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出典:『Wikipedia』 (2010/01/11 17:33 UTC 版)

英語による解説

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NGC 4555 is a solitary elliptical galaxy about 40,000 parsecs (125,000 light-years) across. Observations by the Chandra X-ray Observatory have shown it to be surrounded by a halo of hot gas about 120,000 parsecs across. The hot gas has a temperature of around 10,000,000 kelvins. The galaxy is one of the few elliptical galaxies proven to have significant amounts of dark matter. Large amounts of dark matter are necessary to prevent the gas from escaping the galaxy; the visible mass clearly is not large enough to hold such an extensive gas halo. The dark matter halo is estimated to have 10 times the mass of the stars in the galaxy.