Black holes and Dark Matter

The title attracted you right? Whom won't it? Right from high school science enthusiasts to research doctorate physicists, the term 'black hole' and 'dark matter' intrigues them!

This blog attempts unpack the concepts of Black holes and Dark matter and also tries discover a relation between them.

First things first:

What is a Black hole?

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.

Because no light can get out, people can't see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.

Could a Black Hole Destroy Earth?Black holes do not go around in space eating stars, moons and planets. Earth will not fall into a black hole because no black hole is close enough to the solar system for Earth to do that.

Even if a black hole the same mass as the sun were to take the place of the sun, Earth still would not fall in. The black hole would have the same gravity as the sun. Earth and the other planets would orbit the black hole as they orbit the sun now.

The sun will never turn into a black hole. The sun is not a big enough star to make a black hole.

What Is Dark Matter?

Roughly 80 percent of the mass of the universe is made up of material that scientists cannot directly observe. Known as dark matter, this bizarre ingredient does not emit light or energy.

Studies of other galaxies in the 1950s first indicated that the universe contained more matter than seen by the naked eye. Support for dark matter has grown, and although no solid direct evidence of dark matter has been detected, there have been strong possibilities in recent years.

By fitting a theoretical model of the composition of the universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter.

We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter.

Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.

The above answers from NASA gives us a fair picture of black holes and dark matter.

With this acceptable lucidity, let us proceed further to explore the relation between these two.

The most popular and fascinating view is that dark matter is made of black holes formed during the first second of our universe's existence, known as primordial black holes .

“There seems to be a mysterious link between the amount of dark matter a galaxy holds and the size of its central black hole, even though the two operate on vastly different scales,” says lead author Akos Bogdan of the Harvard-Smithsonian Center for Astrophysics (CfA).

Dark matter, the mysterious extra mass in the universe that emits no light yet exerts a gravitational pull, may actually be made up of primordial black holes that originated with The Big Bang.

However, not everyone is convinced, with some physicists saying that these primordial black holes are unlikely to explain all the dark matter found in the universe.

The idea that black holes existing today could make up all of the dark matter in the universe is relatively controversial. In February 2016, the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced it had detected two merging black holes that were 29 and 36 times as massive as our sun. Primordial black holes in that mass range have not been ruled out, making some researchers hopeful.

But some physicists doubt these celestial objects could explain much of the dark matter in the universe.

This blog just gave a whirl on the basic abstracts of black holes, dark matter and the relationship between them. The exploration doesn't stop. There's more to it than we know.

Below are few enthralling links to quench our thirst for the quest:

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