Jupiter and the Galilean Moons
When Galileo observed Jupiter through a newly improved telescope in 1610, he spotted a most unusual site: four bodies that he later determined were orbiting the giant planet. While Galileo was far from the first to propose any sort of heliocentric solar system, the moons added to the growing body of evidence that the Earth is not at the center.
Some bodies are too small for Hubble to resolve in much detail. Pluto is just a point of light to the telescope. But giant Jupiter, which isn't quite the failed star portrayed in some science fiction but which remains a behemoth of a world, can be observed. So too can the transit of the four largest moons of the 67 total orbiting bodies around the largest planet.
Three of four of the moons harbor water; two may be able to support life. Here, a composite image shows the moons transiting across the great world in progressive detail. It's a sight that can be observed with a good set of binoculars, but remains an impressive site through the eyes of Hubble.