Since this could so easily turn into a Sagan quote fest, since he had an enormous number of wonderful and eloquent quotes, I think we should focus on finding quotes from people OTHER than Sagan. Not as fun or as easy, I know, but we really should have quotes from a diverse range of people.
I agree completely; no more Sagan's quote from me, then. Here are more quotes that I got from
http://www.spacequotations.com/search.html, the site that SpaceEngineer referred in first post:
The moon is the first milestone on the road to the stars. — Arthur C. Clarke
Our sun enlightens the planets that belong to him; why may not every fixed star also have planets to which they give light? — Bernard Le Bovier de Fontenelle, A week's conversation on the plurality of worlds, 1686. (English translation by William Gardiner, 1728.)
I will love the light for it shows me the way; yet I will love the darkness for it shows me the stars. — Augustine "Og" Mandino, 'The Scroll Marked II,' The Greatest Secret in the World, 1972
Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case the idea is quite staggering. — Arthur C. Clarke
We know the number of stars in the universe is something like one followed by 23 zeros. Given that number, how arrogant to think ours is the only sun with a planet that supports life, and that it's the only solar system with intelligent life. — Edward J. Weiler, NASA Director, Washington Post newspaper, 20 July 2008
Equipped with his five senses, man explores the universe around him and calls the adventure Science. — Edwin Hubble, The Nature of Science, 1954
In my studies of astronomy and philosophy I hold this opinion about the universe, that the Sun remains fixed in the centre of the circle of heavenly bodies, without changing its place; and the Earth, turning upon itself, moves round the Sun. — Galileo Galilei, letter to Cristina di Lorena, Grandduchess of Tuscany, 1615.
There is in the universe neither center nor circumference. — Giordano Bruno, 'On the Infinite Universe and Worlds,' 1584
Now my own suspicion is that the Universe is not only queerer that we suppose, but queerer than we can suppose. — J. B. S. Haldane, Possible Worlds, 1927.
The universe is wider than our views of it. — Henry David Thoreau, Walden, 1854.
We should do astronomy because it is beautiful and because it is fun. We should do it because people want to know. We want to know our place in the universe and how things happen. — John N. Bahcall, Sky and Telescope magazine, January 1990
Astronomy is the science of the harmony of infinite expanse. — John Russell
The site actually has a nice collection of space-related quotes; too bad it can only show 50 results maximum for a keyword. The above quotes are searched using the keyword "star", "stars", "universe", and "science". If you want to contribute but don't know where to search, perhaps you can try to search on the site with other keywords, so we don't search for the same thing twice. But of course feel free to redo what I did if you are skeptical about my selection.