Jupiter's Galilean Moons
Images: Galileo Project, Voyager Project
These four largest and brightest moons of Jupiter, first discovered by Galileo Galilei in 1610, are known as the Galilean satellites. Starting from left to right the moons are Io, Europa, Ganymede, and Callisto. This order is also the order of increasing distance from Jupiter.
These are big moons that attend the largest planet. The smallest of the lot, Europa, is the size of Earth's moon while Ganymede is the largest moon in the Solar System. In fact, Ganymede with a diameter of 3,100 miles, is larger than the planet Mercury. Battered Callisto's image was recorded during the 1979 flyby of Voyager. The other portraits were taken by the Galileo spacecraft, which began exploring the Jovian system in 1995.
Every six years the Earth lies in the orbital plane of Jupiter's moons. At this time Jupiter's 4 bright moons are directly in our line of sight, and the shifting of these moons, one in front of another, plus their shadows crossing the surface of Jupiter grab the attention of those with telescopes. The last time this occurred was in 2003. Once again in 2009 Earth is moving through the plane of Jupiter's satellites, allowing the moons to line up in their special 6-year geometry.
Between April and December of 2009, observers around the world can see Jupiter's moons passing one in front of another as they circle the giant planet. As part of the International Year of Astronomy, professional astronomers are organizing a worldwide observing campaign to record as many of these events as possible. Click here for details. spaceweather.com 5/10/09
High-resolution images of the phenomena are now possible with the vast improvement of imaging techniiques and equipment since 2003.
Watch Europa cccult Ganymede, Ganymede occult Europa and Ganymede Occult Io.
Whenever you think of Jupiter, think "I eat green caterpillars." Why?
Well, with a cheap telescope or even a pair of binoculars you can watch the four largest of Jupiter's 40 moons [63 moons update] as they change position from night to night. They'll look like tiny pinpoints of light although three of them are actually larger than our Moon. Their names are Io, Europa, Ganymede and Callisto and when they're all lined up together on one side of Jupiter the phrase 'I Eat Green Caterpillars' will help you remember their order out from Jupiter. I for Io, E for Europa, G for Ganymede and C for Callisto. It's fun to watch them change position … from night to night. Happy green caterpillaring and Keep Looking Up! Star Gazer
Jupiter’s Moons
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