Production: Pablo Cantudo
On September 2, a news item with great impact in the media was made public: the most massive detection with gravitational waves of the collision of two black holes; that is, the largest black hole detected with gravitational waves. What impact does this finding have on science? Will physics books be rewritten?
Let’s start with the basics: gravitational waves are disturbances in the fabric of space-time, which are produced as the result of a very massive collision, for example, between neutron stars or between black holes: like when you throw a stone into a lake that creates waves that spread across the entire surface. These disturbances reach the Earth and, although we do not notice them, but they can be captured by scientists.
Gravitational waves were described by Einstein over a hundred years ago, in his Theory of Relativity; but it was not until 2016 that we were able to detect them in practice with our instruments. The LIGO and Virgo observatories are dedicated to this task. To date, around a dozen gravitational wave detections have been made, coming from colliding black holes, or neutron stars. So what makes this detection so special?
The detection has occurred from the merger of two black holes of masses much greater than we are used to capturing. A black hole is a cosmic object with such gravity that nothing can escape from it, not even light. And there are two types: black holes with masses less than 60 times the mass of our Sun, which are supposed to have been formed by very massive stars that died and their gravity made them collapse on themselves; and supermassive black holes, of more than 1000 solar masses.
All the detections of gravitational waves have always been produced from the collision of stellar black holes, of less than 60 solar masses; Except this one that has been starred by a 66 solar mass black hole, and another 85, resulting in a 142 solar mass black hole. Let’s say it is a mass range that physics did not contemplate.
For this reason, some media have stressed that it was a detection that should not exist, or that scientists do not know how it happened. But there are ways to explain this detection, without having to disprove Einstein or rewrite the physics books. One possibility is that stellar physics needs to be revised or tweaked; and the second possibility is that the two black holes that collided in turn are the result of other collisions of smaller stellar black holes.
The latter is the most likely option according to Alicia Sintes and Sascha Husa, two researchers from the LIGO project in Spain, who we had the opportunity to interview here.
