In what year was Jupiter discovered?

There is no known date for the discovery of Jupiter nor any known person who discovered the planet. Jupiter is one of the five planets visible to the naked eye from Earth. Because of its visibility, Jupiter has been studied since ancient times.

In 1610, Galileo first discovered that Jupiter had four large moons: Io, Europa, Ganymede and Callisto. In the 1660s, Cassini saw Jupiter's bands and its Great Red Spot and also determined the planet's rotational period. In 1973, NASA launched Pioneer 10, the first spacecraft to visit Jupiter. NASA's Galileo mission, which went into orbit in 1995, is the only spacecraft to orbit Jupiter.