The images above are of Jupiter and its four Galilean moons. The image of Io is moving toward the image of Jupiter and the two will eventually merge. Io is the innermost Galilean satellite of Jupiter and the only one with active volcanoes.

In the image on the right, taken only 25 minutes after the left one, notice how the separation between Io and Jupiter has decreased. This is what Galileo also noticed when he looked through his crude telescope in the year 1610. He established that these moons orbited the parent planet. This discovery violated the ancient philosophies of an idealized universe with Earth as the center of all motion.

Image Information: 22:45 and 23:10 on February 13, 2002. The exposure time for each image was .01 second.

Telescope and Camera Information: 10in. f/6.3 Meade Schmidt-Cassegrain with an Apogee AP6E CCD camera.

Jupiter and its four Galilean moons.