During this short interval a supernova can radiate as much energy as the Sun is expected to emit over it's entire life span. The explosion expels much or all of a star’s material. Supernovae can be triggered in one of two ways: The sudden reignition of nuclear fusion in a degenerate star; or by the collapse of the core of a massive star.
Back on July 4 of 1054, a supernova was seen by Chinese, Arab, and possibly Amerindian observers near the star Zeta Tauri. For several months it remained bright enough to be seen during the day! The remnant of SN 1054, which consists of debris ejected during the explosion, is known as the Crab Nebula.