♃ Jupiter

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STATISTICS

ORBITAL RADIUS

780 million km from the Sun (5 times the distance of the Earth from the Sun)

ORBITAL PERIOD

12 Earth years

DIAMETER

140,000 km (11 times the diameter of the Earth)

ROTATIONAL PERIOD

9.9 Earth hours

MASS

320 times the mass of the Earth

Moons

Jupiter is known to have (at least) 69 moons.

(Edit: literally two days after I wrote that, the figure jumped to 79 moons. This is why I used the term ‘at least’!)

The four largest are known as the Galilean moons, as they were discovered by Galileo, in 1610.

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Io is the closest to Jupiter, then Europa, Ganymede and finally Callisto.

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Ganymede is larger in diameter than Mercury, which also makes it larger than the Moon. Indeed, it is the largest moon in the solar system. Callisto and Io are also both larger than the Moon.

(The diameter of Io is 3,600 km, Europa is 3,100 km, Ganymede is 5,300 km and Callisto is 4,800 km. These compare with the diameter of the Moon, which is 3,500 km.)

In terms of mass, Ganymede is about double the mass of the Moon. Both Io and Callisto also have a greater mass than the Moon, but Europa has a smaller mass, despite being larger in volume.

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