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Primary sourceBook1610

Sidereus Nuncius

Galileo Galilei · 1610

Galileo's 1610 pamphlet reporting his first telescope observations of the Moon, countless stars and Jupiter's moons.

Galileo's own report of his first telescope discoveries, the work that made him famous.

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Title page of the 1610 Latin book Sidereus Nuncius by Galileo Galilei, printed in Venice by Thomas Baglionus. Black text in several type styles, with a central woodcut emblem of a seated figure in an oval frame flanked by cherubs. Handwritten shelfmark appears at the bottom.
Galileo Galilei, Sidereus Nuncius, title page, 1610. Houghton Library, Harvard University.

About this source

What it is

Sidereus Nuncius (the 'Starry Messenger') is a short treatise published by Galileo Galilei in Latin in March 1610, printed in Venice. It was the first published scientific work based on telescope observations.

Why it matters

The book reported mountains on the Moon, thousands of previously invisible stars, and four moving 'stars' near Jupiter that Galileo realised were its moons. These findings undermined the old Aristotelian idea of a perfect unchanging heaven centred on Earth, and made Galileo instantly famous across Europe.

Look closer

  • Why would drawings and diagrams matter so much in a book reporting new discoveries?
  • What does the decorative title page tell you about how books were made and sold in 1610?
  • How might Galileo's rivals have reacted to such bold claims before anyone else could repeat his observations?

This book is part of the curated material that grounds the AI version of Galileo Galilei, Nicolaus Copernicus and Johannes Kepler on Humy.ai — when students ask about related events, the AI can quote it and cite it.

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Engraved oval portrait print of a bearded older man with receding hair, wearing a white collar and a buttoned dark coat, in an oval frame. Inscribed 'Galileus Galileus Florentinus' at top, 'Eques Octavius Leonus' and 'Romanus pictor fecit' at bottom, and dated '16 24' with 'Superiorum licentia'. Printed on cream paper with a grayscale color scale at right.Painting

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Portrait of Galileo Galilei (1624 print)

1624

Oil portrait of an elderly bearded man with a white collar, wearing a black robe, seated at a table with books, a pair of dividers in his raised hand, and a celestial globe to the left, in a dark background. A brass plaque on the frame reads Galileo Galilei.Painting

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Oil Portrait of Galileo in His Study

Unknown Italian painter · 18th century (?)

Oval-framed line engraving of an older bearded man in a large white collar and dark doublet, with a Latin inscription above reading Galileus Galileus Florentinus, and an artist credit below. Handwritten Italian caption on mount beneath.Painting

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Galileo Galilei, line engraving by Ottavio Leoni

Ottavio Leoni · 1624

Title page of the 1632 Florentine edition of Galileo Galilei's Dialogo, printed in large serif capitals with a decorative woodcut emblem, imprint 'In Fiorenza, Per Gio: Batista Landini MDCXXXII', and several library stamps and handwritten shelf marks.Book

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Dialogue Concerning the Two Chief World Systems

Galileo Galilei · 1632

Title page of a printed book reading 'Lettera del Signor Galileo Galilei Accademico Linceo scritta alla Granduchessa di Toscana', with a decorative floral woodcut ornament and the imprint 'In Fiorenza, MDCXX' at the bottom.Letter

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Letter to the Grand Duchess Christina

Galileo Galilei · 1615

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