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.

1st black holes image
Supermassive black hole

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.

Read all the articles of our Basics of Astrophysics series here

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.

Numerical simulation of a heavy black hole merger by Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut) on YouTube

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.

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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.

LIGO Black Hole Merger
LIGO/Caltech/MIT/R. Hurt (IPAC)

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.

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How about the reason it’s hard to find middle range black holes is because they are constantly growing without the introduction of matter. The center of a black hole of certain size must be frozen in time (time-space warping till causality breaks) but the event horizon moves through space-time, so the event horizon would streach space-time in a 4 dimensional cone shape, making it grow bigger the older it is, and amplify gravity to match.

Fred Edwards
Fred Edwards

What if stuff wasn’t torn apart when it went into a black hole but stored,hence having the Super Massive Black Holes so early in time. If quasars are made by them then that material can’t be torn apart. Just thinking.

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