A monstrously large cluster of galaxies is devouring a close-by smaller galactic grouping, causing it to blast out a record-breaking tail of hot gas from its rear. At 1.5 million light-years-long, the tail is the most important tendril of gas ever seen emerging from a galactic group.
Astronomers had previously seen the tail behind NGC 4839 but had estimated it to be just around a million light-years long, a size more in step with the gas tails seen around other similar events that are inclined to be between 800,000 and a million light-years long.
Observations of the feeding cluster and its unlucky cosmic prey made with NASA’s Chandra X-ray Observatory and other telescopes didn’t just prove that the tail is a cosmic record breaker, nevertheless, but could also disclose to scientists how these huge conglomerations of galaxies grow.
The Coma cluster, positioned around 340 million light-years away from Earth, is one among the most important galactic clusters known to astronomers containing around 1,000 individual galaxies. The cluster is steadily growing as one other galaxy group, called NGC 4839, is falling into it at a rate of thousands and thousands of miles per hour.
Galactic groups like NGC 4839 contain around 50 galaxies, while galactic clusters just like the Coma cluster can contain tons of and even 1000’s of galaxies, based on a statement from the Chandra X-Ray Observatory. One thing these different-sized collections of galaxies have in common is the large amounts of superheated gas that envelop them. Though nebulous and diffuse, these clouds of gas still account for an awesome deal of the mass in each galaxy clusters and groups, and which means studying this gas is important in understanding them.
The absorption of NGC 4839 by the Coma cluster could help astronomers understand the processes galaxy groups undergo as they merge. As NGC 4839 moves to the middle of the cluster that’s swallowing it, the galactic group is being stripped of its gas envelope because it collides with the recent gases of the larger cluster. This violent process is what’s creating the huge gas tail behind NGC 4839, which is hot enough to glow brightly.
The brightness of the tail, which is long enough to stretch between the sun and the closest star to our solar system and back again tons of of 1000’s of times over, offers astronomers a singular opportunity to check the physics at play in such events. That is before the tail mixes with the large reservoir of gas of the Coma cluster and cools to the purpose that it is simply too faint to be seen.
The team of astronomers studied the gas in front of NGC 4839, finding shock waves that indicate that the galactic grouping is moving into the Coma cluster at a speed of around 3 million miles per hour (4.8 million km/h), or about 4,000 times as fast because the speed of sound.
The scientists also examined the extent of turbulence within the tail of gas, which indicated that heat conduction in NGC 4839 is low. While observing the tail, the scientists found structures on one side of the gas called Kelvin-Helmholtz instabilities. These instabilities are sometimes brought on by adjoining layers moving gas or fluid traveling at different speeds and, on this case, indicate the presence of either a weak magnetic field or a low level of viscosity within the tail, a measure of how a fluid resists flowing (so water has a lower viscosity than molasses).
The team’s research was presented by the University of Alabama at Huntsville’s Stephen Walker on Tuesday (June 6) on the 242nd meeting of the American Astronomical Society in Albuquerque, Latest Mexico.
The findings are also detailed in a paper published on the open-source research repository ArXiv.
