Quasars have large red shifts, indicative of great distance from the earth, but have variability with periods of weeks or months which indicate that they are small. Their size is on the order of light weeks, but are brighter than our galaxy which is about 100,000 light years across. The red shift is usually stated in terms of a parameter z which is defined by
The name "qausar" is derived from an early description "QUAsi-StellAR-Objects" .This description was used since they appeared to be faint stars, but they had the dramatically large red shifts which indicated that they were something else.
More on Quasars
The observed quasar red shifts correspond to a speed range of .15 c to 0.91 c. Using a Hubble constant of 55 km/s per megaparsec gives distances of 2.6 to 16 billion light years for these quasars.
The evidence on quasars suggests greater luminosity than our entire galaxy of 200 billion stars. The turbulent velocities in the quasars are up to a few 10s of thousands of m/s, so are constantly occurring explosions, i.e., that kind of turbulent velocity in a chemical reaction would make a potent bomb. Some of the quasars are a few light-days across, as evidenced by their periods of variability, and yet much brighter than our entire galaxy which is 100,000 light years across. This makes them about solar system size. The suggested energy source is a black hole with several billion solar masses.
There are examples of multiple images of quasars caused by gravitational lens effects.
Since light is bent by a gravity field according to general relativity, there is a possibility of focusing effects like that of a lens when there is a large collection of mass near the path of the light to us. The two brighter objects in the sketch to the right are interpreted as two images of the same quasar, Q0957 +561. The focusing matter is an intervening giant galaxy.