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Novas and supernovas are stars that explode releasing part of their material into space. For a variable time, its brightness increases dramatically. It seems that a new star is born.
A nova is a star which greatly increases its brightness suddenly and then slowly pales, but may continue to exist for some time. A supernova, but the explosion destroys or alters the star. Supernovae are much rarer than novae, observed quite frequently in the photos.
Novae and supernovae provide materials to the universe that will be used to form new stars.
Novas, new stars?
Formerly, a star that appeared to hit where there was nothing, it was called nova, or 'new Star'. But this name is not correct, since these stars existed much before they could see at a glance.
Perhaps appear 10 or 12 novae per year in the milky way, but some are too far away to see or interstellar matter obscures them.To novae occurs them more easily in other nearby galaxies which in ours. A nova increased in several thousands of times its original brightness in a matter of days or hours. After it enters a period of transition, during which pales, and cobra shine again; starting from there pales gradually until you reach your original brightness level.
Novae are stars in a late period of evolution. They explode because their outer layers have formed an excess of helium through nuclear reactions and expands with too much speed to be contained. The star says goodbye to explosively a small fraction of its mass as a layer of gas, increases its brightness, and then normalizes.
The star that remains is a white dwarf, the smallest Member of a binary system subject to a continuous decrease of matter in favour of the larger star. This phenomenon happens with dwarf novae, which arise time and again at regular intervals.
SupernovaeA supernova explosion is more spectacular and destructive of a nova, and much rarer. This is very rare in our Galaxy, and despite his incredible increase in brightness, few can be seen with the naked eye.
Up to 1987 only had identified three throughout history. The best known is which emerged in 1054 and whose remains are known as the Crab Nebula.
Supernovae, as well as the novas, are seen more frequently in other galaxies. Thus, the most recent supernova, which appeared in the southern hemisphere on February 24, 1987, emerged in a satellite Galaxy, the large cloud of Magellan. This supernova, which has unusual features, is the subject of an intense astronomical study.
The very large stars explode into the latter stages of their rapid evolution, as a result of gravitational collapse. When the pressure created by the nuclear processes, already cannot withstand the weight of the outer layers and the star explodes. It is called type II supernova.
A type I supernova arises similar to a nova. He is a member of a binary system which receives the flow of fuel by capturing material, fellow.
Of a supernova explosion are few remains, except for the layer of gas that expands. A famous example is the Crab Nebula; in its center there is a pulsar, or star of neutrons that rotates at high speed.
Translation for educational purposes authorized by: Astronomía: Tierra, Sistema Solar y Universo