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.

2022 January 23
The featured image shows Saturn, its rings nearly edge-on,
shadows of its rings on the planet's face, and the ice-moon
Tethys. The image was taken by Cassini in 2005.
Please see the explanation for more detailed information.

Saturn, Tethys, Rings, and Shadows
Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

Explanation: Seen from ice moon Tethys, rings and shadows would display fantastic views of the Saturnian system. Haven't dropped in on Tethys lately? Then this gorgeous ringscape from the Cassini spacecraft will have to do for now. Caught in sunlight just below and left of picture centre in 2005, Tethys itself is about 1,000 kilometres in diameter and orbits not quite five saturn-radii from the centre of the gas giant planet. At that distance (around 300,000 kilometres) it is well outside Saturn's main bright rings, but Tethys is still one of five major moons that find themselves within the boundaries of the faint and tenuous outer E ring. Discovered in the 1980s, two very small moons Telesto and Calypso are locked in stable along Tethys' orbit. Telesto precedes and Calypso follows Tethys as the trio circles Saturn.

Tomorrow's picture: witch star?


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