Just 1,500 light-years from our planet, a stone’s throw on the cosmic distance scale, a team of astronomers could have discovered the nearest black hole to the earth. Is named Gaia BH1 and its mass has been estimated at ten times that of the Sun.
By definition, and not emitting any light, the black hole in question cannot be seen directly, but the data from the Gaia European Space Telescope They speak out, and have revealed the ‘gravitational pull’ that the obscure object exerts on its orbiting companion star, which is similar, in terms of age and mass, to our own Sun.
Other investigations had already found candidates for nearby black holes, but none of them have been confirmed so far. However, Kareem El-Badry of the Harvard-Smithsonian Center for Astrophysics in Massachusetts and first author of a paper just published in arXiv, is convinced that her discovery is the best candidate so far. The team is so sure that Tsvei Mazeh, one of its members, has not hesitated to say that he is willing to “bet my life on it”.
Normally, for scientists to discover it, a black hole has to be doing ‘something’ that gives it away, be it devouring its companion star if it is part of a binary system, which makes it shine brightly in the range of rays X, either merge with another black hole, causing a surge of gravitational waves that can be picked up from Earth.
But dormant black holes, such as Gaia BH1, are much more difficult to detect, because they are virtually invisible. These black holes are usually far from any food source, so they remain ‘quiet’ and give no clues about their presence. In the case of Gaia BH1, the star that orbits it is about the same distance as Earth is from the Sun.
The researchers are not clear how this system could have formed. One possibility is that the black hole was originally a much more massive star that expanded to become a red supergiant and then collapsed, perhaps exploding as a supernova, though in that case its companion star is unlikely to survive. Another possible scenario is that the black hole is actually not just one, but two closely orbiting each other, implying that it was originally a three-star system. Finally, there is also the possibility that the companion star was captured by the black hole while passing close to it.
As bright as Jupiter
Now, El-Badry hopes to find out the truth by carrying out a series of follow-up observations with other telescopes, looking for evidence of a binary black hole or even planets orbiting the star, which could suggest there was no such thing. explosive event. “Definitely,” he says, “that star could have planets. If you lived on a planet around the star, the black hole would look as bright as Jupiter, since it’s ‘eating’ a small amount of the star’s solar wind.”
It is believed that there could be tens of thousands of black holes like this in our galaxy, and astronomers hope that Gaia will be able to locate a good number of them in the future. Systems like Gaia BH1 are, in fact, one of the mission targets. According to Lukasz Wyrzykowski of the University of Warsaw, now, with a black hole so close to Earth, “we can think of studying it directly. We don’t normally have opportunities to study these extremes of physics.”