Supernova

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A supernova (pl.: supernovae) is a powerful and luminous explosion of a star. A supernova occurs during the last evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion. The original object, called the progenitor, either collapses to a neutron star or black hole, or is completely destroyed to form a diffuse nebula. The peak optical luminosity of a supernova can be comparable to that of an entire galaxy before fading over several weeks or months. It is expected that supernovae in our galaxy occur on average once every 61 years, although the last to be observed was Kepler's Supernova in 1604. SN 1987A occurred in the Large Magellanic Cloud, a satellite galaxy of our galaxy, in 1987. Several thousand supernovae are typically seen in distant galaxies every year. Theoretical studies indicate that most supernovae are triggered by one of two basic mechanisms: the sudden re-ignition of nuclear fusion in a white dwarf, or the sudden gravitational collapse...

Read on Wikipedia · Image NASA/ESA, The Hubble Key Project Team and The High-Z Supernova Search Team, Public domain