Astronomy Picture of the Day

Discover the cosmos! Each day we feature a different image or photograph of our fascinating universe, along with a brief explanation written by a professional astronomer.

November 3, 1995
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Jupiter's Moon Amalthea
Credit: NASA, Voyager 1, Copyright Calvin J. Hamilton

Explanation: Amalthea is Jupiter's fifth largest moon, much smaller than the four Galilean satellites Io, Europa, Ganymede, and Callisto. The orbit of Amalthea is inside of these moons, and with its long axis always pointing toward Jupiter. It's dark surface color is probably due to sulfur being expelled from Io. Amalthea is not massive enough for its internal gravity to make it spherical. Amalthea was discovered in 1892 by Edward Barnard.

Tomorrow's picture: Neptune's Moon Proteus

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