It is smaller than the black holes discovered at the cores of galaxies, but larger than the black holes created when stars burst, with a mass of 100,000 solar masses. As a result, it is one of the few verified intermediate-mass black holes, an entity that astronomers have long sought.
A black hole unlike any other has been found by astronomers. It is smaller than the black holes discovered at the cores of galaxies, but larger than the black holes created when stars burst, with a mass of 100,000 solar masses. As a result, it is one of the few verified intermediate-mass black holes, an entity that astronomers have long sought.
“We have excellent detections of the largest stellar-mass black holes up to 100 times the size of our sun, as well as supermassive black holes in the cores of galaxies that are millions of times the size of our sun, but no measurements of dark between these. That’s a significant difference “Anil Seth, senior author and co-author of the paper, is an associate professor of astronomy at the University of Utah. “This find bridges the gap.”
The black hole was discovered inside B023-G078, a massive star cluster in Andromeda, our nearest neighboring galaxy. B023-G078 was previously assumed to be a globular star cluster, however the astronomers contend that it is really a stripped nucleus. Small galaxies that collided with larger ones and had their outer stars stripped away by gravitational forces are known as stripped nuclei. All that’s left is a small, compact core around the larger galaxy, with a black hole at its center.
“We’ve previously discovered large black holes inside enormous, stripped nuclei far larger than B023-G078. We’ve always suspected that lower-mass stripped nuclei have smaller black holes, but there’s never been direct proof “Renuka Pechetti of Liverpool John Moores University, who began the study while at the University of Utah, is the primary author. “I believe we have finally located one of these items,” says the researcher.
The Astrophysical Journal released the research on January 11, 2022
A long-held suspicion
B023-G078 was classified as a large globular star cluster, which is a spherical group of stars held together by gravity. However, the object’s entire mass, estimated to be about 6.2 million solar masses, has only been calculated from a single sighting. Seth had a sneaking suspicion it was something else for years.
“I knew the B023-G078 object was one of Andromeda’s most massive objects and assumed it would be a candidate for a stripped nucleus. But we needed evidence to back it up. For years, we’d tried to secure additional observations from other telescopes, but my suggestions were always rejected “Seth said. “The Gemini Observatory offered us the opportunity to examine the hypothesis when we detected a supermassive black hole inside a stripped nucleus in 2014.”
Pechetti, Seth, and his colleagues used fresh observational data from the Gemini Observatory and photos from the Hubble Space Telescope to model the object’s light profile and quantify how mass was distributed inside it. The distinctive light profile of a globular cluster is the same shape towards the core as it is in the outlying areas. B023-G078 is unique. The light is circular in the middle and becomes flatter as it moves outwards. The chemical composition of the stars varies as well, with more heavy elements in the stars near the object’s border than those towards the core.
“Essentially, globular star clusters develop at the same period. These stripped nuclei, on the other hand, may undergo several formation events in which gas descends into the galaxy’s core and generates stars. Other star clusters may be drawn towards the galaxy’s core by the galaxy’s gravitational forces “Seth said. “It serves as a kind of dumping ground for a variety of items. As a result, stripped nuclei stars will be more complex than globular cluster stars. That’s precisely what we witnessed in B023-G078.”
The researchers matched their findings to the mass distribution of the object to forecast how quickly the stars should be travelling at any given position inside the cluster. The stars with the greatest velocities were circling the center. When scientists created a model without a black hole, the stars in the center were too sluggish when compared to the data. They achieved speeds that matched the data when they inserted the black hole. The presence of a black hole supports the theory that this item is a stripped nucleus.
“The stellar velocities we’re seeing show us that there’s some type of dark matter right at the core,” Pechetti said. “The formation of large black holes by globular clusters is very difficult. If it’s in a stripped nucleus, though, a black hole must already exist as a relic of the tiny galaxy that collided with the larger one.”
More stripped nuclei, which may host more intermediate mass black holes, are being sought by the researchers. These observations provide a chance to learn more about the black hole population in the cores of low-mass galaxies, as well as how galaxies are constructed from smaller components.
“We know that giant galaxies arise from the merging of smaller galaxies in general,” Seth said, “but these stripped nuclei enable us to discern the intricacies of those prior encounters.”
Sebastian Kamann of Liverpool John Moores University, Nelson Caldwell of the Harvard-Smithsonian Center for Astrophysics, Jay Strader of Michigan State University, Mark den Brok of the Leibniz-Institut für Astrophysik Potsdam, Nora Luetzgendorf of the European Space Agency, Nadine Neumayer of the Max Planck Institute for Astronomie, and Karina Voggel of the Observatoire astronomique de Strasbourg are among the other authors.
