Paul Winalski wrote:
It depends on the particular stars. Some stars with a rather large
proper motion (e.g., Alpha Centauri, Arcturus) might be quite far
away from where they are now. The Ursa Major moving group has large
enough proper motion that the Big Dipper would look very different
100 million years ago than it does now.

Then there are some very young stars that might not even have
existed 100 million years ago. Rigel, for instance. There might
well be no Pleiades in Taurus, and I suspect Orion might look
very different.

A hundred million years ago, the sky would have been totally
unrecognizable. None of the stars you see today would be where they
are now. They could be halfway across the sky, or totally invisible,
or they might not even exist. (That's particularly possible with
the brightest stars.)

Just a million years would probably be enough to make the sky just
about impossible to recognize, without specialized software.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
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