Death of a Star: White Dwarfs and Supernovae: Practice Problem Solutions

1. The core shrinks and heats while hydrogen burns in a shell around it; the outer layers swell and cool, making a red giant.

2. A glowing shell of gas shed by a dying Sun-like star. It has nothing to do with planets; the name comes from how they looked in early telescopes.

3. The hot, dense, Earth-sized core left behind by a Sun-like star. The Chandrasekhar limit, about 1.4 Suns, is the largest mass a white dwarf can have.

4. Fusing iron takes in energy instead of releasing it, so there is no outward pressure to hold up the core.

5. The iron core collapses in under a second to a ball about 20 km across; the outer layers rebound and the star explodes.

6. The supernova of AD 1054, recorded as a 'guest star' by Chinese astronomers.

7. A white dwarf in a binary pulls in gas until it reaches about 1.4 Suns and explodes. These all have nearly the same brightness, so they can be used to measure distances.