Active Galactic Nuclei:
Small fraction of galaxies have extremely
bright unresolved star-like nuclei
Very large energy generation
Brightness often varies quickly
Implies small size (changes not smeared out by light-travel time)
High velocities often seen (> 10,000 km/s in lines)
Emission all over the electro-magnetic spectrum
Jets seen emerging from galaxies
Think about the implications of jets.
What do they imply?