The recent detection of a gravitational wave showing the collision of two black holes that occurred some seven billion years ago, before the formation of the solar system, is transcendent for fundamental science, because it provides scientists with new clues about the origin of the stars, warned William Lee Alardín, coordinator of Scientific Research at UNAM.
The also researcher at the Institute of Astronomy explained that this event is another record of the recent gravitational wave observatories: the LIGO detector, from the United States, and the Virgo, from Italy.
“The finding is important because it allows us to observe the Universe in a different way , in a complementary way to the light that comes to us from all the objects we know. Gravitational waves, like the one that was captured, are small tremors in space-time , as if they were small stones on the surface of a pond or disturbances in an elastic membrane that is stopped at the corners and trembles when throwing a ball. ”, He explained.
LIGO has been five years since they made the first detection, which was also a collision of two black holes, which earned the team the Nobel Prize in Physics.
In 2015 the first direct detection of the collision of two black holes occurred, and since then this class of objects has been recorded.
“These vibrations of space-time allow us to know that something far away, and a long time ago, collided or exploded. Gravitational waves tell us that a lot of mass moved very quickly. They are a prediction of Einstein’s theory from 105 years ago and they tell us about objects that explode, and do things at enormous distances: they are born, die or make violent movements ”, he explained.
He explained that the detections made until now had been black holes between eight and 50 times the mass of the sun.
“There have always been two, and from the signal you can measure the mass of each of them. In these mergers of pairs a black hole of up to 85 solar masses was formed ”, he pointed out.
The astronomer explained that black holes of a few dozen solar masses come from the death of massive stars, which at that time produce a supernova explosion; if it is very light, a neutron star is formed. However, if it is more massive, it forms black holes that can have several tens of solar masses.
“The difference between this event and the previous ones is that the black holes involved are much more massive. The lightest weighs 65 times the mass of the Sun and the most massive 85 . When they collided, they resulted in an object of about 142 solar masses; the rest is radiated as energy in waves during the collision, “he said.
Astronomers thought that when the most massive stars die they no longer produce black holes , because when they explode they completely destroy the star, there is no trace left. That threshold is about 65 times the mass of the Sun.
“And in this event we see holes of 65 and 85 solar masses, that’s why it is important. The event is beyond, in the masses of the components, what we knew was possible for its origin ”, she specified.
One likely explanation, William Lee noted, is that astronomers did not fully understand stellar evolution. Another possibility is that each of these holes with these masses was formed not by the explosion caused by the death of a star, but by a process called hierarchical formation.
“To form the 85-solar-mass black hole, perhaps a 40-mass and a 45-mass black hole came together a long time ago; they made this one of 85, which is now joined with the one of 65. This is called hierarchical formation and a giant black hole is formed from several smaller ones ”.
The astronomer stressed that this finding is important because the mass range presented by this object had not been detected and it is not known how it was formed, “it is a good example of how gravitational waves present us with new objects that we had not seen.”