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Q&A: Galaxies, Galaxy Clusters, AGN, and Quasars
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Q:
I'm confused about something. A red shift of 0.461 means 3C295
is slightly less than five billion light years from us. Yet the
article goes on to say that the radio lobes we see were probably
blasted out by a supermassive black hole in the nucleus less
than a million years ago. If this is the case, how can we see
them at all. If 3C295 really is five billion light years away,
doesn't this mean we could see the results of an explosion in
any form, optical, radio, or X-ray, that occurred less than a
million years ago? I'm missing something here, but it is
confusing.
A:
The age of a million years for the jets refers to the age of the
outburst in the source. Since the light took 5 billion years to
get here, we are seeing the outburst more than 5 billion years
after it occurred. It's similar to finding a photograph in a 100
year-old time capsule of a 5 year old child.
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