Transmissions embedded deep in gravitational wave observatories’ data point to a collision involving two black holes that were evidently born in various locations.
Most of the space – time ripples observed by experiments such as the Laser Interferometer Gravitational-Wave Observatory, or LIGO, are caused by collisions between black holes and neutron stars that are most likely close relatives (SN: 1/21/21). They were originally pairs of stars that were created at the same time and in the same place before collapsing to produce circling black holes or neutron stars in old age.
A newly discovered marriage of black holes, discovered in existing data from the US-based LIGO and its Italian sister observatory Virgo, appears to be of an unconnected couple. Researchers claim in a publication in print at Physical Review D that evidence for this comes from just how they spun as they combined into one. Black holes that are created in the same place tend to have their spins aligned, like a pair of toy tops spinning on a table, as they orbit one other. However, there is no link between their respective spins and orbits in this situation, showing that they were born in distinct places.
“This is telling us we’ve finally found a pair of black holes that must come from the non-grow-old-and-die-together channel,”
Seth Olsen, a physicist at Princeton University.
Earlier gravitational wave measurements have revealed holes merging that aren’t exactly aligned, but most are near enough to strongly infer familial links. The latest finding, which Olsen and colleagues discovered by trawling through data made available by the LIGO-Virgo partnership, is distinct. One of the black holes is essentially rotating on its side.
That can’t happen unless the two black holes originate in different places. They most likely met late in their stellar lifetimes, as opposed to the black hole littermates who appear to account for the majority of gravitational wave observations.
In addition to the merging of unrelated black holes, Olsen and his colleagues discovered nine more black hole mergers that had escaped detection in previous LIGO-Virgo experiments (SN: 8/4/21).
“This is actually the nice thing about this type of analysis. We deliver the data in a format that can be used by other people and then [they] will have access to try out new techniques.” stated LIGO scientific collaboration spokesperson Patrick Brady, a physicist at the University of Wisconsin–Milwaukee who was not affiliated with the new study.
Olsen’s group dropped the analytical hurdle somewhat in order to compile so many new signals in data that had already been examined by other researchers.
“Out of the 10 new ones, there are about three of them, statistically, that probably come from noise,” Olsen claims. Instead of becoming conclusive detections of black hole mergers. Considering that the merging of black hole strangers isn’t one of the incorrect signals, it very probably provides a story of black hole histories unique from those witnessed thus far.
“It would be extremely unlikely for this to come from two black holes that have been together for their whole lifespan,” Olsen says. “This must have been a capture. That’s cool because we’re finally able to start probing that region of the black hole population.”
“We don’t understand the theory [of black hole mergers] well enough to be able to confidently predict all of these types of things.” Brady noted. However, a recent research might indicate to new and exciting potential in gravitational wave astronomy. “Let’s follow this clue to see if it really is reflecting something rare,” he says. “Or if not, well, we’ll learn other things.”
Image credits: HENZE/AMES RESEARCH CENTER/NASA
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