Astronomers have detected what they believe to be the most powerful, most massive, most distant merger of two black holes in the history of the universe, releasing the energy of eight suns. This is an important observation because it has led to the formation of a new type of black hole – an intermediate black hole, the first one to be discovered so far.
Types of Black Holes
Theoretically speaking, there are four types of black holes:
Micro Black Holes: Also known as quantum mechanical black holes, the micro black holes are hypothetical. These micro black holes have a certain mass limit. According to the concept of Schwarzchild radius and Compton wavelength, the minimum mass of a micro black hole is 22 micro-grams, also known as the Planck mass.
Stellar Mass Black Holes: The second in the classification of black holes is a stellar-mass black hole. These are one of the most studied black holes and unlike the micro ones, they do exist in nature. Their formation mechanism is also known to scientists. As the name suggests, a stellar-mass black hole forms when a massive star collapses.
Supermassive Black Holes: the supermassive black holes are the largest black holes that are found at the centers of the galaxies. They can be a billion times as massive as the Sun.
Intermediate Black Holes: They lie in between the stellar and supermassive black holes. Neither too small nor too big.
The Merger of Black Holes
According to astronomers, two black holes with masses about 85 and 66 times the mass of the sun, collided to produce a signal, in the most massive merger ever detected. The signal, called GW190521, appears to represent the exact moment the two black holes crashed into each other.
Researchers say the event created an even more massive black hole, about 142 times the mass of the sun. It also released a huge “bang” of leftover energy, equivalent to about eight solar masses, in the form of gravitational waves able to be detected on Earth.
How Did They Detect The Merger?
Black holes have enormous gravity. They are so powerful that even light cannot escape them. So how did we get the information? The answer is gravitational waves. Predicted by Einstein’s general theory of relativity, gravitational waves are the ripples in space-time. They are produced because of accelerating bodies. When two black holes merge with each other, they release some energy in the form of these gravitational waves.
More on black holes:
- What happens when a star gets too close to a black hole?
- The famous black hole information paradox
- A brief history of black holes from 1784 to 2020
On May 21, 2019, using the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO) interferometers in the U.S. and the Virgo detector in Italy, a team of scientists detected GW190521. They published their findings in two papers: Physical Review Letters and The Astrophysical Letters Journal.
Gravitational waves are a rich source of information. They tell a lot about the merging black holes.
The Unanswered Questions
The event GW190521 has puzzled astrophysicists. They believe that the black holes that merged into each other are unique in their sizes. Black holes of 85 and 66 solar masses cannot form because of a collapsing star. Scientists believe that these two black holes are themselves a result of mergers.
Virgo researcher Nelson Christensen, from the French National Centre for Scientific Research (CNRS), said “The fact that we’re seeing a black hole in this mass gap will make a lot of astrophysicists scratch their heads and try to figure out how these black holes were made.”
“This event opens more questions than it provides answers,” said LIGO researcher Alan Weinstein, a physics professor at Caltech. “From the perspective of discovery and physics, it’s a very exciting thing.“