Sidereus Nuncius, 1610

Title page of Galileo Galilei, Sidereus Nuncius (1610).

What Galileo observed through his improved telescope merited immediate publication. Already in August 1609, the English mathematician Thomas Harriott (1560-1621) had penned the first known telescopic image of the moon. Galileo was not one to let the prize of priority slip through his fingers: on 13 March 1610 -- scarcely two months after his series of observations began, and only 11 days after they ended -- he published in Venice an instant scientific classic under the following title (in van Helden's English translation):

SIDEREAL / MESSENGER / unfolding great and very wonderful sights / and displaying to the gaze of everyone, / but especially philosophers and astronomers, / the things that were observed by / GALILEO GALILEI, / Florentine patrician / and public mathematician of the University of Padua, / with the help of a SPYGLASS / lately devised by him, about the face of the Moon, countless fixed stars, / the Milky Way, nebulous stars, / but especially about / FOUR PLANETS / flying around the star of Jupiter at unequal intervals and periods / with wonderful swiftness; which, unknown by anyone / until this day, the first author detected recently / and decided to name / MEDICEAN STARS

Galileo Galilei, Sidereus Nuncius, trans. Albert Van Helden (University of Chicago, 1989), p. 26.

Image credits: Courtesy of the History of Science Collections, University of Oklahoma Libraries; Copyright: the Board of Regents of the University of Oklahoma; available here. The autograph inscription records Galileo's gift of this copy to the Italian poet Gabrielle Chiabrera.

Additional resources.

High-resolution images of the complete copy in the Smithsonian are available on archive.org.
Open access copies of the full text in the 1880 translation are available here and here.