An artist concept of a galaxy with a supermassive black hole at its core. Image credit: NASA/JPL-Caltech
The first person to effectively answer the question what are black holes was Karl Schwarzchild by using the work of Albert Einstein. He broached the subject with his use of Einstein’s theory of general relativity. According to him a black hole is a place where the gravity well is so great that a gravitational time dilation has occurred. This causes time to stop. It also causes an event horizon to form into which objects can fall or be pulled, but never reappear. Although invisible, they are called black because they do not reflect anything that hits them. They absorb all light. Analysis has shown that a black hole does possess a temperature and Hawking radiation. A black hole can only be seen by its interaction with the matter around it.
There are many interesting black hole facts to be had. Here are a few of the best.
There is no limit to how small or how large a black hole can be. The size and mass of a black hole are directly related. The more massive a black hole is, the more space it takes up. In fact, the Schwarzschild radius ( the radius of the event horizon of a black hole) and the mass are directly proportional to one another. So, if one black hole has ten times the mass as much as another, its radius will be ten times the others.
The nearest black hole is about 16 quadrillion kilometers for Earth(1,600 light years).
There is a super massive black hole at the center of the Milky Way galaxy. It is about 4 million solar masses. Luckily, it is over 30,000 light years away.
Some scientists think that black holes eventually destroy themselves. The theory is that the black hole expels energy that it gains from its mass. As the energy is expelled the mass is consumed until the black hole is gone. This is a quick explanation for something that takes hundreds of millions of years to accomplish.
Explaining ‘what are black holes’ is easy. Understanding what they are and how they interact in space is much more complex.
We have written many articles about black holes for Universe Today. Here are some facts about black holes, and here’s an article about maximizing survival time inside the event horizon of a black hole.
If you’d like more info on black holes, check out NASA Science Page about Black Holes, and here’s more information from NASA from their educational pages.
We’ve also recorded an episode of Astronomy Cast all about black holes. Listen here, Episode 18: Black Holes Big and Small.
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