An “impossible” black hole discovered in the Milky Way has shocked scientists and stunned astronomers – as the laws of physics say it is too big to exist.
Using a new search method, the black hole called LB-1 was discovered by an international team of scientists using China’s sophisticated LAMOST telescope. They found a stellar-mass black hole clocking in at around 70 times the mass of the Sun – but according to current models of stellar evolution, its size is impossible, at least in the Milky Way.
LB-1 is 15,000 light-years away from Earth. Its large mass falls into a range known as the ‘pair-instability gap’ where supernovae should not have produced it, leading experts to believe this is a new kind of black hole, formed by another physical mechanism.
The Milky Way is estimated to contain 100 million stellar black holes but LB-1 is twice as massive as anything scientists thought possible, said Liu Jifeng, a National Astronomical Observatory of China professor who led the research.
The chemical composition of our galaxy’s most massive stars suggests that they lose most of their mass at the end of their lives through explosions and powerful stellar winds, before the star’s core collapses into a black hole.
The hefty stars in the mass range that could produce a black hole are expected to end their lives in what is called a pair-instability supernova that completely obliterates the stellar core. So astronomers are scratching their heads trying to figure out how the black hole – named LB-1 – got so chonky.
“Black holes of such mass should not even exist in our galaxy, according to most of the current models of stellar evolution,” said astronomer Jifeng Liu of the National Astronomical Observatory of China. “LB-1 is twice as massive as what we thought possible. Now theorists will have to take up the challenge of explaining its formation.”
Possible theories of its formation
One scenario could be that LB-1 formed from the collision of two black holes and then captured the star later – but the circular orbit of its companion causes a problem here. A capture would produce a highly eccentric, elliptical orbit. Time could smooth this orbit out, but it would take longer than the star’s age.
One possibility, however, could be a fallback supernova, in which material ejected from the dying star falls immediately back into it, resulting in the direct formation of a black hole. This is theoretically possible under certain conditions, but no direct evidence for it currently exists.
However it formed, LB-1 has suddenly become one of the most interesting objects in the Milky Way. Research regarding it has been published in Nature.
Sources: The Sun, Daily Mail, Science Alert
