Chandra X-Ray Observatory Observes The Results Of A Galactic Collision

While space is massive, at times, objects floating in its vastness do collide. One such collision is Abell 1775. The system is the result of a smaller galaxy cluster colliding with a larger cluster. Scientists are using x-rays from Chandra and data gathered from other telescopes to piece together information about the collision.

Researchers say galaxy clusters are the largest structures in the universe and are held together by gravity. They can contain hundreds or even thousands of individual galaxies inside giant oceans of superheated gas. In the galaxy clusters, normal matter is primarily in the form of hot gas and stars. The mass of hot gas between the galaxies is much greater than the mass of stars in all of the galaxies within the cluster.

The normal matter is held to the cluster by the gravity of an even larger mass of dark matter. Because of the masses and speeds involved in collisions of this sort, collisions and mergers of galaxy clusters are some of the most energetic events in the universe. Abell 1775 is about 960 million light-years from Earth, and researchers recently announced they discovered a spiral-shaped pattern in the Chandra x-ray data.

That spiral-shaped pattern indicates a turbulent past for the cluster. When two clusters of different sizes have a grazing collision, the smaller cluster begins to move through the larger one, and as the smaller cluster moves through the larger, its hot gases are stripped off due to friction. That leaves a tail trailing behind the cluster. Once the center of the smaller cluster passes through the center of the larger cluster, the gas in the tail starts to encounter less resistance and then overshoot the center of its cluster.

That causes the tail to "slingshot" as it flies to the side, curving as it extends away from the cluster's center. The new image of Abell 1775 has x-rays from Chandra in blue along with optical data from the Pan-STAARS telescope in Hawaii in blue, yellow, and white. Radio data from LOFAR in the Netherlands was added in red. Scientists believe the gas motions inside the cluster are responsible for other structures detected by observing Abell 1775 in radio waves, including two filaments located near the origin of the jet, one of which is labeled in the image above.