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A team of researchers from the California Institute of Technology has discovered a supermassive black hole binary system located 9 billion light-years from Earth. Usually, there is a single supermassive black hole at the center of a galaxy with a mass of millions to billions of the mass of the Sun.
Exceptionally, two giant black holes can temporarily coexist in one galaxy only when two galaxies collide to form one giant galaxy.
The reason it is said to be temporary is because two black holes with strong gravitational force pull each other and merge into one. However, since this process occurs in a very short time on an astronomical basis, it was difficult to observe in practice.
A team of researchers led by Sandra O’Neill of the California Institute of Technology made an unusual discovery while observing the Blazer PKS 2131-021. A blazer is a particularly bright object among quasars, the brightest objects in the universe, and its identity is thought to be a jet emitted by a supermassive black hole.
A supermassive black hole pulls in too much matter with gravity, and then it doesn’t absorb all of it and then ejects it. For reference, PKS 2131-021 emits particles at 99.98% of the speed of light at a location 9 billion light-years away from Earth.
An unusual fact discovered by the research team is that the brightness of PKS 2131-021 changes periodically. What makes this surprising is that the blazer is actually a supermassive black hole with a mass hundreds of millions of times the mass of the Sun. Only other supermassive black holes can periodically shake such a massive black hole.
The research team analyzed 45 years of astronomical observation data collected from five telescopes in Earth and space, and confirmed that the brightness change of PKS 2131-021 occurs every two years. And conversely, using this, the mass and orbit of the companion black hole, which are difficult to observe directly from the Earth, were estimated.
As a result, it is estimated that the PKS 2131-021 black hole binary system orbits each other at a distance of 2000 times the Earth-Sun distance and 50 times the Sun-Pluto distance. It seems quite a distance, but it is too close for the distance between two black holes with hundreds of millions of solar masses. The research team predicted that PKS 2131-021 would coalesce within the next 10,000 years.
It is a distant future by human standards, but considering the age of large galaxies similar to the age of the universe, it is a very short time.
According to Einstein’s theory of relativity, a powerful gravitational wave is generated and spread throughout the universe in the process of merging these huge celestial bodies into one.
However, since PKS 2131-021 is rather large, it is difficult to accurately measure it with existing observation equipment. The research team expects to be able to observe the details of the supermassive black hole binary system using next-generation observation equipment.
Columnist Lee Kwang-sik [email protected]