LB-1's 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 a black hole, formed by another physical mechanism.

"This discovery forces us to re-examine our models of how stellar-mass black holes form", said Prof.

But researchers believed that typical stars in the Milky Way shed most of their gas through stellar winds, preventing the emergence of a black hole the size of LB-1, Liu said.

The stellar black hole, LB-1, was discovered by Chinese astronomers and would have a mass 70 times greater than our sun, according to a press release from the Chinese Academy of Sciences. "Therefore, they should not leave behind such a massive remnant", he explained.

The direct sighting of LB-1 proves that this population of over-massive stellar black holes exists even in our own backyard.

The study suggests some potential explanations, including the "exciting possibility" that LB-1 might actually consist of two black holes orbiting each other, though Bregman said that would be rare.

Until just a few years ago, stellar black holes could only be discovered when they gobbled up gas from a companion star.

Scientists occupy stumbled on a "monster black hole" so huge that, in theory, it must no longer exist.

An artist's impression of the LB-1 black hole, recently discovered by Chinese scientists.YU Jingchuan, Beijing Planetarium, 2019.

But Liu Jifeng, a professor at the National Astronomical Observatory of China who led the team that made the discovery, said that LB-1, under this theory, was too big to exist.

It is believed that stellar black holes are commonly dispersed throughout the universe, but they are hard to detect because they normally do not emit X-rays, they only do so when they engulf gas from a star that has ventured close enough.

The L1-B is one of the larger ones discovered.

Our private galaxy, the Milky Intention, has a supermassive sunless hole within the middle that has a mass of about 4 million suns. Theorists now want to take up the challenge of finding out how did it form.

Stellar black holes are believed to be commonly scattered across the universe, but they are hard to detect because they do not normally emit X-rays - only doing so when they gobble up gas from a star that has ventured close enough.

The new study was published online Wednesday (Nov. 27) in the journal Nature. Instead of looking for X-rays emitted by black holes, the team searched for stars that orbited some invisible object, attracted by its gravity.

According to the Chinese astronomers who discovered LB-1, it is possible that the very big black hole was not formed from the collapse of one star, but could be a result of two smaller black holes orbiting each other in proximity.

This computer-simulated image shows a supermassive black hole at the core of a galaxy.

Out of the 100 million black holes believed to exist in our galaxy, Liu said, only 4,000 "can give you X-rays that can be detected by us".