Galileo sketches of faint stars
Sketches of faint stars in the Orion constellation, as seen by Galileo through his telescope. The larger stars with a central dots are those visible to the naked eye, with the topmost three corresponding to the so-called beltof Orion. That the universe contained many more stars than previously known gave moral support to the idea that it may also be a lot larger than assumed up to then. This idea had been advanced by Copernicus himself, as a possible explanation for the lack of observed annual parallax in the fixed stars. Reproduced from Galileo's 1610 Sidereus Nuncius.
Bibliography:
Galileo, G. 1610, Sidereus Nuncius, trans. A. Van Helden 1989,The University of Chicago Press.