11. After the supernova explosion , the ejected material expands and becomes a supernova remnant. 12. Designated SN 1998bu, this was a Type Ia supernova explosion . 13. Within the Milky Way galaxy, supernova explosions occur on average once every 40 years. 14. Another potential problem for a Weakless Universe is that supernova explosions are necessarily neutrinoless. 15. Supernova explosions abound; galaxies collide; black holes swallow entire stars.16. These stars undergo carbon fusion, with their lives ending in a core-collapse supernova explosion . 17. NGC 1187 has hosted two supernova explosions since the 1980s. 18. In 1987 Kamiokande also detected neutrinos from a supernova explosion outside the Milky Way. 19. They are thought to be born in the collapse of normal stars in supernova explosions . 20. Furthermore, the expanding shock waves from supernova explosions can trigger the formation of new stars.
