If you have any interest in astronomy, then you have most likely heard of black holes. Or you may have watched the movie Interstellar and had no idea what was going on but knew black holes were at the center of it. They are extremely massive objects that we cannot see, yet they affect their surroundings in measurable ways. It’s intriguing to think that something exists where even light, the fastest moving source in all of the universe, cannot escape the gravitational pull of a black hole. Even time itself is altered in the presence of a black hole.
However, not everything about them is a mystery. We know how some of them form and their properties. When a massive star that has the mass of roughly more than eight times the mass of our sun reaches the end of its life span, it dies in a supernova explosion. What remains of the core becomes either a neutron star or a black hole. A black hole would occur if enough of the star’s mass fell onto it’s core. There is a region around a black hole called the event horizon, where if anything were to enter it, it could never escape. At the center, there is the singularity, which is a point of infinite density.
Similar to other objects in the universe such as stars, black holes can be categorized based on their mass. There are 4 different categories based solely on mass: Stellar Mass Black holes, Intermediate Mass black holes, Supermassive Black Holes, and Primordial Black holes. Stellar Mass black holes form when a massive star dies and can be about 5 to tens of times the mass of the sun. Supermassive black holes have a mass of between one hundred thousand and 10 billion times the mass of the sun. We do not know how these extremely massive objects came into existence, but we definitely know they exist. In April of 2019, the very first image of a black hole was produced by the Event Horizon Telescope, and it contained the image of a supermassive black hole that was at the center of the galaxy “M87”. We also know that one exists at the center of every galaxy, including our own. Intermediate-Mass Black Holes, which have masses of a few hundred to hundreds of thousands of solar masses, are known to exist due to the now detectable gravitational waves that they emit when two black holes collide. Primordial Black Holes are thought to be extremely small black holes that existed right after the Big Bang. Astronomers are currently searching for observational evidence of these black holes.
According to our current knowledge, Black holes can only be described by their mass, rotation, and charge. Any other information describing the black hole would be hidden behind the event horizon. Most black holes are expected to be spinning very rapidly, but they are unlikely to have a significant amount of charge, simply because large amounts of matter usually contain about the same numbers of protons and electrons, so the charge cancels out.
What lies inside Black holes will forever remain a mystery because it is impossible to go inside them and return information, but they are still important to further our understanding of the universe, and they make great characters in science fiction movies.
Western Slope Skies is produced by the Black Canyon Astronomical Society. This episode was written and recorded by Noah Reedy, an astronomy student of Dr. Catherine Whiting at Colorado Mesa University.