Image credit: NASA

Which planet is photographed in this image?

This picture features none other than the big brother of our solar neighborhood, Jupiter.

This picture was taken by the Galileo spacecraft, which orbited the planet from 1995 to 2003. The Jovian ring system was originally discovered by the passing Voyager 1 spacecraft in 1979. Voyager 2 was then reprogrammed to take more comprehensive pictures and confirmed the discovery. Later data from Galileo showed that these rings were created by meteor impacts on some of the planet’s nearby moons (primarily Adrastea and Metis). Normally, when meteors impact and eject this kind of debris, it falls back onto the body it originally came from (just like it did for Earth’s moon). Because Jupiter has such a strong gravitational pull, this dust instead formed a very faint ring system.

Clues:

So, what are some clues identifying this planet? Not a lot actually.

Since the planet obviously has a ring system, it’s one of the gas giants. Uranus is tilted on its side relative to the plane of the solar system, which means you would be looking at the ring system face-on rather than edge-on if this were a picture of Uranus. (Sssuming the picture hasn’t been rotated, but I’d say it’s a reasonably safe assumption to make.)

For that matter, both Neptune and Uranus have only been visited by the Voyager 2 spacecraft, and the spacecraft only conducted a flyby. Setting up for this type of picture isn’t an easy task. It also helps that Voyager 2’s flight path didn’t create the right alignment to take this type of picture.

This simply leaves Saturn and Jupiter. In comparison to their host planet, Saturn’s rings are very long (in this case, I’m using the phrase to mean the diameter of the rings is long in comparison to the diameter of Saturn). Jupiter’s ring system appears much shorter because the planet is much larger. Jupiter also has very little axial tilt, so its ring system is aligned in edge-on with the Sun.

Thus, I would say it’s a reasonable assumption to say the planet picture is Jupiter.


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