March 13, 1610

Sidereus Nuncius

First publication of Galileo's Sidereus Nuncius

The dedication was dated 12 March. By the next day, newly printed copies were already on their way to two royal courts.

13 March 1610: a booklet appears in Venice

Sidereus Nuncius appeared in Venice on 13 March 1610, issued by Tommaso Baglioni. It was the first printed scientific work founded on observations made with a telescope.

Galileo dedicated it to Cosimo II de' Medici and named Jupiter's four attendants the Medicean Stars. The printed dedication is dated at Padua on 12 March, the day before the book appeared.

What the pages showed

The booklet reported observations of the Moon's uneven surface, stars previously invisible to the naked eye, the Milky Way and nebulous objects, and four bodies revolving around Jupiter.

Its charts were crowded with new objects: 36 telescopic stars drawn around the six familiar naked-eye stars of the Pleiades, and 80 more near Orion's Belt and Sword alongside 9 already known. Galileo put the height of one lunar prominence at more than four Italian miles.

Copies on the road the same day

On 13 March Galileo sent a freshly printed copy to Cosimo. The same day Sir Henry Wotton, England's ambassador in Venice, dispatched another to King James I.

The whole first edition came to 550 copies. Eleven days separated the end of the reported observing series from publication — printing had begun while Galileo's observations of Jupiter were still going on.

Sources

Researched 23 Aug 2026 7 sources 2 audit passes

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

What the sources leave uncertain

The strongest evidence for public appearance supports March 13: Wotton’s dated dispatch says the work appeared that day. The dedication is dated March 12, and some institutional accounts use March 12 as the day printing was completed; these refer to adjacent stages of production rather than necessarily conflicting publication events.
“Starry Messenger,” “Sidereal Messenger,” “Sidereal Message” and similar renderings are defensible translations of Sidereus Nuncius; scholarship notes deliberate ambiguity in nuncius between a messenger and a message or report.