A black hole that is 70 times the mass of our star. It’s incredibly heavy! Something like that is impossible to exist, at least according to current theories. How is it possible?
It is estimated that the Milky Way contains 100 million stellar black holes, but the one just discovered by an international team of astronomers led by the National Astronomical Observatory of China, breaks all the schemes. The black hole found in our galaxy is so large that it challenges existing models of how stars evolve. It is located about 13,800 light years away from us, in the constellation Gemini.
By theory, black holes in our galaxy that form from the explosive deaths of massive stars, as this one likely did, shouldn’t weigh more than about 25 suns.
Unique
However, the black hole, which has been dubbed LB-1, has a mass 70 times that of the Sun. The large mass of LB-1 falls into a range known as a ‘pair instability gap’, something that only it can occur in extremely massive stars. Supernovae are not supposed to have produced it (stars large enough to form a black hole like this should be destroyed by supernova explosions, not leaving a black hole in their place), leading experts to believe that it might be try a new type of black hole, formed by another physical mechanism. LB-1 is twice as massive as scientists believed possible, said Liu Jifeng, a professor at the China National Astronomical Observatory who led the research.
How many types of black holes are there?
Supermassive black hole, medium black hole, stellar black hole, and micro black hole, depending on their mass.
“LB-1 is twice as massive as we thought possible . Now theorists will have to take on the challenge of explaining its formation,” the expert clarifies.
How was it detected?
Black holes, unless they are actively accumulating matter – which then does glow at various wavelengths throughout the spectrum – are literally invisible. They do not emit any radiation that we can detect ; therefore, without light, without radio waves, without X-rays … how can we detect it? Not being able to observe it does not mean that we do not have detection tools that infer its presence.
The radial velocity method is used as one of the main ways to search for and confirm the existence of difficult-to-see exoplanets, as they exert a small gravitational influence on their stars. And, logically, we can also use this procedure to find other invisible objects, such as a black hole.
Thanks to the combination of the Large Sky Area Multiple Object Fiber Spectroscopic Telescope (LAMOST) in China, the powerful Gran Telescopio Canarias in Spain and the Keck Observatory in the United States, scientists discovered the incredible object they had found. Looking for stars that orbit an invisible object, dragged by its gravity, only a black hole and a huge one fit the description , according to their study published in the journal Nature.
The star, about 35 million years old and with a speed of eight times the mass of the Sun, is orbiting the black hole every 79 days in what the researchers called a “surprisingly circular” orbit.
It is clear that LB-1 has suddenly become one of the most interesting objects in the Milky Way , and it is likely that, from now on, multiple follow-up observations of this gigantic and particular black hole will be made.
Referencia: Jifeng Liu et al. ‘A wide star-black-hole binary system from radial-velocity measurements’, Nature, November 2019. DOI: 10.1038/s41586-019-1766-2
