About ten billions of light years from the earth, two black holes collided by turning at a speed almost defying astrophysics based on general relativity. The result, a celestial object 225 times more massive than our sun.
“We know that this is a big news when all the areas of astrophysics speak about it,” said Marine Prunier, doctoral student in astrophysics at the University of Montreal, who has already worked with the data from the Laser Interferometal-Wave Observatory (Ligo).
The two black holes made a complete rotation 50 times per second, which is equivalent to 400,000 times the speed of rotation of the earth. “It would be black holes that turn to the limit of what they should according to the theory of general relativity,” explains the astrophysicist. A rare phenomenon since black holes run slowly, especially before a fusion.
The strength of the cosmic event has created a distortion in space-time causing a gravitational wave capable of going to the instruments of astrophysicists. “The very massive objects will distort space-time and make as small waves,” explains Olivier Hernandez, astrophysicist and director of the planetarium.
It is a wave in the form of a signal of barely a tenth of a second which then alerted astrophysicists of two observatories of gravitational waves in the United States. With its scientific name GW231123, the signal reached in November 2023 the Ligo located in Louisiana and California. It is also an international collaboration which has enabled the analysis of the data provided by the American observatories. The Ligo-Virgo-Kagra (LVK) consortium bringing together observatories in the United States, Italy and Japan announced the discovery on Monday as part of the International Conference on General Relativity and Gravitation.
Intermediate black holes (between stellar and supermassif), we detect very little, or not
“Intermediate” black holes
The surprising element of this announcement is the imposing mass of black holes, each being more than 100 times the mass of the sun, raises Marine Prunier. The black holes detected by LVK are generally “stellar”, not exceeding 60 solar masses. “A duty star is not supposed to leave a black hole of this size,” adds the doctoral student. According to the theory of stellar evolution, a too massive star has too much energy to collapse on itself and create a black hole. Which raises the question: how did these two so -called “intermediate” black holes appear?
A fusion of such important celestial objects suggests researchers that the two were also born from an old collision. In other words, four black holes that have become one, a possible index on the formation of supermassive black holes.
Marine Prunier thinks that the two celestial objects observed just before their collision may hide the response at the origin of the supermassive black holes: “Intermediate black holes (between stellar and supermassive), we detect very little, if not. We think they are the “seeds” for the supermassive black holes that we detect in the center of the galaxies. »»
To date, around 300 similar astronomical phenomena have been detected thanks to gravitational waves, but only ten could be confirmed, according to Olivier Hernandez. The power of it broke all the records with an energy released about 15 times that of our sun. The last record was held by a collision detected in 2019 which had given birth to a black hole of a mass equal to 140 times that of the sun.
Smaller detection than a atom
If more than a year has passed between signal detection and the announcement of the collision, “it is not because it is slow or lazy,” said Alan Weinstein, a physics professor at the California Institute of Technology, who has been working with Ligo observatories for more than 25 years.
To reach the scientific announcement, the GW231123 signal was analyzed by at least 500 scientists, according to the professor. “Gravitational waves are a recent area. So we have to pay very attention to the mistakes, ”he explains.
Gravitational waves are detected by huge laboratories which measure a distance between 3 and 4 km in an extremely precise way. When space-time is modified by a cosmic phenomenon, the caused wave varies the measured distance. “The size of this distortion is as small as that of an atom,” says doctoral student Marine Prunier.
Visible noise on the data can be caused by human vibrations, maintains Mr. Weinstein. Scientists therefore take the time to check, based on the theory of general relativity of Einstein, that they are not false alarms, which explains the expectation between detection and publication.
The researcher claims that several other announcements in the world of astrophysics will come in the coming months. “Lots of data is being analyzed. There are other very interesting phenomena that will be published, but it is certain that it is really unusual, ”he adds.