Fun Facts About Jupiter, the Biggest Planet

How big is Jupiter?

Jupiter is the fifth planet from the Sun and the largest planet in the solar system. NASA says it's about 11 times wider than Earth, and if it were a hollow shell, about 1,000 Earths could fit inside. Jupiter has more than twice the mass of all the other planets combined. NASA's comparison: if Earth were the size of a grape, Jupiter would be about as big as a basketball.

Jupiter is also the oldest planet, formed about 4.6 billion years ago, and it's bright in our night sky, often outshining every star. It's named after the king of the Roman gods.

Jupiter by the numbers

Source: NASA Planetary Fact Sheet and NASA Science.

Jupiter has the shortest day of any planet: it spins once in under 10 hours. That fast spin makes it bulge at the equator and stretches its clouds into stripes. Its year is about 12 Earth years, so a 12-year-old on Earth would be about 1 in Jupiter years.

A planet made of gas

Jupiter is a gas giant, made mostly of hydrogen and helium, the same ingredients as the Sun. It has no solid surface. Tap the cutaway to explore what's inside:

1. Cloud tops: three cloud layers, ammonia ice on top, ammonium hydrosulfide in the middle and water at the bottom, together about 71 kilometers thick.
2. Liquid hydrogen: going deeper, the gas gets so squeezed that hydrogen becomes a liquid, making the largest ocean in the solar system (not a water ocean).
3. Metallic hydrogen: deeper still, NASA says, hydrogen becomes electrically conducting like a metal. Its churning creates Jupiter's magnetic field, 16 to 54 times as powerful as Earth's.
4. Fuzzy core: NASA's Juno spacecraft found the core is larger than expected and partly dissolved, with no sharp edge, a "dilute" or "fuzzy" core.

Jupiter has star-like ingredients but never grew massive enough to start shining like a star.

Stripes and storms

Jupiter's colorful stripes are clouds blown by powerful winds, up to 539 kilometers per hour at the equator. The dark stripes are called belts and the light ones zones, and neighboring stripes blow in opposite directions. Where they meet, storms swirl.

The most famous storm is the Great Red Spot, a giant spinning storm about twice as wide as Earth that people have watched for more than 300 years. Juno's measurements show it reaches more than 350 kilometers down into the clouds. It has been shrinking over the past century, but it's still the biggest storm in the solar system.

Juno also found clusters of cyclones at the poles: eight arranged in an octagon around the north pole and five in a pentagon around the south pole.

Jupiter's moons

NASA says Jupiter has 115 officially recognized moons, plus thousands of small objects in orbit. The four biggest are called the Galilean moons, because Galileo Galilei discovered them with an early telescope in 1610. You can see them as tiny dots next to Jupiter with good binoculars.

In the 3D view, watch Io zip around Jupiter in under two days while Callisto takes more than two weeks; their speeds are real relative to each other.

Faint rings and a giant magnetic bubble

Jupiter has rings, but they're faint and dark. Voyager 1 discovered them in 1979. NASA says they're made of small dust particles, probably blasted off Jupiter's small inner moons by meteoroid impacts.

Jupiter's magnetic field traps so much radiation that spacecraft need special shielding. Its magnetic bubble, the magnetosphere, stretches up to 3 million kilometers toward the Sun, and its tail reaches as far as Saturn's orbit. It also powers bright auroras at Jupiter's poles.

Jupiter's giant gravity

Jupiter is so massive that its gravity shapes the whole solar system. Scientists think its pull stirred up the rocky pieces between it and Mars so much that they could never clump together into a planet; they're still there as the asteroid belt. Its gravity also grabs or flings away comets and asteroids that pass nearby.

In July 1994, people around the world watched a comet called Shoemaker-Levy 9, which Jupiter's gravity had torn into more than 20 pieces, crash into the planet one fragment at a time. The impacts left dark scars in Jupiter's clouds, some bigger than Earth, that lasted for months.

Missions to Jupiter

• Pioneer 10 made the first flyby in 1973. Pioneer 11 followed in 1974, and the two Voyagers in 1979.
• Galileo orbited Jupiter from 1995 to 2003 and dropped a probe into its atmosphere.
• Juno has orbited Jupiter since 2016, mapping its gravity, magnetic field, storms and fuzzy core.
• Europa Clipper launched on October 14, 2024, to study whether Europa's ocean could support life. It's due to arrive in 2030.

Fun facts about Jupiter

• If you weigh 80 pounds on Earth, you'd weigh about 189 pounds at Jupiter's cloud tops.
• Jupiter's huge gravity has pulled in or flung away many comets and asteroids over billions of years.
• Jupiter has the strongest magnetic field of any planet.
• Jupiter spins so fast that its equator bulges out by about 7 percent.

Learning about Jupiter at home

Look for Jupiter in the night sky with binoculars and try to spot the four Galilean moons; sketch their positions on several nights, just like Galileo did. Take the facts quiz above, then print the labeled Jupiter diagram.

Next, visit ringed Saturn, go back to Mars, or watch Jupiter orbit with all the others in the 3D solar system.