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ESA / Hubble, M. Kornmesser
The black hole “lit up” when it began to devour a nearby star (artist’s drawing)
A team of astronomers has discovered the strongest evidence to date of the existence of a class of black holes, which until now remained elusive.
This class of medium-mass black holes is considered the most curious, so scientists were so inspired when one of them revealed its existence by starting to devour a star that was too close to it.
It is impossible to directly observe black holes, and scientists draw conclusions about their existence and structure by indirect methods.
Medium-weight black holes are primarily interesting in that they are considered the missing link in understanding the process of star evolution.
“Medium-sized black holes are very secretive objects, so before you establish that we are dealing with it, it’s important to carefully consider and cut off all other possible explanations for what we discovered,” says Dr. Dacheng Lin, head of the research team at the University New Hampshire. “That’s exactly what Hubble’s telescope allowed us to do with our candidate.”
Back in 2006, NASA’s Chandra X-ray orbital observatory and the XMM-Newton European Space Agency X-ray space telescope noticed a powerful flash of cosmic radiation called 3XMM J215022.4-055108.
The nature of this outbreak, according to Dr. Lin, implied only two possible options: it was either a distant (outside our Galaxy) medium-sized black hole devouring a star or a cooling neutron star in our Galaxy. “
Neutron stars, according to modern concepts, are the remains of a former star compressed to a tiny size that arose after its explosion.
What is a black hole?
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NASA GSFC / Jeremy Schnittman
Black holes can have different sizes; the class of medium-massive holes is considered the rarest (fig. artist)
- A black hole is a region of space-time, in which the gravitational force is so great that no objects or waves, including light, can leave it
- Despite the name, the black hole is actually not empty from the inside. On the contrary, it is filled with a huge mass of matter, compressed in a small volume, which creates a huge force of attraction
- Around the black hole is an area called the event horizon. This is an imaginary boundary in space, the “point of no return”, after crossing which it is no longer possible to escape from the gravitational trap
To understand which of the two possible options they are dealing with, astronomers sent the Hubble Space Telescope to the source of the x-ray flare.
The telescope allowed us to state with a high degree of certainty that the source of the flare was not in the Milky Way region, but came from a distant and dense cluster of stars on the outskirts of another galaxy. It was in this place that astronomers expected to find a black hole of medium mass.
According to Dr. Lin, the Hubble telescope has practically confirmed this assumption. Supermassive black holes are often located in the centers of galaxies. For example, our native galaxy Milky Way has its own supermassive hole called Sagittarius A *.
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NASA / ESA / D. LIN (UNH)
The discovered black hole (circled) is located on the outskirts of a distant galaxy.
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ESA
An X-ray flash photo was found among thousands of images taken by the XMM-Newton Orbital Observatory (artist’s drawing)
Finding medium-weight black holes is much more difficult. Their gravity is not so powerful – which means that the activity of space processes available for observation is much lower. In addition, they are located in areas with rather sparse matter: in other words, stars that could be attracted and absorbed are rarely found nearby — namely, this process gives rise to a powerful flash of x-ray radiation.
In fact, astronomers had to literally catch such a black hole red-handed when it devours a random star.
In search of a suitable candidate, Dr. Lin and his colleagues scanned thousands of photographs taken by the XMM-Newton Observatory. The X-ray glow of a torn apart star allowed them to establish the mass of this black hole, which is 50 thousand times greater than the mass of our Sun.
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NASA
The source of the x-ray flare and, accordingly, the black hole itself, were found using the Hubble telescope
Scientists have come across candidates for the title of a black hole of medium weight, but, according to Dr. Lin, the star-eating example was the most convincing. Meanwhile, these black holes can provide a key to understanding the evolution of themselves and the cosmos as a whole.
For example, researchers are very interested in the question of whether supermassive black holes form from medium-mass holes over time, gradually increasing in size. Astronomers also want to understand how medium-mass holes form and how often they arise in dense clusters of stars, like this one.
“Studying the origin and evolution of medium-sized black holes will ultimately explain how supermassive black holes appeared in the centers of large galaxies,” said Dr. Liny’s colleague at the University of Toulouse, Dr. Natalie Webb.
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