It is a door that opens to a new cosmic landscape. A whole new world! “Stavros Katsanivas, at a press conference, welcomed the director of Virgo, one of the two gravitational wave detectors who had captured the signals of this new black hole.

This is the first direct evidence of black holes of medium mass (between 100 and 100,000 times larger than the Sun), which could explain one of the mysteries of cosmology: the formation of supermassive black holes. These cosmic monsters lurk in the center of some galaxies, including the Milky Way.

The mysterious object, described in Physical Review Letters and Astrophysical Journal Letters by an international team of more than 1,500 scientists, is called “GW190521”. Most likely from the merger of two black holes, the Sun is 142 times the mass of the Sun and forms the largest black hole ever detected by gravitational waves (the massive mass, billions of times larger, was detected otherwise).

Predicted by Albert Einstein in 1915 in his theory of general relativity and observed directly after a century, gravitational waves are small distortions in spacetime, similar to ripples of water on the surface of a pool. They were born under the influence of violent cosmic phenomena, such as the collision of two black holes, which released an enormous amount of energy.

The gravitational wave GW190521 took 7 billion years to reach us: it is the most distant black hole, and thus the oldest ever discovered.

A primitive black hole?

The signal was recorded on May 21, 2019 by the American Ligo and European Virgo machines, which have signed their “biggest catch at their fishing table” since their first discoveries in 2015 and 2017, and CNRS details, which many researchers have contributed to studies.

This signal was very short (a tenth of a second), and its frequency very low (the more back in the past, the lower the frequencies): “a challenge to its analysis,” Nelson Christensen emphasized, for Ligo cooperation.

So far, only indirect evidence, through electromagnetic observations, indicates the existence of this cluster of intermediate black holes.

Heavier than collapsing stars’ black holes, but much lighter than supermassive monsters, they could be “a key to one of the mysteries of astrophysics and cosmology: the origin of supermassive black holes,” according to CNRS. One of the hypotheses explaining the birth of the latter would be, specifically, the frequent merging of intermediate mass black holes.

Another interesting phenomenon: Where did the two black holes that merged come from? According to current theories, a star collapse could not lead to black holes from 60 to 120 times the mass of the sun, which is exactly the size of the two objects that merged. Could there be a primordial black hole that formed during the Big Bang, 13.8 billion years ago? Or are they themselves the result of a merger?

The discovery of GW190521 raises new questions. Astrophysicist Karan Jani, of Ligo, commented that “there is a large part of the universe that has remained invisible to us.”