A Tour of Galaxy Gathering Brings Warmth

Using NASA's Chandra X-ray Observatory and other telescopes, a team of astronomers has studied two galaxy groups that are smashing into each other at a remarkable speed of about 4 million miles per hour. This could be the most violent collision yet seen between two galaxy groups. The system is called NGC 6338, which is located about 380 million light years from Earth.

The majority of galaxies do not exist alone. Rather, they are bound to other galaxies through gravity either in relatively small numbers (known as "galaxy groups") or much larger concentrations (called "galaxy clusters") of hundreds or thousands of galaxies. And, sometimes, these collections of galaxies themselves are drawn toward one another by gravity and eventually merge.

By studying systems like NGC 6338, astronomers are trying to better understand how some of the very biggest objects in the Universe grow and evolve over time. The researchers in this study estimate that the total mass contained in NGC 6338 is about 100 trillion times the mass of the Sun. This significant heft, roughly 83% of which is in the form of dark matter, 16% is in the form of hot gas, and 1% in stars, indicates that this galaxy group is destined to become a galaxy cluster in the future. This will be its fate as the collision and merger in NGC 6338 is completed and the system continues to accumulate more galaxies through gravity.