Narrator (Megan Watzke, CXC): Abell 1689 is a massive cluster of galaxies located about 2.3 billion light-years away. An image obtained by the Chandra X-ray Observatory shows hot gas that fills the space between the galaxies. This gas is about 100 million degrees, and therefore glows brightly in X-rays. An image in optical light taken with the Hubble Space Telescope shows the individual galaxies not seen in the Chandra image. Some of the galaxies in the Hubble image that lie beyond the cluster appear as long arcs because their light has been distorted by the immense mass in the intervening galaxy cluster. Taken together, the data from Chandra and Hubble show that Abell 1689 is a galaxy cluster that is in the process of merging with another. Astronomers are studying Abell 1689 to learn more about the distribution of mass as well as the unseen dark matter that is thought to pervade the system.
Revised: November 13, 2008