B Cassiopeiae was in fact the supernova known as Tycho's Supernova. Subsequent enrichment of galactic halos occurred due to stellar nucleosynthesis and supernova nucleosynthesis. The nebula was the first astronomical object identified corresponding to a historical supernova explosion. The widely observed supernova SN 1054 produced the Crab Nebula. Cosmic rays are generated by stars and certain celestial events such as supernova explosions. Astronomers speculate that this phenomenon is caused by the shock wave from a supernova. This star is the Crab supernova exploding. Natural sources include the sun, lightning and supernova explosions. Explosions can also occur outside of Earth in the universe in events such as supernova. This is helpful for astrophysicists interested in predicting the behavior of supernova remnants. The planet was threatened by their sun turning into a supernova. The only modern nearby supernova, 1987A, has not revealed "r"-process enrichments. Galileo observed and discussed Kepler's supernova in 1604. The Sun does not have enough mass to explode as a supernova. Ia supernova, and its remnant has been detected.