♃ Jupiter

Named for the Roman god Jupiter (Greek: Zeus)

Sky Thunder King of the gods Oaths

Which sign is Jupiter in now?

Jupiter and Thetis by Jean-Auguste-Dominique Ingres
Jupiter and Thetis Jean-Auguste-Dominique Ingres, 1811 Musée Granet, Aix-en-Provence The painting shows the episode from Homer’s Iliad in which the sea nymph Thetis begs Jupiter to help her son Achilles. Jupiter sits on a throne in the clouds, with an eagle beside him. Public domain, via Wikimedia Commons

King of the gods, lord of the sky and thunder, and chief god of the Roman state.

The god

Jupiter was the god of the sky and thunder, the king of the gods, and the chief deity of the Roman state. His name comes from old Italic words for “sky” and “father,” so it means “sky father.” In the Capitoline Triad, with Juno and Minerva, he was the central guardian of the state, and his great temple on the Capitoline Hill was dedicated to Jupiter Optimus Maximus, “best and greatest”; victorious generals laid the tokens of their victory at the feet of his statue there. As the sky god he was the divine witness to oaths. His emblem was the thunderbolt, his sacred animal the eagle and his sacred tree the oak. The Romans saw him as the equal of the Greek Zeus.

How the planet got its name

NASA notes that the biggest planet takes its name from the king of the Roman gods. It is the third-brightest natural object in the night sky, after the Moon and Venus, and takes almost 12 years to circle the Sun. Babylonian astronomers associated it with Marduk, their chief god. Galileo and Simon Marius each spotted its four largest moons around January 1610, and Marius, on Johannes Kepler’s suggestion, named them Io, Europa, Ganymede and Callisto, for four lovers of Zeus.

Symbols

Eagle Thunderbolt Oak

The planet

A gas giant made, like the Sun, mostly of hydrogen and helium. Jupiter took most of the material left over after the Sun formed and ended up with more than twice the combined material of all the other bodies in the solar system. Its stripes are cold, windy clouds of ammonia and water, and the Great Red Spot is a storm bigger than Earth that has raged for hundreds of years. Its moon Io is the most volcanically active body in the solar system, and Europa may hide a vast ocean beneath its icy crust. Its rings were discovered by Voyager 1 in 1979.

Diameter
142,984 km 11 × Earth
Mass
1898 × 10²⁴ kg 318 × Earth
Gravity
23.1 m/s² 2.4 × Earth's
Length of day
9.9 hours sunrise to sunrise
Length of year
11.9 Earth years one trip around the Sun
Distance from the Sun
778.5 million km 5.2 AU (Earth = 1)
Average temperature
-110 °C -166 °F
Moons
95 NASA’s count
Rings
Yes

Figures from NASA’s Planetary Fact Sheet; the temperature is its “mean temperature.” Comparisons with Earth are worked out from the same sheet.

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