers and many others for its breathtaking views of the universe -- is at its apex while living out its remaining years. (16 images)
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POPSCosmic crash unmasks dark matter It looks as if it is being seen through lots of little lenses. And each of these lenses represents a piece of dark matter. Astronomers used the Chandra X-ray telescope to map ordinary matter in the merging clusters, mostly in the form of hot gas, which glows brightly in X-rays. As the two clusters that formed MACSJ0025 merged at speeds of millions of kilometres per hour, hot gas in the two clusters collided and slowed down. However, the dark matter kept on going, passing right through the smash-up. The latest astronomical observations suggest that dark matter makes up some 23% of the Universe. Ordinary matter - such as the galaxies, gas, stars and planets - makes up just 4%. The remaining 73% is made up of another mysterious quantity; dark energy, which is responsible for speeding up the expansion of the cosmos.
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