Gravitational wave detectors measure signals that indicate two cosmic disasters: Black holes have engulfed neutron stars.
FRANKFURT/HANOVER – If large masses in the universe accelerate, then gravitational waves are produced – a phenomenon predicted by Albert Einstein more than 100 years ago but only confirmed in 2016 when the first gravitational waves were detected. was measured. Meanwhile, gravitational waves have been measured several times by the special detectors LIGO and Virgo, but now a scientific publication shows a measurement that is unparalleled to date: within a few days, the gravitational waves of two cosmic disasters reached detectors on Earth .
The LIGO and Virgo detectors detected gravitational waves in early January 2020; The study on this was not published until the end of June 2021 im Fachjournal “Astrophysical Journal Letters”. The researchers, some of whom are employed at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Potsdam and Hanover, and the Leibniz University of Hanover, are no doubt involved. January 2020, in his opinion, was clearly black. Holes devouring neutron stars.
Gravitational wave phenomenon GW200105: Black hole swallows neutron star
The first gravitational wave event measured on January 5, 2020, was named GW200105. According to scientists, the signal comes from a black hole nine times the mass of our Sun. This black hole merged with a compact object 1.9 times the mass of the Sun, about 900 million light-years away. Experts believe that the lighter object is a neutron star.
“The sign exceeds all our strict quality controls,” emphasized Harald Pfeiffer of AEI Potsdam in a message to the institute. However, since the signal was only observed with one of three available detectors, the origin of the gravitational waves could only be confined to about 17 percent of the entire sky.
Gravitational wave phenomenon GW200115: Black hole merges with neutron star
Just ten days after the first signal, gravitational wave detectors found another sign of a giant merger. In the case of the GW200115 event, a black hole with six solar masses and a neutron star with 1.5 solar masses was involved, and the merger took place about a billion light-years away from Earth. Since in this case all three detectors (the two LIGO detectors and the Virgo detector) saw the signal, science can pin down the origin of the gravitational waves a bit more precisely – however, a larger region of the sky is still possible.
Gravitational waves: Black holes completely devour neutron stars
Apart from the measured gravitational waves, no further signs of the event could be detected, with subsequent observations from several observatories finding no signal in the electromagnetic spectrum. But it doesn’t come as a surprise to experts in Hannover: “Observation of the electromagnetic signal from the merger would have been spectacular, but we didn’t expect it,” says Frank Ohme from AEI. Ohme explains that due to the large distance and precise positioning, the light would be very weak and very difficult to detect. “We also conclude from the data that the black holes involved in these mergers swallowed their neutron star partners in one piece, so that no light was emitted.”
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But how do scientists know that it was the neutron stars that were swallowed by the black hole? “Gravity waves alone do not tell us the composition of the lighter object, but we can estimate its maximum mass. Combining this information with theoretical predictions about the expected mass of neutron stars in such a binary system, we can conclude that But a neutron star is the most likely explanation,” explains AEI’s Bhushan Gadre in a press release from the institute.
Black hole merger with neutron stars causes gravitational wave
Researchers are sure they have observed gravitational waves from merging black holes with neutron stars for the first time. They recognize that such events are not rare: at distances of up to a billion light years, they expect such mergers per month – but not all of these events can be detected with current detectors.
Exactly how double systems arise from black holes and neutron stars has not yet been elucidated. Astronomers consider this a possible explanation that binary stars may have evolved in such systems. But such dual systems can also have origins around the centers of young star clusters or galaxies.
The gravitational wave detectors are scheduled to run their fourth observation in the summer of 2022. “They will then become even more sensitive, so that we can observe gravitational waves every day,” says AEI’s Carsten Denzmann happily. “In a few years, we will see more black holes merging with neutron stars. This will allow us to learn more about matter under extreme conditions, the life of stars, and the properties of these rare events.” (tab)
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