Astronomers may have detected the largest collision of two black holes ever discovered, about 7 billion years ago, but the signs have only just arrived. The catastrophic event provided researchers with a close-up look at the birth of one of the most elusive objects in the universe. The distant show consists of two main characters: one black hole is about 66 times the mass of our sun and the other is about 85 times the mass of our sun. The two black holes leaned together, rotating rapidly around each other several times per second, eventually colliding in violent bursts of energy, bringing shock waves throughout the universe. The result of their merger is a single black hole about 142 times the mass of our sun.
Such a discovery could be a big one for astronomers. So far, scientists have been able to detect and indirectly observe two black holes of different sizes. Smaller species are between 5 and 100 times the mass of our sun. At the other end of the spectrum is a supermassive black hole, the kind of black hole at the center of a galaxy that is millions and billions of times the mass of our sun. Throughout the ages, scientists have been trying to find black holes in between, the so-called “intermediate mass black holes”, which range in mass from 100 to 1,000 times that of the sun. Astronomers are convinced that such black holes must exist, but have not found any direct evidence of their existence. “It’s always a confusing question that people can’t find any intermediate black holes,” said Salvatore Vitale, an assistant professor at MIT’s LIGO Lab who studies gravitational waves. They are missing links between black holes with dozens of solar mass and black holes with millions of solar mass, and it’s always a bit confusing that people can’t find anything between the two. “
The discovery, detailed today in the journal Physical Review Letters and astrophysical Journal Letters, may be the first time we have discovered the birth of a medium-mass black hole. One theory about how supermassive black holes have become so large is that smaller black holes merge again and again, merging into them. But if that’s the case, there must be an intermediate black hole somewhere in the universe. That’s why astronomers have been looking for these extensively, because they will help solve this problem. To detect this black hole dance, the scientists measured the tiny shock waves produced by the merger. When incredibly large objects like black holes merge, they distort space and time, creating ripples in the fabric of the universe that shoot out of events at the speed of light. These ripples are called gravitational waves and are huge when they are produced, but when they reach our planet, they are very weak and very difficult to detect.
Thanks to observatories in the United States and Italy, scientists are already very good at detecting these tiny gravitational waves. These, known as LIGO and Virgo observatories, are designed to detect these infinite waves from the combined catastrophe. Since LIGO first detected gravitational waves in 2015, the observatory has accumulated impressive results, detecting about 67 black holes, neuter stars, and the merging of black holes with neuter stars. The results, announced today, are also the longest-combined discovery by the LIGO and Virgo observatories, affecting 7 billion years. The incident, called GW190521, was detected on May 21, 2019, and was so weak that it was easy to miss. LiGO and Virgo’s detectors received only four small waves from the merger, which lasted only a tenth of a second. The scientists processed the data using four different algorithms to look for these fluctuations, which eventually allowed them to determine exactly what the mass of the merger was and how much energy was released.