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The black line is the newly discovered giant Coma Stream. This line is ten times the length of our Milky Way Galaxy, and is located about 300 million light-years between galaxies (yellow spots). Credit: William Herschel Telescope/Roman et al
To their surprise, an international team of researchers discovered a giant, extremely faint stream of stars between galaxies. While jets are already known in our own galaxy and in nearby galaxies, this is the first time a jet has been observed running between galaxies. It is the largest current discovered so far. The astronomers published their findings in the journal Astronomy and astrophysics.
The first observations were made using the relatively small 70-cm diameter telescope of astronomer Michael Rich in California (USA). Next, the researchers focused the 4.2-meter William Herschel Telescope (La Palma, Spain) on the area. After processing the image, they saw an extremely faint stream more than 10 times the length of our Milky Way Galaxy. The stream appears to float in the middle of the cluster’s environment, and is not associated with any galaxy in particular. Researchers have called it the Giant Coma Stream.
“This giant stream crossed our path by chance,” explains lead researcher Javier Roman. It is affiliated with the University of Groningen (Netherlands) and the University of La Laguna in Tenerife (Spain). “We were studying star halos around large galaxies.”
The discovery of the giant coma stream is remarkable because it is a rather fragile structure amidst a hostile environment of galaxies that mutually attract and repel. “At the same time, we have been able to simulate such huge flows in the computer,” explains co-author Reinier Pelletier (University of Groningen, Netherlands). “So we expect to find more of them. For example, if we search with the future 39-meter ELT and when Euclid begins data production.”
With future large telescopes, researchers not only hope to discover new giant streams; They also want to enlarge the Giant Coma Stream itself. “We would like to observe individual stars in and near the stream and learn more about dark matter,” says Pelletier.
The Coma Cluster is one of the best-studied galaxy clusters. It contains thousands of galaxies located about 300 million light-years away from Earth, in the direction of the northern Coma Berenice constellation. In 1933, Swiss astronomer Fritz Zwicky showed that galaxies in the cluster move very quickly if only the amount of visible matter is taken into account. He discovered that there must be dark matter keeping things together. The exact nature of dark matter is still unknown.
more information:
Javier Roman et al., Giant Thin Stellar Stream in the Coma Galaxy Cluster, Astronomy and astrophysics (2023). doi: 10.1051/0004-6361/202346780, www.aanda.org/10.1051/0004-6361/202346780. on arXiv: doi: 10.48550/arXiv.2305.03073
