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 "Io," third largest moon of Jupiter 46" x 32" |
 "Trifid Nebula, M20" 44" x 36" |
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| The planet Jupiter's four largest moons are called the Galilean satelites, after Italian astronomer Galileo Galilei, who observed them in 1610. These large moons, named Io, Europa, Ganymede, and Callisto, are each distinctive worlds. Io is the most volcanically active body in the solar system. Its surface is covered by sulfur in different colorful forms. As Io travels in it's slightly elliptical orbit, Jupiter's immense gravity causes tides in the solid surface 100 meters (300 feet) high on Io, generating enough heat to give rise to the volcanic activity and drive off any water. Io's volcanoes are driven by hot silicate magma. |
M20, the Trifid Nebula is a remark complex of red emission and blue reflection nebulosity about the size of the full moon, intersected by three dark lanes, from which the Trifid gets it's name. M21 is a rich open cluster comprised of some 70 stars with a large brightness range and strong central condensation, and is located in the constellation Sagittarius. Click on Thumbnail for enlarged view. |
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