What's in a Name?

After the discovery of the initial radio quasars, it was found that many similar objects did not emit radio waves. These were termed Quasistellar Objects or QSOs. Now, all of these are often termed quasars, whether they emit radio waves or not.

More than 90 percent of the quasars discovered to date have no detectable radio emission. One makes a distinction between radio loud quasars and radio quiet quasars, based on whether we detect significant radio emission from them. Later we will see that strong radio emission from quasars and galaxies almost always involves elliptical galaxies, never spirals.