Chandra observations of the clouds of hot gas in clusters of galaxies contain clues to the origin, evolution and destiny of the universe:
- Combined X-ray and microwave measurements can yield an estimate of the age of the universe.
- Measurements of the numbers of clusters with extremely hot--greater than 100 million degrees--gas clouds will tell how galaxies formed from the expanding fireball of the Big Bang.
- The pressure in the hot gas is an accurate probe of the amount of dark matter in clusters of galaxies. This knowledge obtained from X-ray measurements can be used to determine whether the universe will expand forever, or will ultimately collapse.
The optical image (left) of the 3C295 cluster shows hundreds of galaxies. The X-ray image shows a vast cloud of fifty million degree gas. The gas cloud, which is visible only with an X-ray telescope,