Newly-detected gravitational waves are revealing the complex lives of black holes
For millions of years, two incredibly massive stars orbited one another in a distant part of space.
The stars lived their lives circling one another as companions (or possibly frenemies). Eventually, those two stars reached the ends of their lives, collapsing to form two black holes that continued to orbit one another for millions more years.
The two black holes spiraled ever-closer to one another until one day something amazing happened: they merged.
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According to a new study in the journal Nature this week, that may be the most likely scenario for how the two black holes that created the first ripples in space and time detected by humanity came to be.
"The black holes were monsters, and the results show that their progenitor stars would have been some of the brightest and most massive in the universe," physicist J.J. Eldridge, who was unaffiliated with the new study, wrote in a News and Views piece accompanying the study.
In September 2015, scientists using two twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors in Washington and Louisiana got their first glimpse of the tell-tale ripples in space-time that have eluded direct detection by researchers since they were theorized by Albert Einstein about 100 years ago.
Working backwards from ripples in space-time
Einstein hypothesized that when two massive objects like black holes or neutron stars orbit one another and then merge, it can create distortions in space-time -- the literal fabric of the universe -- much like ripples on a pond.
The LIGO detection in 2015 was humanity's first look at those ripples, opening up a new way of investigating mysterious cosmic objects like black holes. Since then, scientists have announced one -- and possibly two -- more detections created by black hole binaries.
And now, researchers are using clues embedded within gravitational wave signals -- plus some nifty simulations of the universe from the Big Bang to now -- to work backwards and figure out exactly how those objects came to be.
"We populate the synthetic universe with all those different stars and you let those stars evolve. As those stars evolved, they produce black holes, neutron stars all sorts of weird objects and then some of them merge and hit each other, and they go, 'bang' in different ways," co-author of the study Krzysztof Belczynski of Warsaw University in Poland, told Mashable in an interview.
How many black hole mergers will we see?
"In our synthetic universe, we are gods, so we know what actually gives rise to those explosions, to those mergers," Belczynski added. "We can go back into our model and see, okay, these types of stars make those black holes. It's most likely that the black hole merger came from that type of star and that cosmic time."
This new study also posits that black hole pairs may be quite common. In fact, there could be hundreds of large black holes merging every year.
Instead of becoming black holes together, it's possible a binary may come to be within a star cluster.
Some scientists think the jury is still out on how these large black holes form in the first place, and LIGO will need to detect a lot more of their mergers before we can say definitively how they come to be.
"If we just wait for more LIGO events -- right now we have two with potentially a third one -- and if we collect, let's say, a few more, then we will have a much better ground for drawing conclusions," astronomer Avi Loeb of the Harvard-Smithsonian Center for Astrophysics, who is unaffiliated with the study, told Mashable in an interview.
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Miriam Kramer worked as a staff writer for Space.com for about 2.5 years before joining Mashable to cover all things outer space. She took a ride in weightlessness on a zero-gravity flight and watched rockets launch to space from places around the United States. Miriam received her Master's degree in science, health and environmental reporting from New York University in 2012, and she originally hails from Knoxville, Tennessee. Follow Miriam on Twitter at @mirikramer.
