A newly identified small star system orbiting the Milky Way suggests the existence of a new type of faint satellite system orbiting the larger galaxy, astronomers report.
Researchers recently announced the discovery of Ursa Major III/UNIONS 1 (UMa3/U1), the faintest and least massive star system ever discovered.
“This object is so small that its long-term survival is quite surprising.”
The newly discovered system is just 20 light years across (more than 58.7 trillion miles) and contains only about 60 “mature” stars. Maturity in this case means age of 10 billion years or more. Its mass is one-fifteenth that of the faintest dwarf galaxy.
Researchers discovered UMa3/U1 with the Deep Imaging Multi-Object Spectrograph (DEIMOS) at W.M. Keck Observatory in Hawaii, the Ultraviolet and Near-Infrared Optical Northern Survey (UNIONS) of the Canada-France-Hawaii Telescope, and the University of Hawaii Astronomy Research. Panoramic Survey Telescope and Rapid Response System (Pan-STARRS).
“Uma3/U1 has such a small number of stars that some may wonder if it’s just a coincidence of similar stars,” says Professor of Astronomy and Physics at Yale University’s School of Arts and Sciences. said study co-author Mara Geha.was announced on astrophysical journal.
“Mr. Keck was critical in showing that this was not the case,” Mr. Geha said. “Our DEIMOS measurements clearly show that all stars move through space at very similar speeds and appear to share similar chemical properties.”
For now, this new system has two names. That’s because astronomers have not yet been able to confirm whether it is a dwarf galaxy (named after the constellation Ursa Major) or a star cluster (named after the survey). discovered, UNIONS).
At the heart of this question is the possibility that dark matter, an invisible substance thought to be the invisible “scaffolding” of the universe, is involved.
“Interestingly, the tentative spread in interstellar velocities in this system may support the conclusion that UMa3/U1 is a dark matter-dominated galaxy. This intriguing possibility will be explored in further Keck observations. We want to examine it closely,” says graduate student William Cerny. Geha’s research group and his second author of the new study.
“This object is so small that its long-term survival is very surprising,” Cerny added. “It might have been expected that intense tidal forces from the Milky Way’s disk had already torn the system apart, leaving no observable debris.
“The fact that the system appears to be intact raises two equally interesting possibilities: Either UMa3/U1 is a small galaxy stabilized by large amounts of dark matter, or This is a star cluster that we observed at a special time.
The answer could have implications far beyond the system’s final name.
The standard cosmological model of the universe, known as the lambda cold dark matter model, states that when galaxies like the Milky Way formed, they had enough gravity to attract hundreds of small satellite star systems down to very small masses. and predict that it will continue to exist. Orbiting larger galaxies.
If UMa3/U1 is a galaxy, its existence means that no such faint satellite galaxy has yet been discovered.
“Whether future observations confirm or deny that this system contains large amounts of dark matter, we remain hopeful that this object is just the tip of the iceberg, a new type of dark matter.” “We’re very excited about the possibility that this is the first example of extremely dark matter in a faint star system that has so far eluded detection,” Cerny said.
Simon Smith, a graduate student at the University of Victoria, is the study’s lead author.
sauce: yale university
