How Long is a Year on Jupiter

Article Updated: 24 Dec , 2015

The answer to ”how long is a year on Jupiter” is 11.86 Earth years. There is so much more to know about the Jovian system, that we can not just leave you with one fact, so here are some more interesting facts about Jupiter.

At perihelion Jupiter is 741 million km from the Sun(4.95 AU). At aphelion it is 817 million km from the Sun(5.46 AU). That gives Jupiter a semi-major axis of 778,340,821 km. Jupiter’s orbit varies by 76 million km, but it has one of the least eccentric orbits in the Solar System.

Jupiter has 2.5 times the mass of all of the other objects in the Solar System except the Sun. It is so massive that if it gained any more mass it would shrink. Gravitational compression would take over making the planet more dense instead of larger.

There are some conspiracy theorists who like to propose that Jupiter will become a star and destroy Earth. That can never happen. Jupiter would have to accrete about 80 times more mass than it has now and experience a huge increase in temperature in order to ignite fusion. The planet has the hydrogen it needs, but not the wherewithal to fuse it into helium and become a star.

Earth’s magnetic field is generated by its core through a dynamo effect. Scientist are not even sure that Jupiter has a rocky/metallic core, yet the planet has a magnetic field that is 14 times stronger than Earth’s. Astronomers think the magnetic field is generated by the churning of metallic hydrogen near the center of Jupiter. This magnetic field traps ionized particles from the solar wind and accelerates them to nearly the speed of light.

One of the most well known aspects of Jupiter is the Great Red Spot. Astronomers have been documenting it for nearly 350 years. It seems to grow and shrink over time. It is actually a giant storm that would totally engulf the Earth. At one time the storm covered an area that was 40,000 km long. It is slowly getting smaller, but astronomers do not know if it will ever disappear.

Knowing the answer to ”how long is a year on Jupiter” is just one minor detail about the planet. The others above are just a few facts that do not even scratch the surface of the Jovian mystery. None of Jupiter’s 67 moons or it ring system have been mentioned. Imagine the stories yet to be told.

Here’s a great image of Jupiter, captured by amateur astronomer Mike Salway, and an interesting hypothetical article about how Jupiter’s orbit could mess up the Solar System.

Here’s some general information on Jupiter from the Nine Planets, and more information from Solar Views.

We’ve also recorded an entire show just on Jupiter for Astronomy Cast. Listen to it here, Episode 56: Jupiter, and Episode 57: Jupiter’s Moons.


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