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 May 27
The picture shows the planet Neptune and its moon Triton,
both in crescent phases, as captured by the passing Voyager
2 spacecraft in 1989.
Please see the explanation for more detailed information.

Crescent Neptune and Triton
Image Credit: NASA, Voyager 2

Explanation: Gliding through the outer Solar System, in 1989 the Voyager 2 spacecraft looked toward the Sun to find this view of most distant planet Neptune and its moon Triton together in a crescent phase. The elegant image of ice-giant planet and largest moon was taken from behind just after Voyager's closest approach. It could not have been taken from Earth because the most distant planet never shows a crescent phase to sunward eyes. Heading for the heliopause and beyond, the spacecraft's parting vantage point also robs Neptune of its familiar blue hue.

Tomorrow's picture: an unexpected moon


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