- Recall that quasars are distant galaxies with high redshifts
- Describe the discovery of quasars by astronomers

These stand for quasi-stellar objects. They appear like stars but are actually very different. They are believed to be galaxies that emit large amounts of x-rays, ultra violet light and sometimes radio waves. Qusars are believed to be caused by matter falling into a black hole at the centre of the galaxies, causing jets of matter to shoot out at high speed.

They show large redshifts in their light meaning they are moving away from us at very high speeds and are typically billions of light years away from us. They are the oldest objects that we know about.

Qusars were first identified by their high redshift (how fast they are moving away from us) and emission of radio waves.

1950s scientists detected them by radio telescope but were unable to detect a visible object associated with them until 1960. Their broad emission lines meant they were not stars. In 1962, scientists measured a source as it occulted the Moon, showing a large redshift in the spectral lines. This redshift was given the name "quasi-stellar radio sources.


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See also...

Radiation & Active Galaxies page

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StarChild Quasars

Imagine the Universe Ask an Astrophysicist: Quasars & Active Galaxies

Dr. John Simonetti,Dept of Physics, Virginia Tech Quasars FAQ


  • What are quasars?
  • How did we discover them?
  • What is special about them?