Assertion: planet's moon | /r/HasProperty | io
Facets:
Source sentences:
text: Imagine Galileo peering up at Jupiter through his small telescope only to find four moons (Io, Europa, Ganymede, and Callisto) orbiting around it, the first proof we did not live in a geocentric universe.
text: The four largest moons of Jupiter, called Io, Europa, Ganymede and Callisto, were discovered by Galileo Galilei .