Astronomy Picture of the Day
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September 2, 1995
Hot Gas and Dark Matter
NASA, R. Mushotzky
Is the gravity of the above galaxies high enough to contain the glowing hot
gas? Superposed on an optical picture of a group of galaxies is an image
The X-ray picture, taken by
ROSAT, shows confined
hot gas highlighted in false red colour, and provides clear evidence that
the gravity exerted in groups and clusters of galaxies exceeds all
the individual component galaxies combined. The extra gravity is
the nature and abundance of which is the biggest
mystery in astronomy today.
Tomorrow's picture: Earth's Moon, A Familiar Face
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