Getting to Know Jupiter, the Gas Giant

From the lecture Series: A Field Guide to the Planets

By Sabine Stanley Ph.D., John Hopkins University

Jupiter is a gas giant and the biggest planet in our solar system. Everything in the Jupiter scale is significantly greater than Earth, except for the density. Lacking a rocky surface and, in fact, no surface does not affect the planet’s forces, winds, and hurricanes. After all, Jupiter wanted to compete with the Sun someday.

The illustration of Jupiter and its moons.
Jupiter is a gas giant and hundreds of times bigger than Earth. It is more massive than all the planets combined in the solar system. (Image: Dotted Yeti/Shutterstock)

Basic Characteristics of Jupiter

The biggest planet in our solar system is Jupiter. We call this planet a gas giant because it is primarily made of hydrogen and helium. The planet has the highest mass in the solar system—greater than all the other planets in the solar system combined.

Jupiter is located 5.2 Earth-distances from the Sun, orbiting it every 12 Earth years. Compared to what we see from Earth, the Sun looks five times smaller and 27 times fainter from Jupiter.

As we approach Jupiter, we begin to see some of its striking features in its atmosphere. First, alternating bands of white and brown horizontal bands appear. If we watch them over time, we see that they move east and west like giant jet streams. We also see a giant reddish swirling oval in the southern hemisphere, the famous Great Red Spot. As we get closer to the planet, even more details become visible in the atmosphere, resulting from turbulent winds, storms, and clouds.

Jupiter’s diameter is 11 times Earth’s diameter, making it 1331 times larger than Earth in volume. As it is a gas giant, its density is 24% of Earth’s. Thus, its mass is 318 times greater than Earth and all the other solar system planets combined, but only 1330 kilograms per cubic meter. Jupiter’s density under standard pressure and temperature would be 13,000 times lower than its average actual density. The density is mainly due to the internal pressures rather than Jupiter’s composition.

This is a transcript from the video series A Field Guide to the Planets. Watch it now, on The Great Courses Plus.

Jupiter’s Composition

An image of the satellite Juno  orbiting Jupiter.
Jupiter’s composition is very similar to
the Sun. Just like the Sun, Jupiter lacks a solid surface.
(Image: Vadim Sadovski/Shutterstock)

Jupiter is sometimes called a failed star, as it has a very similar composition to the Sun, but did not grow large enough to be one. About 80 Jupiter masses are needed for the hydrogen fusion to begin in a dwarf star—90% smaller than the Sun.

Another similarity with the Sun is that Jupiter lacks a solid surface, too. Scientists consider a surface level for comparison, where pressure equals one bar, like the atmospheric pressure on Earth.

Pressure and Gravity on Jupiter

On Earth, one bar brings along a gravitational acceleration of 9.8ms2, while on Jupiter, it results in 25ms2 gravitational acceleration. Despite Jupiter’s enormous mass, its huge volume makes gravitational acceleration less than expected. Hence, gravity on Jupiter is between 21/2 to 31/2 times greater than gravity on Earth’s surface.

Descending toward the center of Jupiter, the planet increases gravity. However, as the significant mass above has no gravitational influence anymore and the gravity begins to lower again after a certain level.

Learn more about Saturn and the rings: gravity’s masterpiece.

Jupiter’s Atmosphere

The most significant feature of Jupiter’s atmosphere is the white and brown bands around the planet and the giant storms. The colors are because of the few atoms of heavier material among hydrogen and helium. Ammonia clouds create the white, and sulfur-rich compounds create the brownish-red color. Water clouds also can be found deeper in the atmosphere.

The clouds form when gas elements reach their dew point in the atmosphere. Like all other planets, Jupiter gets cooler further away from the core due to lower pressure. The ammonia and sulfur compounds reach their dew point at the altitudes where clouds can be seen. The white clouds are higher above, and the red-brown clouds are lower in the atmosphere.

Some horizontal bands result from fluids rapidly rotating. The rotation of the planet helps to organize the movement of the atmosphere, resulting in latitudinal bands of winds. The Great Red Spot is one of the tremendous results.

Jupiter’s Great Red Spot

The Great Red Spot is a giant oval storm as big as the Earth, at a latitude of 22° south. Spinning at over 250 miles per hour at its fastest spots, the storm had been observed in 1830. It might even have been observed in the 1600s. However, it is not an eternal spiraling eye on Jupiter.

An image of Jupiter, the giant planet in the solar system.
The Great Red Spot is as big as the Earth and keeps changing its position. (Image: Nostalgia for Infinity/Shutterstock)

Great Red Spot has been changing since it was spotted. Sometimes it looks more red or brown, showing the new material it spins around. Nonetheless, if it keeps shrinking with the same rate it has so far, it will disappear in about 70 years. There are other giant storms as well.

Learn more about Jupiter’s planetlike system of moons.

Giant Storms on Jupiter

Giant storms are not unique on Jupiter. The white oval storms spotted all over Jupiter, sometimes merge and form a bigger storm. For example, from 1998 to 2000, three of them joined and shaped a mega-storm called Oval BA. Oval BA later changed color to slightly red and was thus called Red Spot, Jr.

Jupiter, the gas giant or the failed star, is a world of winds and storms and maybe no solid core!

Common Questions about Jupiter, the Gas Giant

Q: Is Jupiter a gas giant?

Jupiter is mainly made of gas at different phases. The main composition of Jupiter, the gas giant, is of hydrogen and helium. Hydrogen behaves differently under different pressures and temperatures on Jupiter—from roughly gas to liquid metal.

Q: Can you stand on Jupiter?

No. Jupiter is a gas giant, which means it is huge, but it is made of gas, and there is no hard surface to land or stand on.

Q: Is Jupiter a failed star?

Jupiter is sometimes called a failed star because it is made up of the same elements as the Sun. However, it did not get big enough when it was forming, so it ended up as a gas giant, not a star.

Q: Is there oxygen on Jupiter?

Yes. Jupiter, the gas giant, is primarily made of helium and hydrogen. However, the planet is huge enough to contain other elements as well, such as oxygen and carbon.

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