Relating Follicly-Challenged Compact Stars to Bald Black Holes

Understand

Compact stars satisfy certain no-hair relations through which their multipole moments are given by their mass, spin and quadrupole moment.

• These relations are approximately independent of their equation of state, relating pressure to density.
• Such relations are similar to the black hole no-hair theorems, but these possess event horizons inside which information that led to their formation can hide.
• Compact stars do not possess horizons, so whether their no-hair relations are related to the black hole ones is unclear.