Io is the innermost of the four large moons of Jupiter discovered by Galileo Galilei in January 1610, using one of the early telescopes. Galileo's observations showed small points of light changing position beside Jupiter from night to night, proving that these bodies circled that planet and not the Earth. This was an important piece of evidence against the idea that everything in the heavens revolves around the Earth. The German astronomer Simon Marius claimed to have seen the moons independently and proposed the names that are now used. Io is the most volcanically active body in the solar system, heated by tidal forces from Jupiter and the other large moons, and its surface is covered with sulfur compounds and lava.
Before and after
- 1609Kepler publishes Astronomia Nova
- from 7 March 1609 to 5 April 1609Invasion of Ryukyu
- from May 1609 to October 1646Anglo-Powhatan Wars
- from 29 September 1609 to 13 June 1611Siege of Smolensk
- 7 January 1610Discovery of Io
- 7 January 1610Discovery of Callisto
- 7 January 1610Discovery of Europa
- 7 January 1610Discovery of Ganymede
- 7 January 1610Galileo discovers the moons of Jupiter
More in Universe & space
- 11 November 1572Tycho's Supernova
- 1576Founding of Uraniborg
- October 1604Kepler's Supernova appears in the constellation Ophiuchus
- 25 March 1655Discovery of Titan
- 23 December 1672Discovery of Rhea
- 9 December 1743Discovery of Great Comet of 1744
The era
This moment belongs to the Early modern world (1500 CE to 1760 CE), voyages, printing and new ideas. You can also browse everything in the 17th century.