King of the planets
Jupiter
Jupiter is the fifth planet from the Sun and by far the largest: more than twice as massive as all the other planets combined. It is a gas giant made mostly of hydrogen and helium, with no solid surface to stand on.
Its striped clouds, the giant storm known as the Great Red Spot and its family of dozens of moons make Jupiter a miniature solar system of its own. It also spins faster than any other planet, completing a day in under ten hours.
Key facts
- Diameter
- 142,984 km11× Earth
- Mass
- 1.90 × 10²⁷ kg318× Earth
- Gravity
- 23.1 m/s²2.36 g
- Mean distance from Sun
- 5.20 AU≈ 778 million km
- Length of year
- 11.86 yrEarth days or years
- Length of day
- 9.9 hSunrise to sunrise
- Mean temperature
- -110°CAt the 1-bar level
- Known moons
- 95+As of 2025
- Axial tilt
- 3.1°
1 astronomical unit (AU) is Earth's average distance from the Sun, about 149.6 million km. Values follow the NASA Planetary Fact Sheet; many are averages and vary with how and where they are measured.
Physical characteristics
Jupiter is 142,984 km across at the equator — about 11 times Earth's diameter — and 318 times as massive as Earth. More than 1,300 Earths could fit inside it.
Its rapid rotation makes Jupiter visibly flattened, bulging at the equator. Its average density, 1,326 kg/m³, is only a little higher than water, reflecting its light, gaseous composition. Gravity at the cloud tops is about 2.4 times Earth's.
Atmosphere and climate
Jupiter's atmosphere is mostly hydrogen and helium. Clouds of ammonia, ammonium hydrosulfide and water form the bright 'zones' and darker 'belts' that wrap around the planet, separated by powerful jet streams. At the level where pressure equals Earth's sea-level pressure, the temperature is about −110°C.
The Great Red Spot is a high-pressure storm wider than Earth. It has been observed continuously since at least the 1830s and may be centuries older, though it has been shrinking over recent decades. Jupiter also has lightning and the most powerful aurorae of any planet.
Composition: H₂ 90% · He 10% · traces of CH₄, NH₃
Internal structure
No surface
Descending into Jupiter, the gas gets steadily denser and hotter until it behaves like a liquid. There is no point where you would land on solid ground.
Metallic hydrogen
Deep inside, enormous pressure turns hydrogen into an electrically conducting liquid called metallic hydrogen. Its motion generates a magnetic field that is between about 16 and 54 times stronger than Earth's at the cloud tops.
A fuzzy core
Gravity measurements from NASA's Juno spacecraft suggest Jupiter's core is not a compact ball of rock but a large, diluted region where heavy elements are mixed with hydrogen.
A giant magnetosphere
Jupiter's magnetic bubble is the largest planetary structure in the Solar System, and its radiation belts are intense enough to damage unprotected spacecraft electronics.
Moons and rings
Jupiter has at least 95 officially recognised moons. The four largest, discovered by Galileo Galilei in 1610, are worlds in their own right: Io is the most volcanically active body in the Solar System; Europa hides a global saltwater ocean beneath its icy crust; Ganymede is the largest moon in the Solar System, bigger than Mercury and the only moon with its own magnetic field; and Callisto is one of the most heavily cratered objects known.
Jupiter also has a faint system of rings made of dust, discovered by Voyager 1 in 1979.
Orbit and rotation
Jupiter orbits at an average of 5.2 AU (about 778 million km) and takes 11.86 Earth years to circle the Sun once.
It rotates in just 9.9 hours, the shortest day of any planet. With an axial tilt of only about 3°, Jupiter has almost no seasons.
Exploration and missions
Nine spacecraft have visited Jupiter, and two new missions are on their way to study its icy moons.
- 1973–1974
Pioneer 10 & 11 · NASA
The first spacecraft to fly past Jupiter and cross the asteroid belt.
- 1979
Voyager 1 & 2 · NASA
Discovered Jupiter's rings and active volcanoes on Io.
- 1995–2003
Galileo · NASA
The first Jupiter orbiter; it dropped a probe into the atmosphere and found evidence of Europa's ocean.
- 2016–
Juno · NASA
Studies Jupiter's interior, gravity, magnetic field and poles from a polar orbit.
- 2023–
JUICE · ESA
Launched in 2023 to study Ganymede, Callisto and Europa; it is due to reach Jupiter in 2031.
- 2024–
Europa Clipper · NASA
Launched in 2024 to investigate whether Europa could support life; arrival is planned for 2030.
Surprising facts about Jupiter
- Jupiter is so massive that the centre of mass it shares with the Sun lies just outside the Sun's surface.
- Its moon Ganymede is larger than the planet Mercury.
- A day on Jupiter lasts less than ten hours.
- Jupiter gives off more heat than it receives from the Sun, left over from its formation.
- In 1994 fragments of comet Shoemaker–Levy 9 slammed into Jupiter, leaving dark scars larger than Earth.
Jupiter compared with Earth
| Property | Jupiter | Earth |
|---|---|---|
| Diameter | 142,984 km | 12,756 km |
| Mass (Earth = 1) | 317.9 | 1.000 |
| Gravity | 2.36 g | 1.00 g |
| Day | 9.9 h | 24.0 h |
| Year | 11.86 yr | 365.2 d |
| Mean temperature | -110°C | 15°C |
| Moons | 95 | 1 |
Keep exploring
- Saturn: the ringed giant
- Mars: the red planet
- Uranus: the sideways ice giant
- Europa Clipper — searching for a habitable ocean
- JUICE — europe's explorer of jupiter's icy moons
- Juno — peering beneath jupiter's clouds
- Lucy — a tour of jupiter's trojan asteroids
- New Horizons — the first mission to pluto
- Pioneer 10 — the first visitor to jupiter
- Voyager 1 — the most distant human-made object
- Voyager 2 — the only visitor to uranus and neptune
- Fly to Jupiter in the interactive 3D solar system
- All eight planets of the Solar System