Sir

It is commonly accepted that Galileo in 1609 was the first to appreciate the discrete nature of the stars in the Milky Way, by training his telescope on that part of the heavens. Your review of Francesco Bertola's book Via Lactea (Nature 427, 489; 200310.1038/427489b) notes Bertola's suggestion that the true nature of the Milky Way may have been known before Galileo's observation.

There is evidence to support this view. Sonnet 31 of Thomas Watson's Hekatompathia (1582) describes the Milky Way as being composed of a huge number of discrete stars: “That can not tell how many starres appeare/In part of heav'n, which Galaxia hight” — “Galaxia” is identified as the Milky Way in the notes to the poem. Sonnet 31 also appears in an earlier version of the Hekatompathia called Looking glase for Loouers. Watson, it seems, knew of the discrete nature of the stars before 1582.

Sebastian Verro also describes the Milky Way as a collection of discrete stars in his 1581 Physicorum Libri X, Book II, chapter 17, page 31: “We now refer to the glorious Galaxia, which is also called the Milky Way. It is a chaos of minute, brightly shining stars, as if a fog or mist, which traverses the sky in an oblique path” (our translation).

Perhaps Watson and Verro gained their knowledge of the Milky Way through the use of earlier instruments than Galileo's telescope, such as the perspective glasses of the sixteenth-century English natural scientists Leonard and Thomas Digges.