From the archive of About Facts in 2014. What is a black hole and where can I buy one? To answer the last question first, when I find out I'll let you know, but I bet it will be the Department of Defense. People have predicted tiny versions of black holes will someday be used as weapons. Boy, I hope not, because after you read this article and find out exactly how powerful a black hole is you will understand my fear. It is believed that black holes come from collapsed stars. The theory is eventually a star will use up the fuel that keeps it burning. The gravitational forces that were kept at bay by the active star now force it to collapse upon itself. As it does this, heat is created and the star get so hot it explodes. The exploding star is a supernova and some of its mass is blown away, but what is left is compressed further and so massive the gravitational field stops anything from escaping, including light. Since you cannot see any light coming from it, it looks like a black spot in space. Black holes seem to come in different sizes. There are stellar black holes, these are the ones that come from collapsed stars and there are also black holes containing the mass of billions of stars and there are the tiny black holes. Galaxies that emit far more energy than normal are known as active galaxies. There are several types of active galaxies: Seyferts, quasars, and blazars. Most scientists believe that, even though these types look very different to us, they are really all the same thing viewed from different directions! Quasars are active galaxies which are all very, very, far away from us. Some of the quasars we have seen so far are 15 billion light-years away! Blazars are very bright in the radio band, which results from looking directly down a jet which is emitting in synchrotron radiation. On the other hand, if the jet is not pointing toward you at all, and the dusty disk of material which lies in the plane of the galaxy is in the way, you would see just what we see from the Seyferts. By measuring their redshifts, we find that Seyferts are much closer to us than quasars or blazars. It is believed that these objects are the home of massive black holes. They could be billions of times the size of a stellar black hole as I stated before. Let’s examine the different types of objects containing these super massive holes and see what their differences are. Seyferts are named after Carl Seyfert an astronomer that took photographs of them in the 1940s. They are spiral galaxies with a bizarre object in the center. The center varies in brightness over a period of months. They are less than 1 parsec in size. A parsec is defined as the distance from the Sun which would result in a parallax of 1 second of arc as seen from Earth, in later years radio telescopes examined Seyferts and found structures on opposite sides of the galaxies and a tiny source of radio emission at the nucleus. There are electrons being shot out in narrow beams. In summary this galaxy has jets, lobes and a very hot spot where the jets hit the interstellar medium. Quasars are Seyfert Galaxies and Radio Galaxies, where the nucleus out shines all the stars by an outstanding factor of 10 to 1000 times. Quasars seem to be further away than ordinary Seyfert galaxies. If this is true than maybe they are not all the same. Blazars are believed to be a subclass of Active Galactic Nuclei, but their jets are pointed toward Earth. They emit the widest range of frequencies. An object cannot be classified as a Blazar unless it has one of the following properties: Tiny black holes may be formed by mass being compressed into a very small package. Suppose our sun was compressed into the size of a ball, you would now have a tiny black hole. I have always thought maybe relatively small pieces of matter that were shot out from a star were pulled together by gravity and formed the tiny black hole, but I'm no scientist. So how do we know black holes exist if we can't see them? Sometimes we are lucky enough to see the matter flowing into them. We can also detect X-ray emissions caused by the superheating of matter falling into the black hole. If a binary system is found with a black hole, it makes it easier to detect because of matter being drawn off the companion star. Added to the article: I think black holes may still have surprises left for us. Some have suspicions there could be galaxies inside black holes. We think they crush anything entering them, but could there be a way to get inside one which we will discover one day, and if we do what might we see? If physics is different inside them maybe many things, we believe about what they contain could be wrong. We thought nothing could live at the tremendous pressures at the deepest parts of the ocean, but we were entirely wrong. Could there be thriving civilization in at least some of them and maybe they are trapped inside, or maybe they have discovered technology which allows them to travel out and back. As we move on and explore space, will we ever explore inside a black hole. While most scientists say never and it is impossible, you never know what the mind of man might come up with. Who ever thought we could have created the Parker Probe which flies through the atmosphere of the sun?
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