Jupiter's four brightest satellites (moons) - namely Ganymede (magnitude +4.6), Io (+5.0), Europa (+5.3) and Callisto (+5.6) - can be seen through telescopes or steadily-held binoculars. The satellites are seen to change their position in relation to each other, along the planet's equatorial plane, from one night to the next. In fact, their motion can be detected in the space of just a few hours.

This Java applet shows Jupiter and the four satellites in their present positions. Their distances from Jupiter are shown in correct proportion to that of the real Jovian system. North is up and East is to the left, matching the Northern hemisphere view; Southern hemisphere observers will need to invert the image to obtain the correct view.

The left-to-right order of the displayed satellites are indicated by the satellite names in the lower left box. If the name is in red, it indicates that the satellite is being occulted by Jupiter (i.e. it is passing behind the planet). If the name is in yellow, the satellite is passing in front of Jupiter (an event known as a transit). Satellite transits can be observed in larger telescopes, the satellite appearing as a small black dot moving slowly against Jupiter's bright disk.

Because of their low magnification, binoculars may have some difficulty detecting Io since it is the closest of the four satellites to Jupiter; it never lies more than three Jupiter-diameters away. Europa is easier, but Ganymede is the easiest of the four to see. Callisto moves furthest away from the planet, but it is also the faintest of the four.