Deaths of stars

• White dwarfs are the remaining cores of dead stars.
• • Higher-mass white dwarfs are smaller.
• Because nothing can move faster than light, a white dwarf cannot be more massive than 1.4 MSun , the white dwarf limit (or Chandrasekhar limit).
• Electrons must move faster as they are squeezed into a very small space.
• Two types of supernova:

  1. White dwarf supernova
  2. Massive star supernova
• Core degeneracy pressure goes away because electrons combine with protons, making neutrons and neutrinos.
• Neutrons collapse to the centre, forming a neutron star.
• A pulsar is a neutron star that beams radiation along a magnetic axis that is not aligned with the rotation axis.
• Electron degeneracy pressure supports white dwarfs against the crush of gravity.
• White dwarfs don't have hydrogen absorption lines.
• Energy released by the collapse of the core driver the star's outer layers into space.