Welcome to the Astro Minute, where we’re exploring the universe sixty seconds at a time. I’m Lauren Smyth, and today we’re looking at supernovae.



High-mass stars age into red supergiants, fusing helium in their core and hydrogen in the surrounding shell. But their extra mass ignites more stages of nuclear fusion, ending with an iron core surrounded by multiple shells of fusing material. Core fusion stops with iron, and under the weight of the shells, the earth-sized core suddenly collapses to only a few miles across, smashing its atoms together so tightly that protons and electrons combine to form neutrons. The neutron core stops the collapse abruptly, and a massive shock wave violently ejects the outer shells, creating a supernova a hundred billion times more luminous than our sun.



Thousands of extragalactic supernovae are seen each year, but occur only once or twice per century in our galaxy.



I’m Lauren Smyth, and that’s your AstroMinute.