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The Question

(Submitted September 05, 1996)

Is Earth affected in any way by quasars? And what exactly are quasars?

The Answer

The word 'quasar' is a contraction of 'quasi-stellar radio source'. The first quasars were discovered in the early 1960s, when astronomers measured their very strong radio emissions. Scientists were subsequently surprised to see faint blue star-like points of light, rather than galaxies, when they looked at the same parts of space with optical telescopes. When the quasar's light was analyzed, it was seen that patterns known from laboratory studies of atomic processes were present with very large redshifts (which means the objects are moving away from us at high velocity!).

We now know that, in fact, most quasars are 'radio quiet', i.e., they have very little radio wave emission, but the name quasar has been kept anyway. We also now know that many (perhaps all) quasars are small regions of intense activity within otherwise normal galaxies.

What is responsible for all the energy that quasars are seen to be producing - sometimes hundreds of times the energy from normal galaxies? The best explanation seems to be that quasars are super-massive black holes in the centers of galaxies. As material spirals into the black holes, a large part of the mass is converted to energy. It is this energy that we see.

Because of their great distances from us, quasars have no real effect on the Earth.

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