Almost a year ago, the Gravitational Wave Detector in the US state of Louisiana detected for the second time signals indicating that black holes may be smaller than previously thought. The Laser Interferometer Gravitational-Wave Observatory (LIGO) has just announced this. The signals were discovered on May 24, 2023, when a neutron star — with 1.4 solar masses — collided with a mysterious object that didn't actually exist. Before the collision, it was about 3.6 solar masses, so it was in the middle of the gap that had been identified for years between supermassive neutron stars and small black holes.
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The space is no longer completely empty
Objects discovered through mass space and gravitational waves
(Article: S. Gallatage, Côte d'Azur Observatory)
As the research institute explains, the signal was detected shortly after the start of the fourth research run of two LIGO detectors, the Virgo detector in Italy and the Gagra in Japan. For various reasons, only one of the two LIGO instruments observed it. A note was immediately released to astronomers, but the data on the possible origin was not very accurate and other instruments could not find anything. So the merger occurred at a distance of about 650 million light years. Research work is currently on hold; A total of 80 additional signals were discovered by mid-January.
The signal, called GW230529, is particularly interesting because it once again points to the solution to an astronomical mystery. This involves the most massive stars collapsing into black holes, while lighter examples explode as supernovae, leaving smaller neutron stars behind. A gap has opened up between the most massive neutron stars of 2 solar masses and the smallest black holes of 5 solar masses, and it is unclear whether there are any smaller objects that can fit there. An object that appears to fall right into this gap has now been detected for the second time using gravitational waves. The first was discovered in 2019, but was very close to the lower limit.
Unlike the previous event known as GW190814, the present one is due to the collision of an object with a small celestial body in the mass interval. Gravitational waves discovered in 2019 are caused by the merger of an object weighing 2.6 solar masses with an object 23 times the mass of our Sun. Another reason why it's “particularly exciting,” explains Silvia Piscovenu, an astrophysicist who was involved in the evaluation. This observation is important for theories of the growth of binary systems and for possible observations in the electromagnetic spectrum. No other black hole was detected in space in 2019 by gravitational waves, so the overall number remains manageable.
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