When astronomers say that something “shouldn’t exist,” it seems like the universe has a habit of taking it for a challenge. Black hole physicists calculated that there is a range of stars whose mass is so great that it would be impossible for them to form black holes at the end of their lives; instead they should violently explode in a “pair-instability supernova.” That impossible mass range is between 55 and 130 solar masses, with one solar mass being the mass of our sun. Some physicists were so confident that a black hole this heavy could never exist, a a bet for a $100 dollar bottle of wine was made in 2017. Now it looks like someone might have to pay up, because the LIGO and Virgo gravitational wave detectors may have just detected one of these impossible black holes.
“May have,” because although the astrophysics community is awash in rumors of an impossible black hole, the people who have the data won’t confirm it. Natalie Wolchover, senior editor of Quanta magazine, writes:
Seven experts contacted by Quanta said they’d heard that among the 22 flurries of gravitational waves detected by LIGO and Virgo since April, one of the signals came from a collision involving a black hole of unanticipated heft — purportedly as heavy as 100 suns. LIGO/Virgo team members would neither confirm nor deny the rumored detection.
I wouldn’t put it past a bunch of space-nerds to take a $100 bottle of wine so seriously. They did write up a contract, after all. But the lack of confirmation certainly has nothing to do with that; likely it’s that when you think you’ve detected something impossible you want to make sure you’ve gotten it right before putting your name on it.
So just how impossible is this black hole? When asked about how many black holes were predicted to exist in this mass range, Stan Woosley, an astrophysicist at the University of California, Santa Cruz said:
“The prediction is no black holes, not even a few. But of course we know nature often finds a way.”
The “pair-instability mass gap” of black holes refers to the 55-130 solar mass range, where instead of forming black holes as they collapse, stars explode. As the stars collapse, their core grows so hot that light spontaneously converts to electron and positron pairs (which are oppositely charged versions of the same subatomic particle and thus destroy each other). This causes a runaway explosion that annihilates the star in a matter of seconds—a “pair-instability supernova.”
Black holes can theoretically also form at solar masses of above 130, as the immense gravity is so strong that not even a supernova can escape, but monstrous stars big enough to create one of those are exceedingly rare. We’re not going to talk about the million- and billion-solar-mass supermassive black holes that hold galaxies together at their centers. No one knows how those things happen.
But still, a black hole that measures 100 times the mass of our sun is pretty big; and the math that says it’s impossible Yet there are always contrarians, and a few scientists predicted that there may be other means for a black hole in this mass range to form. This disagreement led to a bet being made at a 2017 meeting at the Aspen Center for Physics, stating that no black hole between 55 and 130 solar masses would be found in the first 100 signals detected by LIGO and Virgo. And while it hasn’t yet been confirmed, there’s still a valuable lesson here: if you bet that nature won’t do the seemingly impossible, you’ll probably have to pay up.