Astronomy Picture of the Day

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

2010 January 27
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Tethys Behind Titan
Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA

Explanation: What's that behind Titan? It's another of Saturn's moons: Tethys. The robotic Cassini spacecraft orbiting Saturn captured the heavily cratered Tethys slipping behind Saturn's atmosphere-shrouded Titan late last year. The largest crater on Tethys, Odysseus, is easily visible on the distant moon. Titan shows not only its thick and opaque orange lower atmosphere, but also an unusual upper layer of blue-tinted haze. Tethys, at about 2 million kilometers distant, was twice as far from Cassini as was Titan when the above image was taken. In 2004, Cassini released the Hyugens probe which landed on Titan and provided humanity's first views of the surface of the Solar System's only known lake-bearing moon.

Tomorrow's picture: open space

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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