This site is an astronomy tutorial posted by Gene Smith, a professor at UC San Diego. The site contains information on quasars and active galaxies. Information is included on gravitational lensing, black holes, and...

Authored by Nick Strobel, "Astronomy Notes" is an educational resource for introductory astronomy classes for undergraduates. This section discusses the properties of stars. such as apparent magnitude, absolute...

Welcome to the NASA/IPAC Extragalactic Database (NED). It is built around a master list of extragalactic objects for which cross-identifications of names have been established, accurate positions and redshifts entered to...