Gravitational wave data reveals new insights into black hole behaviour
A decade’s worth of gravitational data has revealed some explosive insights, some that could only be theorised up to this point, about the universe’s mysterious black holes.
Australian astrophysicists have teamed with hundreds of scientists across the globe to chart the behaviours of some of the universe’s most mysterious objects in a groundbreaking study.
Analysis of new gravitational wave data, led by researcher Christian Adamcewicz – from Monash University and the ARC Centre of Excellence for Gravitational Wave Discovery – has mapped out some of the most intense, violent events in our universe to uncover clues about the lives and deaths of stars.
Their analysis provides a foundational understanding of the universe that could only be theorised up to this point
Gravitational waves are ripples in space time caused by high-speed movements of astronomical objects, including the asymmetric explosion of a star, called a supernova, or when two black holes orbit each other and merge, according to NASA.
Mr Adamcewicz said the rate of black-hole mergers dropped off at about 40 times the mass of the sun, but evidence as to why they decreased in this range had mostly remained a mystery.
“We’ve had this hypothesis for a while that really heavy stars – 40 times heavier than the sun – instead of collapsing down to black holes, like you would normally expect, undergo a process called pair-instability supernova,” he said.
“It produces an explosion in the star that is really violent and just blows the whole thing apart, so there’s nothing left to collapse into a black hole. (It is) so explosive that any evidence of (the supernovas) is annihilated.
“We’d never seen clear evidence for that previously, but this newly discovered drop off in our observations matches that prediction really well.”
Mr Adamcewicz said another major insight came from understanding the environments from which some black holes formed.
“For the first time, we’re seeing really confident evidence that a significant portion of these black hole mergers have misaligned spins,” he said.
“This is basically considered smoking-gun evidence that a big fraction of the binary black holes we’re seeing are forming and merging in dense, chaotic environments as opposed to calm, isolated areas of space.
“We may be able to use (this insight) to get a better idea of what goes on in these sorts of environments, as they’re currently not well understood.”
Observatories LIGO, Virgo and KAGRA, based in the US, Italy and Japan respectively, lead a transnational collaboration to produce, compile and release the gravitational wave data catalogue for scientists around the world to analyse following observing periods.
The existence of gravitational waves, first theorised by Albert Einstein in 1915, was proved in 2015 by the observation of waves that resulted from merging black holes approximately 1.3 billion light years away.
Mr Adamcewicz said that in the decade of studying the gravitational waves since their discovery, more than 200 events had been detected.
“That’s unprecedented, getting that many of these observations to look at,” he said. “With other methods, it’s usually kind of on the order of a few dozen, and part of that is just due to the kind of amount of space that we’re able to see.
“These detectors are sensitive to something like on the order of billions of light years away, which is kind of a huge amount of volume that we’re able to look at and observe.”
