What is the Latin title of Galileo's 1610 book on his telescopic discoveries?

The Latin title of Galileo’s 1610 book was Sidereus Nuncius.

Usually translated as The Starry Messenger or Sidereal Messenger, Sidereus Nuncius was published in Venice on 13 March 1610. It was a short astronomical treatise based on Galileo’s observations through an improved telescope and became one of the most influential scientific publications of the early modern period.

The book described the Moon’s rough, mountainous surface, large numbers of previously unseen stars, and four objects circling Jupiter. Those objects are now known as Io, Europa, Ganymede, and Callisto. Galileo initially called them the Medicean Stars in honor of the powerful Medici family, hoping to secure their patronage.

The title is sometimes translated differently because the Latin word nuncius can mean either “messenger” or “message.” The quiz asks for the Latin title, however, so Sidereus Nuncius is the canonical answer. Astronomia Nova, Principia, and De Revolutionibus are different works by other scientists.