Galileo Galilei’s Sidereus Nuncius
Alessia Tami (University of Zurich)
In 1610, Galileo Galilei’s discovery of Jupiter’s four largest moons provided further confirmation that the Earth was not the only center of motion in the universe, contrary to what the Ptolemaic system taught. Suddenly one of the seven planets known since antiquity was demonstrably not on its own in deep space.
Galileo’s observations of Jupiter’s four moons were published in 1610 in Sidereus nuncius (Starry Messenger). The publication process was rushed, as Galileo was eager to anticipate others who may also have been observing the sky with different kinds of telescopes.
Conscious of the fact that funding for science depended heavily on personal patronage, Galileo secretly wrote to the Grand Duke of Tuscany, Cosimo de Medici. He asked for the Duke’s approval to name the stars and planets he had discovered “Cosmian stars” in his honor. Printing had already begun when the Duke’s reply arrived, giving his consent to naming the stars “Medicea Sidera,” or “Medicean stars,” in recognition of the Medici family.
The slips of paper that were added to correct the stars’ name in the first editions of the Sidereus Nuncius are testimony to the complex social and financial circumstances that Galileo was navigating in order to publish his findings.