Officially observed for the first time on September 14, 2015, gravitational waves are disturbances of space-time produced by a massive, accelerating body. usually collisions between black holes or neutron stars. Discovered by scientists at the Interferometer Gravitational Wave Observatory (LIGO), they already appeared in the theory of Einstein relativity, but it was not until a little over five years ago when its existence could be confirmed. Since then, 55 have been ‘heard’, although the LIGO-Virgo-KAGRA collaboration has just released the largest catalog to date: 35 new detections that
increase the number of gravitational waves detected to 90.
Published in the prepress portal ‘
ArXiv‘(that is, it has not yet been peer reviewed) the work is shown with observations ranging between November 2019 and March 2020, using three international detectors: the two LIGO detectors, in the United States, and the advanced Virgo detector, in Italy. The KAGRA detector, in Japan, joined the LIGO-Virgo network in 2020, but was not operational during these latest detections.
Of the 35 events detected, 32 were probably black hole mergers; that is, two black holes that revolve around each other and eventually merge into one, an event that emits a burst of gravitational waves. Among the catalog, its size disparity has drawn attention: the most massive has a mass 90 times that of our Sun. But some of the resulting black holes exceed 100 times the mass of our star, the so-called ‘black holes of intermediate mass’, very ‘elusive’ objects that, despite their size, are being difficult to detect. The fact that this latest catalog has found several means that, as the theory went, they are actually more common in the universe than we thought.
Secondly, 2 of the 35 events detected could be merging neutron stars and black holes, a much rarer event, and one that was only discovered in the last series of observations of LIGO and Virgo. From these rare mergers of neutron stars and black holes, it appears that the result is a massive black hole – about 33 times the mass of our Sun – with a very low-mass neutron star – about 1.17 times the mass of our Sun. -, one of the smallest detected to date.
Also, one of the gravitational wave events in the catalog came from the merger of two objects, one of which was almost certainly a black hole —With a mass of about 24 times that of our Sun—, but the other was a very light black hole or a very heavy neutron star about 2.8 times the mass of our Sun. Scientists have deduced that it is most likely a black hole, but they cannot say for sure.
A similar ambiguous event was discovered by LIGO and Virgo in August 2019. The mass of the lightest object is puzzling, as scientists hope that the most massive a neutron star can be before collapsing to form a black hole is around 2.5 times the mass of our Sun. However, no black hole had been discovered by electromagnetic observations with masses less than about five solar masses. This led scientists to theorize that stars do not collapse to form black holes in this range, but new observations of gravitational waves indicate that these theories would have to be revised.