00:00Visit Chandra's Beautiful Universe.
00:05NGC 4839
00:09A group of galaxies is plunging into the Coma Galaxy Cluster
00:14and leaving behind an extraordinary tail of superheated gas.
00:18Astronomers have confirmed this is the longest known tail behind a galaxy group
00:23and used it to gain a deeper understanding of how galaxies cluster
00:27some of the largest structures in the universe grow to their enormous sizes.
00:32Astronomers trained NASA's Chandra X-ray Observatory on the galaxy group NGC 4839.
00:40Galaxy groups are collections of about 50 galaxies or less that are bound together by gravity.
00:47Galaxy clusters are even larger and can contain hundreds or thousands of individual galaxies.
00:54Both galaxy clusters and galaxy groups are enveloped by huge amounts of hot gas
01:00that are best studied using X-rays.
01:03These superheated pools of gas, though extremely thin and diffuse,
01:07represent a significant portion of the mass in galaxy groups or clusters
01:12and are crucial for understanding these systems.
01:16NGC 4839 is located near the edge of the Coma Galaxy Cluster,
01:21one of the largest known clusters in the universe, about 340 million light-years away.
01:26As NGC 4839 moves toward the center of the Coma Cluster,
01:31the hot gas in the galaxy group is stripped away by its collision with gas in the cluster.
01:36This results in a tail forming behind the galaxy group.
01:40This comet-like tail is 1.5 million light-years long,
01:44or hundreds of thousands of times the distance between the Sun and the nearest star,
01:49making it the longest tail ever seen trailing behind a group of galaxies.
01:54This gas is a key ingredient in making future generations of stars and planets.
01:59The current brightness of the tail gives astronomers a special chance to study the tail's gas
02:05before it mixes in with the hot gas in the cluster and becomes too faint to study.
02:10The gas in the tail behind NGC 4839 will ultimately merge
02:15with the large amount of hot gas already present in the Coma Cluster.
