A team of researchers at Michigan State University has discovered a new stellar-mass black hole candidate in the globular cluster called M62 in the Milky Way galaxy. The discovery was made using the National Science Foundation’s Karl G. Jansky Very Large Array telescope in New Mexico.
Last year, astronomers led by Laura Chomiuk, an assistant professor of physics and astronomy at MSU, found two black holes in a star cluster, but the team was unable to determine if the black holes' presence was a common occurrence or if it was a unique incident. However, after the discovery of a new black hole candidate called “M62-VLA1,” researchers now believe that it was the former.
“This implies that the discovery of the other black hole, in the globular cluster called M22, was not just a fluke,” Chomiuk said in a statement. “Black holes really may be common in globular clusters… I think it’s safe to say that we have discovered a whole new hunting ground for black holes.”
According to scientists, stellar-mass black holes are made when very big stars collapse into themselves, resulting in a strong gravitational field that not even light can escape. The globular cluster M62 was discovered in 1771 by Charles Messier, and is located in the constellation Ophiuchus, about 22,500 light years from Earth.
“Until recently, astronomers had assumed that the black holes did not occur in globular clusters,” an MSU statement said. “There are so many stars in such a condensed area that they often interact with one another. Massive black holes would have the most violent encounters, ‘sling-shotting’ each other out of the cluster.”
Scientists said, in the study recently published in the Astrophysical Journal, that radio, X-ray, and optical properties of M62-VLA1 are very similar to those of “V404 Cyg,” one of the best-studied quiescent stellar-mass black holes.
“We cannot yet rule out alternative scenarios for the radio source, such as a flaring neutron star or background galaxy; future observations are necessary to determine whether M62-VLA1 is indeed an accreting stellar-mass black hole,” researchers said.