Astronomical Spectroscopy - Quasars

Quasars

In the 1950s, some strong radio sources were found to be associated with very dim objects that seemed to be very red. These were named Quasi-stellar radio sources, or quasars. When the first spectrum of one of these objects was taken, it was something of a mystery, with absorption lines at wavelengths where none were expected. It was soon realised that what was being seen was a normal galactic spectrum, but highly redshifted. According to Hubble's Law, this implied that the quasar must be extremely distant, and therefore highly luminous. Quasars are now thought to be galaxies forming, with their extreme energy output being powered by super-massive black holes.

Read more about this topic:  Astronomical Spectroscopy