But the latest discovery described a "monster" black hole, heads turned across the astronomy and cosmology communities.
Until now, scientists estimated the mass of a stellar black hole in our galaxy could be no more than 20 times that of the sun.
Yet researchers at the Chinese Academy of Sciences have discovered a stellar black hole with a mass 70 times greater than the sun, according to a release from the American Association for the Advancement of Science (AAAS). Their work is published in the journal Nature.
"Black holes of such mass should not even exist in our Galaxy, according to most of the current models of stellar evolution," said researcher Liu Jifeng of the National Astronomical Observatory of China of the Chinese Academy of Sciences.
This new black hole is located 15 thousand light-years away from Earth and has been named LB-1.
Until a few years ago, stellar black stars could only be discovered when they sucked up gas from a companion star, creating a powerful and detectable X-ray emission.
A new method used by Jifeng and his team searches for stars orbiting an invisible object, being pulled by gravity.
Using the world's two largest optical telescopes, they discovered a star eight times heavier than the sun orbiting around this "monster" black hole every 79 days.
"We thought that very massive stars with the chemical composition typical of our Galaxy must shed most of their gas in powerful stellar winds, as they approach the end of their life," said Jifeng. "Therefore, they should not leave behind such a massive remnant. LB-1 is twice as massive as what we thought possible. Now theorists will have to take up the challenge of explaining its formation."
The study provided several theories as to the formation of this massive stellar black hole. It proposed this could be two smaller black holes orbiting each other, or even a fallback supernova — an exploding star that emits material falling back into itself, forming a black hole.
While LB-1 isn't the largest black hole ever discovered, this may be the largest of its kind that we've detected.