Hubble has discovered a long-sought-after intermediate-sized black hole

The latest data from the Hubble Space Telescope provide the strongest evidence for intermediate mass black holes in the universe. Hubble confirmed the presence of such a black hole in one of the dense star clusters.

Intermediate-mass black holes (IMBH) have long been a sought-after "missing link" for the evolution of black holes. Only a few candidates for this type of black hole have been discovered so far. These objects are smaller than the supermassive black holes discovered in the centers of large galaxies, but also larger than the star-mass black holes formed by the collapse of the massive star. The black hole observed by scientists has a mass of about 50,000 solar masses.

Intermediate black holes are very secretive objects and they are extremely difficult to find. For this reason, scientists must eliminate any other alternative before they announce that they have discovered IMBH. It was Hubble's telescope that allowed us to do this, 'says Dacheng Lin of the University of New Hampshire, lead author of the study.

Lin and his team used Hubble to observe the object previously observed with the Chandra X-ray Observatory and the XMM-Newton telescope, which is equipped with three x-ray telescopes for long, uninterrupted observations.

Performing subsequent observations in the X-ray range allowed us to understand the total amount of energy released. Thanks to this, we are able to estimate what star was torn apart by a black hole - says Natalie Webb from the University of Toulouse.

In 2006, these satellites recorded a strong X-ray burst. At that time, no one knew if the source of the flare was inside or outside our galaxy. The researchers concluded that the cause of the flare was the tearing of the star as it passed near a massive object, e.g. a black hole.

To the surprise of scientists, it turned out that the source of X rays with the charming name 3XMM J215022.4-055108 is not in the center of the galaxy, where usually there are massive black holes. Researchers began to suspect that the source might be an intermediate black hole, but first they had to eliminate another possible source of X-ray flare: the neutron star in the Milky Way.

By directing the Hubble mirror to the source, astronomers decided to pinpoint its location. Accurate, high-resolution images have confirmed that the X-rays do not come from an isolated source in our galaxy, but from a distant, dense cluster of stars on the outskirts of another galaxy. This is exactly where astronomers expected to find IMBH evidence. Earlier studies conducted with Hubble indicate that the more massive the galaxy is, the more massive its central black hole is. Therefore, the results obtained by the researchers indicate that the 3XMM J215022.4-055108 star cluster may be the nucleus of a low-mass dwarf galaxy that has been torn apart by interaction with another larger galaxy.

IMBH is very difficult to find because they are smaller and less active than supermassive black holes. There are not many sources of matter in their surroundings, and their gravitational pull is not strong enough to attract more stars and other interstellar matter that would emit an X-ray glow. For this reason, astronomers must catch IMBH in the act when they are just devouring a passing star. Lin and his colleagues analyzed the data archive from the European XMM-Newton X-ray telescope, searching hundreds of thousands of sources trying to find strong evidence for the presence of the IMBH candidate. Once they were found, the X-ray glow from the torn star allowed astronomers to estimate the mass of the black hole.

Confirming the existence of one black hole of intermediate mass means that there can be many more in outer space, and we will see them only when some unlucky stars get too close to them and burst.

Hubble has discovered a long-sought-after intermediate black hole