Adopey.128
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Wed Mar 3 19:56:10 1982
superluminal quasars
Here's the basis for my question about quasars moving faster than light,
from the August 22, 1981 issue of Science News:
Just a few months ago, only four quasars with components moving
apart at apparent velocities faster than the speed of light had
been identified. Now... there are six.
... Each of the six has at least one pair of components
separating at velocities that, from our vantage point, appear to
be faster than light. The apparent expansion velocities are all
in the range of 3 to 10 times the speed of light, with the exact
numbers depending on which assumed value of the Hubble
constant... is used.
... When astronomers refer to "superluminal expansion", they
don't necessarily mean the components involved actually are
separating from each other at faster than the speed of light.
Built into the phrase... is the idea ... "as it appears from
earth." The leading explanation... calls on a geometric
situation in which a relativistic jet from the quasar is moving
out from the core at a small angle to our line of sight to the
core. During any given period since light left the jet on its
route towards us, the jet itself has moved almost the same
distance toward us as well. The light from its second position
therefore reaches us only a short time after the light from its
first position.
... Most astronomers assume this to be what is responsible for
the measurements of superluminal expansions, although there is
plenty of uneasiness over the requirement of having the fairly
special line-of-sight orientation.... Six of twelve, or half,
the appropriately analyzed quasars have shown it, a troublingly
high frequency. However, the twelve are not random samples,
but highly selective samples, and that might help explain away
the difficulty.
Now -- does anyone have any later information on this? (I note in
passing that we seem to have yet another situation where special
alignments are involved, as in the red shift/blue shift discussion.)
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