Evidence of 7 billion-year-old 'biggest yet' merger of two black holes reaches Earth

Astronomers may have detected the most massive collision of two enormous black holes in an intense catastrophe that occurred over seven billion years ago, the signs of which have only just been discovered. On May 21, 2019, the Earth experienced gravitational vibrations set off by this distant collision, guiding the astronomers to the biggest 'cosmic bang' ever detected.

The distant show included two major black holes, one of which was roughly 66 times the mass of our Sun and another that was nearly 85 times the mass of our Sun. The two came close, spinning rapidly around one another several times per second before eventually colliding together in a violent burst of energy. The merger resulted in a single black hole roughly 142 times the mass of our Sun, astronomers have estimated

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This was a significant discovery for astronomers. Up until now, scientists were only able to detect and indirectly observe black holes in two different size ranges. The small ones range between five to 100 times the mass of our Sun. On the other hand, there are some supermassive black holes. Located at the center of galaxies, they are millions and billions of times the mass of our Sun. For ages, scientists have been trying to identify “intermediate black holes” that range between 100 to 1,000 times the mass of the Sun.

With this finding, detailed in the journal Physical Review Letters and The Astrophysical Journal Letters, star-gazers may have detected the first intermediate-mass black hole being born. The discovery could help explain why the Universe consists of numerous scatterings of smaller black holes and a few supermassive black holes at the center of galaxies.

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To detect the merger of small black holes into relatively large ones, scientists measured the tiny shockwaves that the merger produced. When incredibly massive objects like black holes merge, they bend space and time, creating ripples in the Universe that shoot outward at the speed of light from the occurrence. These “gravitational waves” are enormous when produced, but by the time they reach our planet, they become faint and extremely hard to detect, though their very existence was termed a watershed moment when it was confirmed a few years ago.

How LIGO and Virgo detected this cataclysmic collision

Scientists have become proficient in detecting these tiny gravitational waves with the help of observatories in the US and Italy. The observatories, known as LIGO and Virgo, are specifically designed to detect these infinite waves from cataclysmic mergers by measuring how the ripples affect suspended mirrors on Earth. Ever since the first detection of gravitational waves was made by LIGO in 2015, the observatories have detected roughly 67 mergers of black holes and neutron stars.

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Occurring over 5.3 billion parsecs away, the collision is the farthest merger ever detected by LIGO and Virgo, with the waves taking 7 billion years to reach the Earth. This event called GW190521 was so faint that it could have easily been missed. LIGO and Virgo detected only four tiny waves from the merger, which lasted just one-tenth of a second. Scientists used four different algorithms to find the wiggles, eventually leading them to the masses of the merger and to understanding how much energy was released. Astronomers guess that mergers like this are extremely rare which explains why it took a while for the observatories to pick this kind of black hole up.

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(Photo credits: Getty Images)