7th » Galileo Galilei makes his first observation of the four Galilean moons: Ganymede (moon) Ganymede, Callisto (moon) Callisto, Io (moon) Io and Europa (moon) Europa, although he is not able to distinguish the last two until the following day.
Famous Birthdays on January in 1610
13th » Archduchess Maria Anna of Austria (1610–1665) named Archduchess Maria Anna of Austria (d. 1665)
21st » Elizabeth Fones, English-American settler (d. 1673)