AST-1002 Lecture Notes - Lecture 12: Planetary Nebula, Disc Galaxy, White Dwarf
Document Summary
Explanation: far away, long ago, a star exploded. Supernova 1994d, visible as the bright spot on the lower left, occurred in the outskirts of disk galaxy ngc 4526. Supernova 1994d was not of interest for how different it was, but rather for how similar it was to other supernovae. In fact, the light emitted during the weeks after its explosion caused it to be given the familiar designation of a type ia supernova. If all type ia supernovae have the same intrinsic brightness, then the dimmer a supernova appears, the farther away it must be. By calibrating a precise brightness-distance relation, astronomers are able to estimate not only the expansion rate of the universe but also the geometry of the universe we live in. The death of a g-star, such as our sun: In about 5 billion years the sun is going to run out of hydrogen in its central core.
