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 July 17
The featured image shows Jupiter's moon Europa in front
of Jupiter with many of Jupiter's clouds, including the Great
Red Spot, visible. Please see the explanation for more detailed information.

Europa and Jupiter from Voyager 1
Image Credit: NASA, Voyager 1, JPL, Caltech; Processing & License: Alexis Tranchandon / Solaris

Explanation: What are those spots on Jupiter? Largest and furthest, just right of center, is the Great Red Spot -- a huge storm system that has been raging on Jupiter possibly since Giovanni Cassini's likely notation of it 357 years ago. It is not yet known why this Great Spot is red. The spot toward the lower left is one of Jupiter's largest moons: Europa. Images from Voyager in 1979 bolster the modern hypothesis that Europa has an underground ocean and is therefore a good place to look for extraterrestrial life. But what about the dark spot on the upper right? That is a shadow of another of Jupiter's large moons: Io. Voyager 1 discovered Io to be so volcanic that no impact craters could be found. Sixteen frames from Voyager 1's flyby of Jupiter in 1979 were recently reprocessed and merged to create the featured image. Forty-five years ago this August, Voyager 1 launched from Earth and started one of the greatest explorations of the Solar System ever.

Free Download: Voyager Posters
Tomorrow's picture: hubble webb < | Archive | Submissions | Index | Search | Calendar | RSS | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.


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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 July 18
The featured image shows a grouping of four galaxies, some interacting, combining images from Webb, Hubble, and the Subaru telescope.
Please see the explanation for more detailed information.

Stephan's Quintet from Webb, Hubble, and Subaru
Image Credit: Webb, Hubble, Subaru; NASA, ESA, CSA, NOAJ, STScI; Processing & Copyright: Robert Gendler

Explanation: OK, but why can't you combine images from Webb and Hubble? You can, and today's featured image shows one impressive result. Although the recently launched James Webb Space Telescope (Webb) has a larger mirror than Hubble, it specializes in infrared light and can't see blue -- only up to about orange. Conversely, the Hubble Space Telescope (Hubble) has a smaller mirror than Webb and can't see as far into the infrared as Webb, but can image not only blue light but even ultraviolet. Therefore, Webb and Hubble data can be combined to create images across a wider variety of colors. The featured image of four galaxies from Stephan's Quintet shows Webb images as red and also includes images taken by Japan's ground-based Subaru telescope in Hawaii. Because image data for Webb, Hubble, and Subaru are made freely available, anyone around the world can process it themselves, and even create intriguing and scientifically useful multi-observatory montages.

Stephan's Quintet from just: Webb, Hubble
Tomorrow's picture: half star cluster

< | Archive | Submissions | Index | Search | Calendar | RSS | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.