What scientist was the first person to observe a moon orbiting a planet besides our own?
Answer Galileo Galilei
Using one of the first primitive telescopes, Galileo was able to observe small points of light that appeared to move back and forth near Jupiter. He determined (correctly) that this must mean that there are 4 objects (now known as Jupiter's Galilean moons) orbiting around Jupiter. This was an important piece of evidence to help people accept that the Earth was not the center of the universe.