What a supernova?
|Automatic translation||Updated June 01, 2013|
A supernova is visible phenomenon, directly from the cataclysmic explosion of a star that leads to its destruction and thus the death of the star. This explosion is accompanied by massive increases its brightness as seen from Earth, which can last up to several weeks and even months. It is visible in daylight and at night it can be as bright as the moon and even give a shadow to objects. A supernova appears so often as a new star, hence its name, nova. Supernovae are rare events in our Milky Way, about one to three per century, against the scale of the Universe we observe every day. It was during the supernova explosion the star releases the chemical elements, it was synthesized in its existence and during the explosion itself. The shock wave from the supernova favors the formation of new stars, accelerating the contraction of regions of gas and dust in the interstellar medium. The novas, unlike supernovae come from thermonuclear explosions, causing a partial destruction of the star by expelling part of its surface into interstellar space. Our sun will not end his life as a supernova but much quieter.
Its radius shrinks to 10 km The final density is enormous, the nuclei can not resist and the heart of the star becomes a giant nucleus of neutrons. The collapse caused a terrible explosion, which will project the upper layers of the star into space and it will shine in the sky, a supernova. Above 5 times the mass of the Sun, the collapse is extremely violent. It can not be stopped. The heart of the star becomes a black hole.
Image: List of the supernovae
Image: The most famous supernova of the history of the astronomy. SN 1054 is a supernova the explosion of which was seen since the Earth from July 4th, 1054, called misty of the crab today which is situated in our galaxy in the constellation of the bull.
Stellar explosions in NGC 6984
Supernovae are extremely luminous explosions of stars, so bright they are remarkable among the stars shining like a spiral galaxy NGC 6984. In the picture below you can see against near the center right, a very bright star that shows the end of its life in a spectacular explosion. Already in 2012, the star named SN 2012im expelled much of its material in the middle of the spiral galaxy NGC 6984 arm. And in 2013 it was the turn of SN 2013ek another supernova explodes in this galaxy. It is it which is visible in the foreground of this picture, as a very bright star just above and right of the center of the galaxy.
Two independent supernovae same class, which explode a year apart is a very unlikely event. It was initially believed that SN 2013ek was a revival of SN 2012im, but other observations showed that they were well separated, although they may be closely related by an unknown cause.NB: Supernovae of type II, Ib and Ic are stars at the end of life. Type II supernovae have a spectrum that contains hydrogen, while Ib and Ic supernovae type are stars who have already used up their hydrogen, so it does not appear on their spectrum. Type Ic supernovae have also exhausted their helium and does not appear in the spectrum.
Image: The supernova SN 2013ek that can be seen near the center right of the spiral galaxy NGC 6984 is an extremely bright star that announces the end of its life in a spectacular explosion. Image Credit: NASA / ESA / Hubble.