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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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