BRAINCAKEQuasars
Quasars (quasi-stellar objects) were discovered in the 1960s as very bright radio sources. When astronomers looked for them with optical telescopes they found faint, star-like points of light, but with very unusual spectra.
Their spectra show very large optical red shifts. By Hubble's law this means they are extremely far away, making quasars among the most distant objects we can measure. The most distant are billions of light years away, so we see them as they were when the universe was young.
Because they are so far away yet still visible, their power output must be enormous: a single quasar can emit more power than an entire galaxy of hundreds of billions of stars.
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Key terms in this lesson
- red shift
- An increase in the wavelength, and decrease in frequency, of radiation received from a source such as a galaxy that is moving away from the observer.
More in Astrophysics
- Evolution of a Star
- Supernovae, Neutron Stars and Black Holes
- The Schwarzschild Radius
- Type Ia Supernovae as Standard Candles
- The Doppler Effect and Red Shift
- Hubble's Law
- The Big Bang Theory and the Age of the Universe
- Detecting Exoplanets
All 24 lessons in Astrophysics · All AQA A-level Physics topics