Jupiter Astronomical symbol of Jupiter
Jupiter by Cassini-Huygens.jpg
Photo of Jupiter from Cassini.
How to say it how to say: /ˈdʒuːpɨtər/
Adjective Jovian
Reference date J2000
Longest distance from the Sun 816,520,800 km (5.4581 AU)
Shortest distance from the Sun 740,573,600 km (4.9504 AU)
Longest distance from the center of its orbital path
("semi-major axis")
778,547,200 km (5.2043 AU)
How long it takes to complete an orbit 4,331.572 days
11.85920 yr
How long an orbit seems to take
(from the central body)
398.88 days
Average speed 13.07 km/s
Mean anomaly 18.818°
Angle above the reference plane
1.305° to Ecliptic
6.09° to Sun's equator
0.32° to Invariable plane
Natural things which orbit it 67
Size and other qualities
Average radius 69,911±6 km
Surface area 6.21796×1010 km²
121.9 Earths
Volume 1.43128×1015 km³
1321.3 Earths
Mass 1.8986×1027 kg
317.83 Earths
Average density 1.326 g/cm³
Surface gravity 24.79 m/s²
2.528 g
Escape velocity 59.5 km/s
Turning speed 12.6 km/s
45,300 km/h
Angle at which it turns
(in relation to its orbit)
Angle above the celestial equator
How much light it reflects

0.343 (bond)

0.52 (geom.)
Surface temp. Min. Avg. Max.
1 bar level 165 K
0.2 bar 112 K
Seeming brightness
("apparent magnitude")
-1.6 to -2.94
Pressure 20–200 kPa (cloud layer)
Scale height 27 km
87.8 to 91.8% Hydrogen (H2)
8.2 to 12.2% Helium
~0.3% Methane
~0.026% Ammonia
~0.003% Hydrogen deuteride (HD)
0.0006% Ethane
0.0004% water
ammonium hydrosulfide(NH4SH)
Jupiter diagram
Diagram of Jupiter
790106-0203 Voyager 58M to 31M reduced
A series of photographs taken by Voyager 1 as it approached Jupiter, made into an animation.

Jupiter is the largest planet in the Solar System. It is the fifth planet from the Sun. Jupiter is classified as a gas giant, both because it is so large and due to the fact that it is made up mostly of gas. The other gas giants are Saturn, Uranus, and Neptune.

Jupiter has a mass of 1.8986×1027 kg, or about 318 Earths. This is twice the mass of all the other planets in the Solar System put together.

Jupiter can be seen with the naked eye. It was known to the ancient Romans, who named it after their god Jupiter (Latin: Iuppiter). Jupiter is the third brightest object in the night sky. Only the Earth's moon and Venus are brighter.

Jupiter has at least 67 moons. Of these, 55 are very small and less than five kilometres wide. The four largest moons of Jupiter are Io, Europa, Ganymede, and Callisto. They are collectively called the Galilean moons, because they were discovered by the Italian astronomer Galileo Galilei. Ganymede is the largest moon in the Solar System. It is larger in diameter even than Mercury.


Jupiter is the biggest planet in the Solar System with a diameter of 142,984 km. This is eleven times bigger than the diameter of Earth.

PIA02863 - Jupiter surface motion animation
An animation of part of Jupiter's cloud system. The animation is made of over 40 photographs taken by the Cassini spacecraft between October 31 and November 9, 2000.
Four photographs of Jupiter taken in 1994. The bright white spots are explosions where parts of the comet Shoemaker Levy-9 hit the planet.
A picture by an artist of the Voyager 1 spacecraft that flew past Jupiter in 1979.


The atmosphere near the surface of Jupiter is made of about 88 to 92% hydrogen, 8 to 12% helium, and 1% other gases.

Further into the planet it is so hot and the pressure so high that helium becomes a liquid and precipitates or rains further down into the planet. Based on spectroscopy, Jupiter seems to be made of similar gases to Saturn. It is not as similar to Neptune or Uranus. These two planets have much less hydrogen and helium gas.

The very high temperatures and pressures in Jupiter's core mean scientists cannot tell what materials would be there. This cannot be found out, because it is not possible to create the same amount of pressure on Earth.

Above the unknown inner core is an outer core. The outer core of Jupiter is thick, liquid hydrogen. The pressure is high enough to make the hydrogen solid, but then it melts because of the heat.


Jupiter is twice as massive as all the other planets in the Solar System put together. It gives off more heat than it gets from the sun. Jupiter is 11 times the width of Earth and 318 times as massive. The volume of Jupiter is 1,317 times the volume of Earth. In other words, 1,317 Earth-sized objects could fit inside it.

Cloud layers

Jupiter has many bands of clouds going horizontally across its surface. The light parts are called zones and the darker are called belts. The zones and belts often interact with each other. This causes huge storms. Wind speeds of 360 kilometres per hour (km/h) are common on Jupiter. To show the difference the strongest tropical storms on Earth are about 100 km/h.

Most of the clouds on Jupiter are made of ammonia. There may also be clouds of water vapour similar to clouds on Earth. Spacecrafts such as Voyager 1 have seen lightning on the surface of the planet. Scientists think it was water vapour because lightning needs water vapour. These lightning bolts have been measured as up 1,000 times as powerful as those on Earth. The brown and orange colours are caused when sunlight passes through or refracts with the many gases in the atmosphere.

Great Red Spot

One of the biggest features in Jupiter's atmosphere is the Great Red Spot. It is a huge storm which is bigger than the entire Earth. It has been known about for just under 200 years and possibly even longer. Storms can last for hours or as long as hundreds of years in the case of the Great Red Spot.

Magnetic field

Jupiter has a magnetic field similar to Earth's but 11 times stronger. It also has a magnetosphere much bigger and stronger than Earth's. The field traps radiation belts much stronger than Earth's Van Allen radiation belts, strong enough to endanger any spacecraft travelling past or to Jupiter. The magnetic field is probably caused by the large amounts of liquid metallic hydrogen in the core of Jupiter. The four largest moons of Jupiter and many of the smaller ones orbit or go around the planet within the magnetic field. This protects them from the solar wind. Jupiter's magnetic field is so large, it reaches the orbit of Saturn 7.7 million miles (12 million km) away. The Earth's magnetosphere does not even cover its moon, less than a quarter of a million miles (400,000 km) away.

Ring system

Jupiter also has a thin planetary ring system. These rings are very difficult to see, and so they were not discovered until NASA's Voyager 1 probe went to Jupiter in 1979. There are four parts to Jupiter's rings. The closest ring to Jupiter is called the Halo Ring. The next ring is called the Main Ring. It is about 6,440 km (4,002 mi) wide and only 30 km (19 mi) thick. The Main and Halo rings of Jupiter are made of small, dark particles. The third and fourth rings, called the Gossamer Rings, are transparent (see through) and are made from microscopic debris and dust. This dust probably comes from small meteors striking the surface of Jupiter's moons. The third ring is called the Amalthea Gossamer Ring, named after moon Amalthea. The outer ring, the Thebe Gossamer Ring, is named after the moon Thebe. The outer edge of this ring is about 220,000 km (136,702 mi) from Jupiter.


The orbit of a planet is the time and path it takes to go around the Sun. In the amount of time it takes for Jupiter to orbit the Sun one time, the Earth orbits the Sun 11.86 times. One year on Jupiter is equal to 11.86 years on Earth. The average distance between Jupiter and the Sun is 778 million kilometres. This is five times the distance between Earth and the Sun. Jupiter is not tilted on its axis as much as the Earth or Mars. This causes it to have no seasons, for example Summer or Winter. Jupiter rotates, or spins around very quickly. This causes the planet to bulge in the middle. Jupiter is the fastest spinning planet in the Solar System. It completes one rotation or spin in 10 hours. Because of the bulge, the length of the equator of Jupiter is much longer than the length from pole to pole.

Research and exploration

From Earth

Jupiter is the third brightest object in the night sky, after the Moon and Venus. Because of that, people have always been able to see it from Earth. The first person known to really study the planet was Galileo Galilei in 1610. He was the first person to see Jupiter's moons Io, Europa, Ganymede and Callisto. This was because he used a telescope, unlike anyone before him.

No new moons were discovered for more than two hundred years. In 1892, astronomer E.E Barnard found a new moon using his observatory in California. He called the moon Amalthea. It was the last of Jupiter's 67 moons to be discovered by human observation through a telescope. In 1994, bits of the comet Shoemaker Levy-9 hit Jupiter. It was the first time a collision or crash between two Solar System objects had been directly seen by people.

From spacecraft

Seven spacecraft have flown past Jupiter since 1973. These were Pioneer 10 (1973), Pioneer 11 (1974), Voyagers 1 and 2 (1979), Ulysses (1992 and 2004), Cassini (2000) and New Horizons (2007).

The Pioneer missions were the first spacecraft to take close up pictures of Jupiter and its moons. Five years later, the two Voyager spacecraft discovered over 20 new moons. They captured photo evidence of lightning on the night side of Jupiter.

The Ulysses probe was sent to study the Sun. It only went to Jupiter after it had finished its main mission. Ulysses had no cameras so it took no photographs. In 2006, the Cassini spacecraft, on its way to Saturn, took some very good, very clear pictures of the planet. Cassini also found a moon and took a picture of it but it was too far away to show the details.

The Galileo mission in 1995 was the first spacecraft to go into orbit around Jupiter. It flew around the planet for seven years and studied all of the four biggest moons. It launched a probe into the planet to get information about Jupiter's atmosphere. The probe travelled to a depth of about 150 km before it was crushed by the weight of all the gas above it. This is called pressure. The Galileo spacecraft was also crushed in 2003 when NASA steered the craft into the planet on purpose. They did this so that the craft could not crash into Europa, a moon which scientists think might have life.

NASA have sent another spacecraft to Jupiter called Juno. It was launched on August 5, 2011. The spacecraft arrived at Jupiter on July 4, 2016. Several missions have been planned to send spacecraft to Jupiter's moons Europa and Callisto. One called JIMO (Jupiter Icy Moons Orbiter) was cancelled in 2006 because it cost too much money.


Jupiter has 67 known moons. The four largest were seen by Galileo with his primitive telescope, and nine more can be seen from Earth with modern telescopes. The rest of the moons have been identified by spacecraft. The smallest moon (S/2003 J 12) is only one kilometre across. The largest, Ganymede, has a diameter of 5,262 kilometres. It is bigger than the planet Mercury. The other three Galilean moons are Io, Europa and Callisto. Because of the way they orbit Jupiter, gravity affects three of these moons greatly. The friction caused by the gravity of Europa and Ganymede pulling on Io makes it the most volcanic object in the Solar System. It has over 400 volcanoes, more than three times as many as Earth.

Jupiter in the Solar System

A diagram of the inner Solar System. It shows the two groups of Trojan asteroids that follow Jupiter in its orbit

Jupiter's large gravity has had a big effect on the Solar System. Jupiter protects the inner planets from comets by pulling them towards itself. Because of this, Jupiter has the most comet impacts in the Solar System.

Two groups of asteroids, called Trojan asteroids, have settled into Jupiter's orbit round the Sun. One group is called the Trojans and the other group is called the Greeks. They go around the Sun at the same time as Jupiter.

Related pages


Jupiter for Kids. Kiddle Encyclopedia.