Just the other month, scientists found what could be the tiniest stellar black hole ever recorded. Now, an international team of astronomers may have discovered another black hole, but one that is so gigantic it actually makes no sense to be there.
The black holes are usually fit into two distinct categories: supermassive black holes, and stellar black holes. The supermassive ones are believed to live at the center of every galaxy, including our Milky Way. These cosmic bodies are exactly how their name is, as they can be more gigantic by millions of tens of billions of times than our Sun.
Stellar black holes are taking shape when a massive star, about 20 times bigger than the Sun, gets to the end of its lifespan. The object then explodes in a supernova, throwing off its outer layers, abandoning about a 4-5 solar mass core, which falls onto itself to create a black hole.
Found Almost by Mistake
The most gigantic stellar black hole discovered in our galaxy until now edges the levels at just a tiny of 15 solar masses. Astronomers decided to set the upper limit of stellar black hole mass at approximately 30 to 40 solar masses.
Now, a team of scientists led by astronomers at the Chinese Academy of Sciences has published a new study in the journal Nature, detailing the finding of LB-1, a cosmic body that could be the most gigantic stellar black hole ever discovered in our galaxy.
“Black holes of such mass should not even exist in our galaxy, according to most of the current models of stellar evolution,” said Professor Liu Jifeng of the National Astronomical Observatory of China.
LB-1 was observed as Liu’s team analyzed a massive blue star, approximately 15,000 light-years away, oscillating around in the background of space. Because of this oscillation, they suggested the best explanation was that the star was rotating around some other cosmic body, every 79 days.
Because they could not identify the star’s mate, that indicated to that body being a quiet black hole that was not generating X-rays as it absorbed matter from its accretion disk. After a series of calculations, the team determined that the companion was massive, weighing almost 70 solar masses. Considering the way massive stars form and die, a black hole this gigantic should not be possible in our galaxy.
As per Liu, the most massive stars in our galaxy usually lose a huge quantity of their mass as they reach the end of their lives because of having incredibly powerful stellar winds. This process is strikingly similar to how our Sun loses mass in a consistent stream through the solar wind, but much more powerful, taking away way more mass in a shorter time frame.
Based on this, they should not be able to shack off a remnant that can fall on itself to form a 70 solar mass black hole.
“LB-1 is twice as massive as what we thought possible,” Liu said. “Now, theorists will have to take up the challenge of explaining its formation.”
There are lots of questions with as many possibilities. Could LB-1 have taken shape from a similar black hole merger before the humanity discovered how to identify gravitational waves? Is rather LB-1 a captured star, having formed in another galaxy, but ended up in ours sometime later in its lifespan? Is there a logical explanation for how such a massive black hole could actually exist?
“This discovery forces us to re-examine our models of how stellar-mass black holes form,” LIGO Director David Reitze, from the University of Florida said.