On January 7, 1610, physicist and astronomer Galileo Galilei turned his new telescope to the nocturnal sky to watch the planet Jupiter and discovered the eponymous four moons of Jupiter, Io, Europa, Ganimede, and Callisto.
On this day in 1994, the last parts of the comet Shoemaker-Levy 9 collided with the largest planet within our solar system, Jupiter. This was the first time, that an extraterrestrial collision of two objects could be directly observed.