White Dwarf

1
White Dwarf
2
Collapse

• The core of a giant star collapses as helium
  fuses.
• Outer layers continue to expand
• Loses over half its mass
• The lost mass comes off in helium flash
  explosions.

core
outer layers of gas
3
Planetary Nebulae

• Ejected gas from a star is lit up by the
  shrinking core.
• Round shape
• Glows with colors seen from planets
• The gas is called a planetary nebula.
• Not really part of a planet

4
Degenerate Matter

• After explosions the remaining core collapses due
  to gravity.
• Radiation too weak
• At high density, the electromagnetic force
  between electrons holds the material of the core
  apart.
• This compressed material is degenerate matter.
• Core of giant stars
• Sun mass in Earth size

5
Fate of the Sun

• The Sun will collapse after millions of years as
  a giant.
• Heat to class A or B
• Shrink to Earth size
• The end of the sun will be a small, hot star that
  will last until the remaining material burns up.

Sun
6
Bipolar Nebulae

• Planetary nebulae can have multiple flashes.
• Ring of ejected matter around the core
• Later flashes blocked by ring
• The gas goes in the remaining two directions
  forming a dumbbell or hourglass shape.

7
Bare Core

• Stars less than 8 M? will all end by helium
  flashes as gas is ejected.
• The remaining core is called a white dwarf.
• The white dwarf will cool over billions of years
  until it is black.