What is a supernova, and what can it tell us about the universe?
A supernova is the explosive death of a star, which unleashes a burst of light through the cosmos. Supernovas happen in two different ways: • When massive stars run out of fresh nuclear fuel, there is no more pressure to sustain them against their own weight. The central part of such a star then collapses. The outer layers of the star fall in on the core and then rebound in a tremendous explosion. • Matter piling up on the compressed core of an already-dead star, known as a white dwarf, can reach sufficient density to trigger a thermonuclear explosion. These violent deaths occur about once a century in a typical spiral galaxy like our Milky Way. Every 200-300 years we discover a supernova that happens to be bright and close enough to be visible to the unaided eye. The last supernova seen in our galaxy was discovered in 1604. When visible to the eye they appear in the sky as a “new” (Latin: “nova”) star. A supernova observed in the “nearby” Large Magellanic Cloud (an irregular galaxy ou
