Jupiter: The Giant Planet and the Bringer of Luck

What is Jupiter?

Jupiter is the largest planet: a gas giant about 143,000 km across, 11 times Earth’s width, with more than twice the mass of all the other planets together. It is made mostly of hydrogen and helium, with no solid surface, and its bands of cloud are crossed by storms such as the Great Red Spot, wider than Earth. It orbits the Sun at an average of 778.5 million km (5.2 au) and goes around in 11.9 years. Dozens of moons circle it, the four largest visible in small binoculars.

Where Jupiter is in the sky

The ecliptic is the path the Sun appears to follow across our sky over a year, the plane of Earth’s orbit seen from Earth. Positions along it are measured in degrees, from 0° at the March equinox to 360°. The zodiac divides it into twelve equal 30° parts named after signs: Aries covers 0° to 30°, Taurus 30° to 60°, and so on. The signs are counted from the equinox, not from the star patterns they were named after; those constellations now sit about 24° further along, because Earth’s axis slowly wobbles (precession).

Jupiter moves along the ecliptic at up to about 0.25° a day and spends about a year in each sign, going around the zodiac in 12 years.

Jupiter in astrology

In astrology Jupiter stands for growth, luck, optimism, wisdom and opportunity. It rules Sagittarius, and in traditional astrology also Pisces. Because it spends about a year in a sign, astrology reads its sign as the year’s area of expansion for each sign, shown below.