Solar system · Jupiter

Where is Jupiter right now?

Jupiter and its cloud bands, drawn from its maps in Exo-View

Jupiter is the largest planet by far, more than twice as massive as all the others put together, and it takes nearly 12 years to go once round the Sun, so it spends about a year in each constellation of the zodiac. Exo-View puts it where it is at this moment, with its four big moons beside it.

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Orbit: 11.86 years
Distance from the Sun: 5.2 AU on average, about 778 million km
Width: About 140,000 km: eleven Earths side by side
Mass: 318 times the Earth's, about 2.5 times all the other planets together
Day: 9 hours 55 minutes, the shortest of any planet
Moons: More than ninety known; the four big ones are Io, Europa, Ganymede and Callisto
Brightness: After the Moon and Venus, usually the brightest thing in the night sky

Why it moves so slowly

Jupiter's year is nearly 12 Earth years, so it creeps round the sky. Earth overtakes it about every 13 months, and at that moment, its opposition, Jupiter is nearest, brightest and up all night. A few months either side it is still easy to see; about half a year after opposition it is behind the Sun, and for a few weeks it cannot be seen at all.

The four big moons

Galileo turned a telescope on Jupiter in January 1610 and saw four small stars in a line beside it that changed places from night to night. They were moons going round it, the first seen to circle a planet other than the Earth. Ganymede is the biggest moon in the solar system, larger than Mercury; Io is the most volcanic body known; Europa hides an ocean under its ice; Callisto is the most heavily cratered. Good binoculars, held steady, show all four.

What it is

Jupiter has no surface to stand on: it is mostly hydrogen and helium, thickening with depth to a liquid and perhaps a small core. Its bands are winds blowing in opposite directions at hundreds of km/h, and the Great Red Spot, a storm wider than the Earth, has been watched for more than 150 years. It has faint rings and a magnetic field the strongest of any planet.

In Exo-View

The key below flies out to Jupiter, mapped from its photographs. Its four big moons are placed where they are now, so you can see which side of the planet Io is on today, and open each one's plate from there.