By: Bailey Zimmerly

Black holes are formed when giant stars explode. At first the giant star is a nebula or a cool cloud of gas and dust. A few hundred thousand years later it becomes a protostar or a glowing ball of gas. After this stage, the star will be a main sequence star for the majority of it’s life. After about 10 million years of the main sequence, the star turns into a red supergiant. This stage will be a little less than half as long as the main sequence star. In this sequence the star expands from 2 million miles across to 60 million miles across.

After the stars are past the red supergiant stage, the outer layer of the star explodes forming a supernova. This is a very short stages that only lasts for 1 or 2 years at the most. After this stage, the star becomes either a really dense neutron star or a black hole. After the supernova, there is a stellar core that remains after the supernova. If the core of the mass is greater than three times the solar masses, the star continues to contract till it becomes a black hole.

Black holes have such strong gravity that not even light can escape it. As a result of this issue, black holes are invisible. There is however an exception to black holes being invisible. If the black hole has a close companion star, it can pull gas from it forming a disk that spirals around the black hole very rapidly. In the center of the black hole there is singularity, the theoretical region of infinite density, pressure, and temperature.

Astronomers are still not sure, but have long suspected that a very massive black hole existed at the center of our galaxy, created early in the history of the universe. Their suspicion focused on a compact radio source, also found to emit x-rays, hidden behind dust clouds in the constellation of Sagittarius. A large star in that region was found to orbit a dark concentration of mass, estimated at 3.7 million times the mass of our Sun. There is no other reason to conclude that this is indeed an enormous black hole.

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