Italian astronomer Galileo discovered that millions of stars are not visible to the naked eye.
The first objects he discovered by means of a telescope were then four brightest moons of Jupiter, known now as the Galilean satellites.
They were subsequently named by German astronomer Simon Marius after Greek mythological figure who were closely associated with Jupiter – Io, Europa, Ganymede and Callisto.
Other notable events on January 7th:
In 2015, two gunmen connected al-Qaeda stormed the Paris Charlie Hebdo offices, killing 12 people in revenge of the magazine’s satirical portrayals of the Prophet Muhammad.
In 2003, by presidential decree, Christmas (which falls on this day on the Coptic Orthodox calendar) was celebrated for the first time as a national holiday in Egypt, a country almost entirely Muslim.