A guide to the planets: Jupiter

Jupiter is the largest planet in the Solar System and its upper atmosphere is ravaged by enormous storms

Jupiter is more massive than all of the other solar-system planets combined.

What is Jupiter like?

Jupiter is the undisputed King of the Planets. It’s a gas giant, its huge mass made up of hydrogen and helium.

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Its upper atmosphere is streaked by dark belts and white zones – streams of clouds that blow in alternating directions around the planet.

Caught between these are several huge storms. The largest of these, the Great Red Spot, has been raging for at least 150 years and could easily swallow the entire Earth.

Yet these features only make up the top few hundred km of Jupiter’s atmosphere.

It’s thought that some kind of solid core lies at Jupiter’s heart, as the density of the planet would be incredibly intense, but no one is sure exactly what this core would look like or what it’s made of.

Jupiter’s enormous mass and rapid spin mean that it balloons out at the equator, making the planet look like it’s been squashed at the poles; a shape known as an ‘oblate spheroid’.

The planet’s huge mass influences the entire Solar System, particularly the asteroid belt where the constant tug of the planet has created openings in the belt known as the Kirkwood gaps.

Animation of Jupiter's Great Red Spot
The Great Red Spot is an enormous storm that has been raging for centuries.
NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstadt/Justin Cowart

Jupiter Facts

  • Diameter: 142,984km at equator (11.2 times Earth), 133,708km through poles (10.5 times Earth)
  • Mass: 1898 trillion trillion kg (318 times Earth)
  • Distance from the Sun: 778.6 million km (5.27 AU)
  • Length of day: 9.9 hours
  • Length of year: 11.9 years
  • Number of moons: 79
  • Average temperature: -110ºC
  • No of spacecraft visitors: 6
  • Type of planet: Gas giant

How can I observe Jupiter?

Jupiter is best observed during opposition, when it makes its closest approach to Earth.

During this time the planet is clearly visible to the naked eye as the fourth brightest thing in the sky after the Sun, Moon and Venus.

Through binoculars or a small telescope you should be able to make out the Galilean moons – Jupiter’s four largest and closest moons – as well as features such as the Great Red Spot.

With high magnification you should see the planet’s bands come into view, provided the air of Earth’s atmosphere isn’t too turbulent.

From where does Jupiter get its name?

The planet is named after the king of the gods, Jupiter (Zeus in Greek) because of its impressive brightness.

Jupiter’s moons have had many different names and designations over the years but are now officially named after characters from Greek and Roman myths, most of whom were one of Jupiter’s many lovers.

How have we explored Jupiter?

Jupiter's north pole in the infrared.
NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM

Jupiter has been explored by six spacecraft but four of these were brief flyby missions.

The problem with observing Jupiter for any longer than a few hours is radiation.

The planet has an enormous and incredibly strong magnetic field, which traps charged particles creating belts of intense radiation that can cook electronics.

The two orbiters, Galileo and Juno, were built to resist the worst effects of radiation.

Juno is currently in orbit, attempting to look below the planet’s cloud layer using a combination of gravitational and magnetic measurements, as well as observing at wavelengths that the top layers of the atmosphere are transparent to, allowing the spacecraft to look below the cloud deck.

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Explored by: Pioneer 10 (1973, NASA); Pioneer 11 (1974, NASA); Voyager 1 (1979, NASA); Voyager 2 (1979, NASA); Galileo (1995, NASA); Juno (2016, NASA)