An international team of researchers has discovered that the IRS13 star cluster near the Milky Way's central black hole is surprisingly young. The discovery, made possible by decades of data and the James Webb Space Telescope, challenges current theories of star formation and provides insight into the history and future of the center of the Milky Way.
Researchers have discovered that IRS13, a star cluster near the supermassive black hole Sagittarius A* in the Milky Way, is much younger than expected. This challenges existing theories about star formation near black holes. The research team believes that the formation process of IRS13 was full of turbulence, which may have led to the unexpected appearance of young stars in its vicinity.
An international research team led by Dr. Florian Peißker from the Institute of Astrophysics at the University of Cologne conducted a detailed study of a young star cluster near Sagittarius A* (SgrA*), the supermassive black hole at the center of the Milky Way. Surprisingly, they found that the cluster, named IRS13, was much younger than expected.
IRS13 was discovered more than two decades ago, and until recently it was not possible to identify the cluster's specific members. They achieved this by combining a variety of data collected from multiple telescopes over several decades.
The stars in this cluster are only a few hundred thousand years old, very young by stellar standards, especially compared to our 5 billion-year-old Sun. Interestingly, given the high-energy radiation and the tidal forces of the Milky Way, it is impossible for so many young stars to exist near a supermassive black hole.
The study is titled "Evaporating Massive Embedded Star Cluster IRS13 Near SgrA*. I. Detection of a Rich Population of Dusty Objects in the IRS13 Cluster" (Detection of a Rich Population of Dusty Objects in the IRS13 Cluster) and was published in The Astrophysical Journal.
Multiwavelength view around the supermassive black hole SgrA* (yellow X). Red is stars, blue is dust. Many of the young stars in the star cluster IRS 13 are obscured by dust or obscured by bright stars. Image credit: Florian Peissker/University of Cologne
Another major discovery related to this research was made using the James Webb Space Telescope (JWST). The James Webb Space Telescope has produced the first spectrum of the Milky Way's center without atmospheric interference. This feat is thanks to a prism developed at the Institute of Astrophysics, supervised by Professor Dr. Andreas Eckardt, one of the co-authors of the study. Spectroscopic results show the presence of water ice at the galactic center. This water ice, commonly found around young stellar objects, is further evidence of the youth of some stars near black holes.
Further research by Dr. Peske's team showed that IRS13 experienced a complex formation history. IRS13 appears to have migrated toward the supermassive black hole due to factors such as friction with the interstellar medium, collisions with other star clusters, or its internal dynamics. At some point, the black hole's gravity "captures" the star cluster. This gravitational interaction likely causes a bow-shaped impact at the front of the cluster, like the bow of a ship cutting through water. The resulting surge in dust density may have triggered further star formation, which may also explain why the youngest stars in the cluster are primarily located at the top, or front.
Dr. Peißker said: "The analysis of IRS13 and the corresponding interpretation of the star cluster is the first attempt to unravel the decade-old mystery of unexpectedly young stars in the center of the Milky Way. In addition to IRS13, there is also a star cluster, the so-called S cluster, which is closer to the black hole and also consists of young stars. According to accepted theory, these stars are also significantly younger".
The discovery of IRS13 provides the opportunity for further research to establish connections between the region directly adjacent to the black hole and regions light-years away.
Dr. Michal Zajaček, the second author of the study and a scientist at Masaryk University in Brno, Czech Republic, added: "The IRS13 cluster appears to be the key to unraveling the origin of the dense star population at the center of the Milky Way. We have collected a lot of evidence that very young stars in the range of supermassive black holes may have formed in clusters such as IRS13. This is also the first time that we have been able to identify star populations of different ages - hot main sequence stars and young emerging stars - in a cluster so close to the center of the Milky Way."