Stars are really, really far away from Earth. Even the nearest star is so far that its distance is hard to write in ordinary units: Alpha Centauri (which we can't see from Rochester) is about 38,000,000,000,000 kilometers away. Yikes!
A more convenient unit for the distance to celestial objects is the LIGHT-YEAR: the distance a light ray would travel during a year. The bright star Vega (nearly overhead right now) is about 27 light years away. That means that the light we are seeing now must have left the star 27 years ago.
Here are distances to some of the stars you can see tonight, if you know where to look. Please ask one of the astronomers for help if you can't find one.
Star Distance (light years)
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Altair 17
Vega 27
Arcturus 36
Dubhe 120
Antares 190
Deneb 1600
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You can see even farther if you consider groups and clusters of stars all together. The following objects are easily visible in a telescope, and may be glimpsed with binoculars or (in the case of M31) even your naked eye. Can you find them? We'll have telescopes pointed to them at various times tonight. Again, ask an astronomer to show you where they are....
Object Distance (light years)
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Dumbbell Nebula M27 1,300
Globular Cluster M13 25,000
Globular Cluster M15 34,000
Andromeda Galaxy M31 2,900,000
Triangulum Galaxy M33 3,000,000
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