Gravity observatories observed the black hole being eaten by a neutron star
In January 2020, ten days in a row, gravitational observatories first (and second) detected gravitational waves that were stirred up by an extreme gourmet experience – the swallowing of a neutron star through a black hole. We have not yet reliably observed something like this. For gravitational astronomers, this is another historic achievement.
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Eating a neutron star. Credit: NSHB.
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Gravitational astronomers have acquired a great scalp. For the first time, they were able to reliably detect gravitational waves that stirred up a remarkable extreme event during which a black hole ate a neutron star. In fact, there were two such events. Gravitational observatories picked up one signal of this kind on 5 January 2020 and the other 10 days later, on 15 January 2020. Similar gravitational waves have been observed before. However, these signals are the first (and second) of its kind to be officially confirmed.
Vivien Raymond. Kredit: Cardiff University.
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Gravity observatories have previously detected cataclysmic collisions of two black holes, as well as two neutron stars. According to Vivien Raymond, a member of the LIGO observatory team from the Gravity Exploration Institute at Cardiff University in Ireland, this is exactly what they lacked in the puzzle – the collision of a black hole with a neutron star. Now we have a picture of extreme precipitation complete, at least in terms of known objects.
The first of these two events is called GW200105. Researchers are convinced that we have witnessed an ancient fusion of a black hole with a mass of about 9 Suns with a neutron star, the mass of which corresponded to 1.9 Suns. This signal was actually detected by only two workplaces, LIGO Livingston and Virgo. The second site of the LIGO Observatory, or LIGO Hanford, was out of service at the time. Nevertheless, this signal was strong enough to be reliably acknowledged. Researchers have calculated that in this case, a black hole ate a neutron star 900 million light-years away. At the same time, unfortunately, they were not able to determine more precisely from which area of space the signal came.
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The western arm of the Virgo Observatory. Credit: Jérôme Degallaix / Wikimedia Commons.
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The second of the events, designated GW200115, took place about 1 billion light-years away. A black hole with a mass of 6 Suns saw a neutron star weighing 1.5 Suns there. This time, the gravitational waves captured all the mentioned workplaces, so it was possible to narrow the area of the sky where this signal comes from to an area of about 3,000 full moons.
Unlike the now legendary collision detection of two neutron stars in 2017, classic telescopes this time did not detect any electromagnetic radiation that we could associate with the events GW200105 and GW200115. Explanations may vary. These are distant events, and their eventual light show may have been too faint for us to detect. Another possibility is that the black hole simply swallowed the neutron star and did not choke anything. When two neutron stars collide, it’s different. There will be a spectacular explosion.
Video: Neutron star-black hole merger
Literature
Astrophysical Journal Letters 915: L5.
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