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.

2023 April 30
An oblong moon is shown in very muted colors, appearing
almost gray. The background is deep space and completely dark
at this short exposure time.  
Please see the explanation for more detailed information.

Saturn's Moon Helene in Color
Image Credit: NASA, JPL-Caltech, SSI; Processing: Daniel Macháček

Explanation: Although its colors may be subtle, Saturn's moon Helene is an enigma in any light. The moon was imaged in unprecedented detail in 2012 as the robotic Cassini spacecraft orbiting Saturn swooped to within a single Earth diameter of the diminutive moon. Although conventional craters and hills appear, the above image also shows terrain that appears unusually smooth and streaked. Planetary astronomers are inspecting these detailed images of Helene to glean clues about the origin and evolution of the 30-km across floating iceberg. Helene is also unusual because it circles Saturn just ahead of the large moon Dione, making it one of only four known Saturnian moons to occupy a gravitational dimple known as a stable Lagrange point.

Tomorrow's picture: stars with colors


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