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Astronomers have discovered the faintest and lightest satellite galaxy ever discovered. milky way. This unusual discovery could represent a new type of impossibly faint, dark matter-dominated star system that has so far eluded detection.
The newly discovered star system, tentatively named Ursa Major III/Unions 1 (UMa3/U1), is located in the constellation Ursa Major, about 30,000 light-years from the Sun. It is the newest of at least 50 satellite galaxies in our galaxy. Even the smallest of these galaxies contain anywhere from thousands to billions of stars.
In contrast, the newly discovered system has only 60 stars. As a result, its mass is only 16 times that of the Sun, scientists report in a new study. For comparison, the Milky Way’s mass is about 1.5 trillion times that of our star. NASA.
UMa3/U1 also overturns the conventional image of a galaxy with a distinctive shape.
“This discovery could challenge our understanding of galaxy formation, and perhaps even the definition of ‘galaxy.'” Simon Smithsaid the study’s lead author, a graduate student at the University of Victoria in Canada, in a paper. statement. “UMa3/U1 has evaded detection until now due to its extremely low luminosity.”
Related: A 13 billion-year-old ‘star stream’ discovered near the center of the Milky Way galaxy may be the earliest component of our galaxy
Scientists found that in data collected by the Canada-France-Hawaii Telescope (CFHT) project, the Ultraviolet and Near-Infrared Optical Northern Survey, which uses three Hawaii-based telescopes to study the northern sky. UMa3/U1 was discovered for the first time as a cluster of bright stars spanning 10 light years. telescope. The study, published in January, said follow-up observations using the W.M. Keck Observatory confirmed that the stars are gravitationally bound and have similar chemistry. astrophysical journal.
Astronomers are puzzled as to how this tiny UMa3/U1 has remained intact for at least 10 billion years. This is the estimated age of the star’s inhabitants, which is more than twice the age of our Sun, which is 4.6 billion years. From observations of other eccentric stars in the Milky Way, astronomers know that our galaxy’s gravity, also known as tidal forces, has previously torn apart dwarf galaxies that have come too close. For example, some well-known cannibal galaxies are: Gaia Enceladusour home galaxy was torn apart about 8 billion to 10 billion years ago.
But even though UMa3/U1’s orbit passes through the Milky Way’s inner region, where the galactic tidal forces are strongest, the dwarf galaxy appears to have escaped destruction for a long time.
“This object is so small that its long-term survival is quite surprising.” Will CernyHe is a graduate student in Yale University’s astronomy department and a co-author of the study, said in a statement. “UMa3/U1 is either a small galaxy stabilized by large amounts of dark matter, or it is a star cluster that we observed at a very special time before its imminent demise.”
The former possibility is particularly interesting. That’s because astronomers have so far not been able to detect galaxies elsewhere in the universe. dark matter, an invisible substance that is thought to make up the majority of matter in our universe. If dark matter indeed plays a role in holding the newly discovered star system together, future observations could provide valuable clues about its composition and behavior, the study authors said. .
“Whether or not future observations confirm 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 extreme “We are very excited that this may be the first example of dark matter in a faint star system that has so far evaded detection.” Cerny concluded.
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