Theoretically, when we look out there through a telescope, we are looking back through time. Is it possible (though not likely) that what we see through that lens is all entirely in the past and that the stars could now have disappeared?
No. Most stars have lifespans of thousands of millions of years. For relatively close galaxies such as Centaurus A or the Virgo cluster the light-travel time is much less than the stellar lifetime, so most of the stars that form these galaxies are still in existence. Even the stars that have died are mostly still there, as white dwarfs, neutron stars or black holes, even though they are too faint to be seen by optical telescopes.
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