A medium-sized black hole has been discovered just 6000 light-years away from us, in our cosmic backyard. Astronomers have identified hundreds of stars in the constellation of Scorpius, all pointing in a single direction towards an intermediate-mass black hole.
“It is too small for us, and we are unable to explain if it is a single black hole” said Eduardo Vitral, an astrophysicist at the Space Telescope Science Institute in a statement (rif.) on May 23. “Alternatively, there might be a stellar mechanism that we are not aware of, at least within the current understanding of physics“.
Black Holes Near Us
A significant portion of black holes discovered so far can be classified into two dimensions. There are small black holes with masses ranging from 10 to 100 times that of the Sun, and there are giant black holes that are millions or even billions of times heavier than our star. Intermediate-sized black holes, according to astronomers, reside at the centers of small galaxies. They are much more elusive and challenging to detect due to the lack of explanations regarding their formation and the difficulties in accurately measuring their mass.
While the evidence remains inconclusive, astronomers confirmed in 2014 that one of these intermediate-mass black holes was lurking near Earth. Now, Vitral’s team believes they have identified another black hole in our cosmic backyard. After analyzing 12 years of data from the Hubble Space Telescope of the stellar cluster M4, astronomers are almost certain that an intermediate-mass black hole, approximately 800 times the mass of the Sun, is at the center of the cluster.
Like all black holes, this latest one cannot be directly observed. The team used data from the European Space Agency‘s (ESA) Gaia spacecraft to study the chaotic motion of stars at the center of M4. Like bees around a beehive, these stars are trapped in the gravitational field of the black hole.
Confirmation of the Discovery
While the discovery is awaiting confirmation, models show that such a single, compact, and highly massive region cannot be formed through other processes. Vitral’s team conducted numerical simulations to see if a mass of 800 solar masses could be created by a group of smaller black holes. However, they discovered that what Hubble detected is more compact than what the simulations are capable of producing.
“If the object is not a single intermediate-mass black hole, it would require around 40 smaller black holes, even packed within a space of just one-tenth of a light-year, to produce the observed stellar motions” the team members wrote in the same statement. “The consequences would be that they would merge and/or be expelled in an interstellar pinball game”.