Quasars look like any normal star through an optical telescope. It wasn t until the 1950 s, when radio astronomy was first developed, that astronomers realized these extragalactic objects are emitting massive amounts of radio energy. This important discovery was named a quasar, short for Quasi-stellar radio source . By waiting for known radio sources to pass behind the moon, optical and radio data could be combined to give astronomers the precise location of quasars in the sky.
Quasars are among the most distant, energetic objects ever observed.
Even though individual quasars are brighter than hundreds of galaxies put together, many are smaller than the size of our own solar system. Radio astronomers use a system of numbers to name objects in the sky. 3C273 was named in the 3rd Cambridge catalog as the 273rd radio source identified. 3C273, along with 3C48, were the first quasars to be identified. These objects had bizarre spectra unlike any ever studied before.