Scientists have discovered in space an atypical collision of black holes

(ORDO NEWS) — Scientists fixed ripples in space-time caused by the collision of two black holes, and received a lot of new information about these objects. Black hole mergers usually occur in double black hole, where both holes move towards each other in a spiral.

However, of the approximately 90 such mergers discovered so far, one stands out as highly idiosyncratic. Discovered in May 2019, the object GW19052 emitted space-time fluctuations unlike any other.

“Its morphology and explosion-like structure are very different from previous observations. The object GW190521 was originally thought to be a merger of two rapidly rotating heavy black holes approaching each other in near-circular orbits, but its features led us to suggest other possible interpretations,” Rossella Gamba, astrophysicist at the University of Jena in Germany.

In particular, it was difficult to explain the short and abrupt duration of the gravitational wave signal. As a result of the merger of black holes, a huge amount of energy is always released in the form of gravitational waves – like ripples from a stone thrown into a pond. But gravitational waves (albeit weaker) must also be generated as the two black holes spiral inexorably.

“The shape and brevity (less than one-tenth of a second) of the signal associated with this particular merger lead us to hypothesize an instantaneous merger of two black holes that occurred in the absence of a helical phase,” explains astronomer Alessandro Nagar of the National Institute of Nuclear Physics in Italy.

There are several ways to get a pair of such gravitationally interacting black holes. First, they could be nearby, formed from small stars from the same piece of a molecular cloud in space.

Another version suggests that two such objects passed close enough to each other to gravitationally “hook” in the so-called dynamic collision. This, according to Gamba and her colleagues, could happen to GW190521.

The scientists developed simulations to test their hypothesis. They simulated the collision of black holes, changing parameters such as trajectory, rotation and mass to try to reproduce the strange gravitational wave signal discovered in 2019.

Their results show that the two black holes didn’t start out as double black holes, but fell into each other’s gravitational web, traversing an incredible eccentric loop before colliding with each other to form one large black hole. And none of the black holes in this scenario rotated.

“By developing accurate models using state-of-the-art analytical techniques and numerical simulations, we found that the highly eccentric merger in this case explains the observation better than any other hypothesis put forward previously. The probability of error is 1:4300,” Matteo Breschi, astronomer at the University of Jena.

The team notes that such a scenario is entirely possible in a “densely populated” region of space, such as a star cluster, where similar gravitational interactions are more likely. These findings are consistent with previous findings about GW190521. The mass of one of the black holes in the merger is about 85 times the mass of the Sun.

According to current models, black holes with a mass greater than 65 solar masses cannot form from a single star, and the only way to form such objects is the merger of two black holes with a smaller mass.

Dynamic collisions between black holes are considered quite rare, and the gravitational wave data collected to date confirm this. However, rare does not mean impossible: the new work suggests that GW190521 may be the first such object in a series of future discoveries.


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