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 April 27
The featured image shows the planet Jupiter as
seen by NASA's passing robotic spaceship Juno. A large
dark spot seen on Jupiter is the shadow of Jupiter's
moon Io.
Please see the explanation for more detailed information.

Moon Shadow on Jupiter
Image Credit: NASA/JPL-Caltech/SwRI/MSSS; Processing & License: Thomas Thomopoulos

Explanation: What is that large dark spot on Jupiter? It's the shadow of Ganymede, Jupiter's largest moon. When Jupiter's moons cross between the Jovian giant and the Sun, they created shadows just like when the Earth's moon crosses between the Earth and the Sun. Also like on Earth, if you were in a dark shadow on Jupiter, you would see a moon completely eclipse the Sun. Unlike on Earth, moon shadows occur most days on Jupiter -- what's more unusual is that a spacecraft was close enough to record one with a high-resolution image. That spacecraft, Juno, was passing so close to Jupiter in late February that nearby clouds and the dark eclipse shadow appear relatively large. Juno has made many discoveries about our Solar System's largest planet, including, recently, rapidly expanding circular auroras.

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