Astronomers say they have detected the most massive merger of two black holes ever discovered

Astronomers may have detected the most massive collision of two black holes ever discovered, a chaotic merger that occurred about 7 billion years ago, the signals of which have barely reached us. The cataclysmic event offered researchers a front row seat to the birth of one of the most elusive objects in the Universe.

The distant show featured two main actors: a black hole roughly 66 times the mass of our Sun, and another black hole roughly 85 times the mass of our Sun. The two zoomed in, rapidly spinning around each other several times per second. before finally colliding together in a violent blast of energy that sent shockwaves throughout the Universe. The result of their merger? A single black hole approximately 142 times the mass of our Sun.

Such a finding could be important to astronomers. Until now, scientists have been able to indirectly detect and observe black holes in two different size ranges. The smallest variety is between five and 100 times the mass of our Sun. At the other end of the spectrum are supermassive black holes, the kind at the centers of galaxies that are millions and billions of times the mass of our own. Sun. For centuries, scientists have been trying to locate intermediate black holes, so-called “intermediate mass black holes” ranging from 100 to 1000 times the mass of the Sun. Astronomers were sure this type must be there, but they had not been able to find any direct evidence of its existence. A few possible intermediate black holes have been detected, but are still considered candidates.

“They are really the missing link between [black holes with] tens of solar masses and millions, ”says Salvatore Vitale, an assistant professor at MIT’s LIGO Lab who studies gravitational waves. The edge. “It was always a bit puzzling that people couldn’t find anything in between.”

With this discovery, detailed today in the magazines Physical Review Letters and The Astrophysical Journal Letters, we may have our first detection of the birth of an intermediate mass black hole. The discovery could help explain why the Universe looks the way it does, with relatively abundant scattering of smaller black holes and some supermassive black holes at the centers of galaxies. One theory of how supermassive black holes get so big is that smaller black holes merge over and over again, consolidating until they get huge. But if that were the case, there would have to be intermediate black holes somewhere in the Universe. “That’s why astronomers have been looking for them extensively, because they would help solve this puzzle,” says Vitale.

Image: LIGO / Caltech / MIT / R. Wounded (IPAC)

To detect this dance of black holes, scientists measured the tiny shock waves that the merger produced. When incredibly massive objects like black holes merge, they warp space and time, creating ripples in the fabric of the Universe that shoot outward at the speed of the event’s light. These waves, known as gravitational waves, are gigantic when produced, but when they reach our planet they are incredibly weak and incredibly difficult to detect.

Scientists have become quite adept at detecting these tiny gravitational waves thanks to observatories in the United States and Italy. Known as LIGO and Virgo, the observatories are specifically designed to detect these infinitesimal waves of cataclysmic mergers, measuring how the waves affect mirrors suspended here on Earth. Since LIGO made the first gravitational wave detection in 2015, observatories have amassed an impressive curriculum, detecting approximately 67 black hole mergers, neutron stars, and black holes merging with neutron stars.

At 5.3 billion parsecs away, the detection announced today is also the furthest merger LIGO and Virgo have ever encountered, and it took 7 billion years for the waves to reach us. This event, called GW190521, was detected on May 21, 2019, and was so weak that it could easily have been missed. LIGO and Virgo only picked up four small waves from the merger in their detectors, disturbances that lasted for only a tenth of a second. The scientists working with the data used four different algorithms to find the motions, ultimately allowing them to identify the masses of the fusion and how much energy was released. “During the collision process, the equivalent of seven times the mass of our Sun was destroyed and turned into energy leaving the system, so it’s pretty impressive in terms of energy if you think about it,” says Vitale. “The equivalent of seven suns was destroyed in a very small fraction of a second.”

Due to the small detection, astronomers at LIGO and Virgo are considering the possibility that they may not actually have seen a massive merger of black holes, but instead picked up waves from a collapsing star or some other strange phenomenon. However, the merger of black holes is the simplest explanation and makes the most sense for what they have observed. Astronomers estimate that mergers like this are rarer than the mergers of smaller black holes that LIGO and Virgo have seen, which would explain why observatories have taken a while to detect this type of black hole. “For every event like this, there will be about 500 smaller black hole mergers, so this is very rare,” says Vitale.

But Vitale hopes to see mergers like this again. At this time, LIGO and Virgo are not making observations, but the two facilities will be back online at the end of next year with some updates, making their instruments even more sensitive than before. “We should be able to detect more of this extremely heavy object, and then we can say a little more about its origins, where it came from, how rare it is and its properties,” says Vitale. “So we can really probe the life and death of these black holes.”