50 Fun Facts About Jupiter

Where does Jupiter rank in distance from the Sun?

Jupiter is the fifth planet from the Sun, the first of the giant planets beyond the asteroid belt, after Mercury, Venus, Earth and Mars.

Jupiter's mass is roughly how many times that of Earth?

Jupiter's mass is about 318 times Earth's, nearly 2.5 times that of all the other planets combined, yet under a thousandth of the Sun's.

Jupiter's diameter is about how many times Earth's?

Jupiter's equatorial diameter of about 143,000 km is roughly 11 times Earth's 12,742 km and about a tenth of the Sun's.

How long does Jupiter take to orbit the Sun?

Jupiter takes about 11.9 years to orbit the Sun; Chinese astronomers called it the Year Star and tied the twelve earthly branches to its near-12-year cycle.

Roughly how long is a day on Jupiter?

A Jovian day lasts about 10 hours (9 h 56 m), the fastest spin of any planet; the rotation flattens Jupiter into an oblate spheroid about 7% wider at the equator.

Jupiter's atmosphere is made mostly of which two gases?

About 76% hydrogen and 24% helium by mass, close to the primordial mix of the solar nebula.

What is the Great Red Spot?

The Great Red Spot is a giant anticyclonic storm, spinning counterclockwise about once every six Earth days and rising some 8 km above the surrounding cloud tops.

Since when has the Great Red Spot been continuously observed?

The Great Red Spot has been observed continuously since 1831; earlier sightings by Robert Hooke (1664) and Cassini (1665) are disputed and may have been a different storm.

In which part of Jupiter does the Great Red Spot sit?

The Great Red Spot sits in Jupiter's southern hemisphere at about 22 degrees south latitude, pinned between the South Equatorial Belt and the South Tropical Zone.

Roughly how wide was the Great Red Spot in the late 1800s, before it began shrinking?

In the late 1800s the Great Red Spot spanned about 41,000 km, over three Earth diameters; by 2015 it had shrunk to roughly 16,500 by 10,940 km.

Jupiter's clouds are made mainly of crystals of what?

Jupiter's visible clouds are mostly ammonia crystals, with ammonium hydrosulfide below; the orange and brown streaks come from compounds welling up and changing colour in sunlight.

Which mechanism makes Jupiter radiate more heat than it receives from the Sun?

Kelvin–Helmholtz contraction drives it: Jupiter slowly contracts under its own gravity, converting gravitational energy into heat, so its interior heat outstrips what it absorbs from the Sun.

Jupiter's magnetotail stretches out roughly as far as the orbit of which planet?

Jupiter's magnetotail, the downwind side of the strongest planetary magnetosphere in the Solar System, stretches almost to the orbit of Saturn, hundreds of millions of kilometres away.

What exotic material is thought to make up Jupiter's outer mantle and generate its magnetic field?

Fluid metallic hydrogen, formed when pressure strips hydrogen's electrons so it conducts like a liquid metal, makes up much of Jupiter's interior and drives its dynamo.

Jupiter is the only planet whose barycentre with the Sun lies where?

Jupiter's barycentre with the Sun lies outside the Sun's surface, about 7% of a solar radius above it, because Jupiter holds over twice the mass of all the other planets combined.

Where does Jupiter usually rank among the brightest natural objects in the night sky?

Jupiter is usually the third-brightest natural object in the night sky, after the Moon and Venus; only at a favourable opposition can Mars briefly outshine it.

Which Galilean moon orbits farthest from Jupiter?

Callisto is the outermost Galilean moon, orbiting about 1.88 million km from Jupiter, far enough to escape the tidal heating that shapes the inner three; its ancient surface is saturated with craters.

Which four moons were discovered by telescope in 1610?

Io, Europa, Ganymede and Callisto were first seen in January 1610 through an early telescope, the first moons known to orbit a planet other than Earth; they are the Galilean moons.

Who gave the four big moons the names that stuck, taken from Zeus's lovers?

Simon Marius published the names that stuck, drawn from Zeus's lovers, in his 1614 Mundus Iovialis; their discoverer had called them the Medicean Stars after his patrons.

Which moon of Jupiter is the largest moon in the Solar System, bigger than the planet Mercury?

Ganymede, 5,268 km across, is the largest moon in the Solar System, outsizing Mercury, and the only moon known to generate its own magnetic field.

Which moon of Jupiter is the most volcanically active body in the Solar System?

Io, with over 400 active volcanoes, is the most volcanically active body in the Solar System; tidal flexing by Jupiter and the neighbouring Galilean moons heats its interior.

Which icy moon of Jupiter is a prime target in the search for life because of its subsurface ocean?

Europa hides a salty ocean beneath its icy shell, with Hubble detecting possible water-vapour plumes in the 2010s; NASA launched the Europa Clipper mission in October 2024 to study it.

The three inner Galilean moons orbit in a 4:2:1 pattern known as what?

The 4:2:1 pattern is a Laplace resonance: each moon receives a gravitational tug at the same point every orbit, keeping their orbits slightly elliptical and their interiors tidally warmed.

Which moon, found by Barnard in 1892, was the last discovered by eye through a telescope?

Amalthea, spotted by E. E. Barnard at Lick Observatory in 1892, was the last moon in the Solar System discovered by direct visual observation; everything since has come from photographs or spacecraft.

What are Jupiter's faint rings mostly made of?

Jupiter's rings are mostly fine dust, unlike Saturn's icy rings; the main ring is thought to be debris knocked off the small moons Adrastea and Metis by meteoroid impacts.

Which spacecraft discovered Jupiter's rings, in 1979?

Voyager 1 discovered Jupiter's faint ring system in March 1979, photographing it in a long exposure as the probe looked back toward the Sun; Voyager 2 confirmed it that July.

Which was the first spacecraft to fly past Jupiter, in 1973?

Pioneer 10 made the first flyby of Jupiter on 3 December 1973, having already been the first probe to cross the asteroid belt; its signal was last detected in 2003.

Which was the first spacecraft to orbit Jupiter, arriving in December 1995?

Galileo entered orbit on 7 December 1995 and circled Jupiter for nearly eight years, dropping a probe into the atmosphere despite its jammed high-gain antenna; it was deorbited in September 2003.

For roughly how long did the 1995 atmospheric entry probe transmit from inside Jupiter's atmosphere?

The 1995 entry probe parachuted into Jupiter's atmosphere on 7 December and transmitted for about an hour (58 minutes), descending some 150 km before pressure and heat destroyed it.

NASA's Juno spacecraft arrived at Jupiter on which US holiday in 2016?

Juno entered orbit on 4 July 2016, Independence Day, after a five-year journey; it returned the first close-up images of Jupiter's poles and found clusters of polar cyclones.

Juno found a group of how many cyclones around Jupiter's north pole?

A central storm ringed by eight others; the south pole has a similar arrangement.

Which comet, torn into fragments, crashed into Jupiter in July 1994?

Comet Shoemaker–Levy 9 struck Jupiter in more than 20 fragments between 16 and 22 July 1994, the first collision between Solar System bodies ever observed directly.

Why had the 1994 impactor comet broken into a chain of pieces before it hit the planet?

Tidal forces tore the comet apart when it passed inside Jupiter's Roche limit in July 1992; it had been captured into orbit around the planet decades before its 1993 discovery.

Jupiter has been called the Solar System's what, because of how many impacts it absorbs?

Jupiter has been called the Solar System's vacuum cleaner: its gravity draws in far more asteroid and comet impacts than Earth receives, though whether it shields the inner planets is debated.

Asteroids sharing Jupiter's orbit at its Lagrange points are known as what?

Jupiter's Trojans share its orbit at the L4 and L5 Lagrange points, split into Greek and Trojan 'camps' named for heroes of the Iliad; the first found, in 1906, was 588 Achilles.

Timing the eclipses of Jupiter's moons in the 1670s allowed Ole Rømer to estimate what?

Ole Rømer estimated the speed of light in 1676 after noticing that eclipses of Jupiter's innermost big moon ran late when Earth was farthest away, about 22 minutes across Earth's orbit.

Which Babylonian god did the planet Jupiter represent?

Babylonian astronomers identified the planet with Marduk, their chief god; they used its roughly 12-year circuit along the ecliptic to define the constellations of their zodiac.

Chinese, Japanese, Korean and Vietnamese names for Jupiter mean which of the Five Elements' 'star'?

Jupiter is the Wood Star (Chinese Mùxīng, Japanese Mokusei) in the Five Elements scheme; it was also called the Year Star because it moves one zodiac sign a year.

Hindu astrologers named the planet after Brihaspati and call it Guru, meaning what?

Brihaspati is the religious teacher of the gods in Vedic tradition.

The old adjective 'jovial', from Jupiter's astrological influence, has come to mean what?

Jovial, from Jupiter's supposed astrological influence on those born under it, means merry or good-humoured; astronomers use 'Jovian' for the planet itself.

The name Jupiter comes from a Proto-Indo-European compound meaning what?

Jupiter comes from Proto-Indo-European *Dyēu-pəter, 'Father Sky-God' or sky father, the same compound behind Greek Zeu pater and Sanskrit Dyaus Pita.

What is the identifying weapon of the Roman god Jupiter?

Jupiter's weapon is the thunderbolt, often shown clutched in the talons of his sacred eagle, the bird that became the standard of the Roman legions.

The ancient Greeks knew the planet as Phaethon, meaning what?

Phaethon means 'shining one' or 'blazing'; the ancient Greeks applied it to the planet before naming it for Zeus, and its modern Greek name Dias derives from Zeus's genitive Dios.

Oval BA, nicknamed Red Spot Junior, formed in 2000 from how many merging white ovals?

Oval BA, nicknamed Red Spot Junior, formed in 2000 when three white ovals that had existed since 1939–40 finished merging; it turned red in 2005–06.

Which spacecraft used a Jupiter gravity assist in 2007 on its way to Pluto?

New Horizons swung past Jupiter on 28 February 2007, a gravity assist that cut about three years from its journey to Pluto; it photographed the Little Red Spot on the way.

Jupiter's orbital period is roughly what fraction of Saturn's, forming a near-resonance?

Jupiter's 11.86-year orbit is about two-fifths of Saturn's 29.46 years, a near 5:2 commensurability that astronomers call the Great Inequality, which produces a slow, roughly 900-year wobble in both orbits.

A 'Great Cold Spot' was discovered in 2017 in which region of Jupiter?

The Great Cold Spot sits in Jupiter's upper atmosphere, the thermosphere near its north pole, a dark region about 24,000 km long spotted in 2017 through infrared emission from the trihydrogen cation (H3+).

By roughly how much does Jupiter shrink each year as it contracts under the Kelvin-Helmholtz mechanism?

Jupiter contracts by about 1 mm a year as it slowly cools, releasing gravitational energy as heat; when it formed it was hotter and roughly twice its present diameter.

Which pharmacist made the earliest known detailed drawing of the Great Red Spot, in 1831?

Heinrich Schwabe, a Dessau pharmacist turned astronomer better known for discovering the sunspot cycle, made the earliest known detailed drawing of the Great Red Spot, the start of its continuous record.

In 1955 Burke and Franklin found Jupiter emitting radio bursts at what frequency?

Bernard Burke and Kenneth Franklin detected Jupiter's decametric radio bursts at 22.2 MHz in 1955; their timing, locked to the planet's rotation, gave a precise spin period (System III).