November 26, 2022


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Two black holes met by chance, creating something never seen before: ScienceAlert

Two black holes met by chance, creating something never seen before: ScienceAlert

Ripples in space-time caused by the collision black holes She taught us a lot about these mysterious things.

these gravitational waves Coding information about black holes: their masses, the shape of the inner spiral toward each other, their spins, and their orientations.

From this, scientists made sure that most of the collisions We’ve seen between black holes in binary systems. The two black holes began as a duo of massive stars that morphed into black holes together, then spiraled out and merged.

Among the 90 or so mergers that have been discovered so farHowever, one stands out as very strange. Discovered in May 2019, GW19052 has emitted space-time waves like no other.

“Its shape and explosion-like structure are very different from previous observations,” says astrophysicist Rossella Gamba from the University of Jena in Germany.

She adds“GW190521 was initially analyzed as a merger of two rapidly spinning massive black holes approaching each other along nearly circular orbits, but its special features prompted us to propose other possible explanations.”

In particular, the Short and sharp affiliate gravitational wave It was difficult to explain the signal.

Gravitational waves are generated by actual merger From two black holes, like ripples from a rock that fell into a pond. But they are also being generated by binary streams, the intense gravitational interaction sending out weaker ripples as two black holes relentlessly approach.

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“The shape and brevity – less than a tenth of a second – of the signal associated with the event leads us to hypothesize an instantaneous merger of two black holes, which occurred in the absence of a spiral phase,” explains astronomer Alessandro Nagar from the National Institute of Nuclear Physics in Italy.

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There’s more than one way to get a pair of black holes to interact gravitationally.

The first is that the two have been together for a long time, perhaps even from the formation of young stars from the same piece of the molecular cloud in space.

The other is when two objects moving through space pass each other close enough to be impeded by their own gravity in what is known as a dynamic encounter.

That’s what Gamba and her colleagues thought might have happened with GW190521, so they designed simulations to test their hypothesis. Together, they smashed pairs of black holes, tweaking parameters like trajectory, spin, and mass, to try to reproduce the strange object. gravitational wave Signal was detected in 2019.

Their findings suggest that the two black holes didn’t start out as a binary but got caught in each other’s gravitational web, rolling one another twice in a wild, whimsical loop before colliding together to form a larger one. Black hole. None of the black holes in this scenario were spinning.

“By developing accurate models using a combination of state-of-the-art analytical methods and numerical simulations, we have found that the eccentric incorporation in this case explains the observation better than any other previously put forward hypothesis.” says astronomer Matteo Bresci from the University of Jena.

“The probability of error is 1:4300!”

The team says this scenario is more likely in a densely populated region of space, such as a star cluster, where such gravitational interactions are more likely.

This tracks with previous discoveries about GW190521. One of the black holes was in the merger It is measured by about 85 times sun block.

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According to our current models, black holes larger than 65 solar masses cannot be formed from a single star; The only way we know Black hole Of this mass they can be formed through mergers between two bodies of less mass.

Gamba and her colleagues’ work found that the masses of the black holes in the collision lie at about 81 and 52 solar masses. This is slightly lower than previous estimates, but one of the black holes is still out of the way of forming a single star core collapse.

It is still not clear whether our models need to be modified, but hierarchical consolidations – where larger structures are formed by the continuous amalgamation of smaller objects – are More likely in a cluster environment With a large number of dense objects.

Dynamic encounters between black holes are very rare, and gravitational wave The data collected by LIGO and Virgo so far seems to support this. However, rare does not mean impossible, and the new work suggests that GW190521 may be the first we discover.

The first of which means there may be more in the coming years. The gravitational wave The observatories are currently being upgraded and maintained but will be online again in March 2023 for a new observation round. This time, KAGRA in Japan will join detectors from LIGO in the United States and the Virgo detector in Italy for even greater observing power.

More discoveries like GW190521 would be amazing.

Research published in natural astronomy.