Science & Technology

The Black Hole – A Dark Phenomenon

By Elyas Layachi

Volume 2 Issue 2

November 19, 2021

The Black Hole – A Dark Phenomenon

Image provided by Katie Bouman

Introduction

Ever since the telescope was invented in 1608 by Hans Lippershey, scientists have been making discoveries regarding the universe around us and our place in it. From determining the Earth's and planets' orbits around the sun to discovering that the universe is ever-expanding, we now know more about our universe than ever before in human history. However, most phenomena we have discovered are still theories, such as black holes. While scientists have laws, observations, and general ideas about what black holes are, they have not been limited in their ability to directly study them.


History of Black Holes

Black holes were originally theorized by astronomer and astrophysicist Karl Schwarzchild. However, Einstein's theory of relativity helped prove Schwarzschild's black hole theory. Using E = mc^2, Einstein theorized that gravity could behave like matter. This became known as Einstein’s Theory of Relativity, and it introduced space time, which adds a fourth dimension to the current dimensions of length, width, and depth: time. We cannot see space time directly, but black holes prove space time exists by “bending” the space time fabric. Schwarzschild, using Einstein’s Theory of Relativity, theorized that there comes a point where every particle, including light, becomes gravitationally trapped. He dubbed this point the “event horizon,” and he also theorized that as matter approaches the event horizon, time slows to a complete standstill. Several decades later, astronomers found evidence to support this theory, and named the systems they discovered black holes, since even light cannot escape them. Astronomers discovered Cygnus X-1, the first black hole discovered, by observing it suck gas and matter away from a blue supergiant star. This proved black holes have an immense gravitational force, and since scientists could not physically see the black hole, due to it trapping light past the event horizon, this proved Schwarzschild’s theory.


Current Scientific Understanding

Today, the current acceptable definition of a black hole is that it is a region of space time where gravity is so strong that nothing – no particles, or even electromagnetic radiation such as light – can escape it. According to NASA, black holes form when the center of a very massive star has so much gravitational force that it collapses upon itself. This causes a supernova, or an exploding star, that blasts parts of the star into space. Out of the supernova comes a black hole, which increases in size as it consumes more matter.

Black holes have three parts, or layers: the outer and inner event horizon, and the point of singularity. The event horizon, both inner and outer portions, is the boundary around the mouth of the black hole, and once light passes this part, it can no longer escape the gravitational force of the black hole. The point of singularity, which is the inner region of the black hole, is the most massive part of the black hole. This region is the point in space time where the mass of the black hole is concentrated. Scientists theorize that the point of singularity has an infinite density and therefore is a point of infinite curvature of space time.

At the center of our Milky Way galaxy exists a black hole named Sagittarius A, and all stars and star systems in our galaxy, including our solar system, orbit around the supermassive black hole. Astronomers Bruce Balick and Rober Brown used the U.S. National Radio Astronomy Observatory’s radio telescope to study the center of the Milky Way. They found that a small point, or central core, was emitting immensely powerful radio waves. With more observations, the astronomers concluded a supermassive black hole was at the center of the Milky Way.

The Future of Black Hole Research

Today, scientists use several satellites and tools to help them observe black holes, including the Hubble Space Telescope, the ASTRO-H Satellite, the Swift mission, and radio telescopes on Earth. In the future, scientists at NASA plan to develop more satellites and telescopes to study the relationship between gamma ray emissions and black hole gravity.

I hope you learned something new about black holes!