Astronomers may have observed light for the first time as a result of the fusion of two black holes. It would be the first direct observation of the consequences of such a collision and further confirmation for young gravitational wave astronomy, as the California Institute of Technology (Caltech) explains. Because the event christened GW190521g was first observed with the detectors Ligo and Virgo on May 21, 2019, only later the apparently associated light signals were discovered by the Zwicky Transient Facility (ZTF).
Traces of a huge collision
The scientific study was led by Caltech astronomer Matthew Graham, that classifies the discovery. Black holes are particularly difficult to observe directly because light cannot escape their immense gravity. Indirectly, however, can certainly be researched, for example because they accelerate and heat matter in its environment so strongly that it lights up. Under the right conditions, the collision of two black holes could be observed directly, at least according to the theories.
To do this, two black holes would have to merge, which are located in the gigantic material disk around another, much larger black hole. After the collision, they would change direction and then plow through the material gathered there, according to Graham. That would light up relatively briefly – days or weeks – after the collision and that is exactly what has now been observed. Because the ZTF instrument saw on the sky region from which the gravitational waves did not come directly signals, but days later such traces of light were suddenly discovered.
However, the traces were only subsequently discovered in the records. So you could understand that they weakened for about a month and finally disappeared. However, the astronomers were no longer able to analyze the spectrum of the signals and more accurately narrow down their origin. But even so, alternative explanations are largely excluded. The researchers also found that the distant black hole had behaved relatively normally in the 15 years before, without such flashes of light.
Further flashes predicted
If their theory about the light signal is correct, the newly created black hole would have to race into the dust disk around the large black hole again, the researchers say. Then such a flash should occur again that should be visible to the ZTF instrument. It would be another confirmation of gravitational wave astronomy, which is probably the revolution in astronomy that it had long been classified as.
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