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Designations | |||||||||||||
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Pronunciation | /ˈdʒuːpɪtər/ ⓘ[1] | ||||||||||||
Named after | Jupiter | ||||||||||||
Adjectives | Jovian /ˈdʒoʊviən/ | ||||||||||||
Symbol | |||||||||||||
Orbital characteristics[2] | |||||||||||||
Epoch J2000 | |||||||||||||
Aphelion | 5.4570 AU (816.363 million km) | ||||||||||||
Perihelion | 4.9506 AU (740.595 million km) | ||||||||||||
5.2038 AU (778.479 million km) | |||||||||||||
Eccentricity | 0.0489 | ||||||||||||
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398.88 d | |||||||||||||
Average orbital speed | 13.07 km/s (8.12 mi/s) | ||||||||||||
20.020°[4] | |||||||||||||
Inclination | |||||||||||||
100.464° | |||||||||||||
21 January 2023[6] | |||||||||||||
273.867°[4] | |||||||||||||
Known satellites | 95 (as of 2023[update])[7] | ||||||||||||
Physical characteristics[2][8][9] | |||||||||||||
Mean radius | 69,911 km (43,441 mi)[a] 10.973 of Earth's | ||||||||||||
Equatorial radius | 71,492 km (44,423 mi)[a] 11.209 R🜨 (of Earth's) 0.10045 R☉ (of Sun's) | ||||||||||||
Polar radius | 66,854 km (41,541 mi)[a] 10.517 of Earth's | ||||||||||||
Flattening | 0.06487 | ||||||||||||
6.1469×1010 km2 (2.3733×1010 sq mi) 120.4 of Earth's | |||||||||||||
Volume | 1.4313×1015 km3 (3.434×1014 cu mi)[a] 1,321 of Earth's | ||||||||||||
Mass | 1.8982×1027 kg (4.1848×1027 lb)
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Mean density | 1.326 g/cm3 (0.0479 lb/cu in)[b] | ||||||||||||
Equatorial surface gravity | 24.79 m/s2 (81.3 ft/s2)[a] 2.528 g | ||||||||||||
0.2756±0.0006[11] | |||||||||||||
Equatorial escape velocity | 59.5 km/s (37.0 mi/s)[a] | ||||||||||||
9.9258 h (9 h 55 m 33 s)[3] | |||||||||||||
9.9250 hours (9 h 55 m 30 s) | |||||||||||||
Equatorial rotation velocity | 12.6 km/s (7.8 mi/s; 45,000 km/h) | ||||||||||||
3.13° (to orbit) | |||||||||||||
North pole right ascension | 268.057°; 17h 52m 14s | ||||||||||||
North pole declination | 64.495° | ||||||||||||
0.503 (Bond)[12] 0.538 (geometric)[13] | |||||||||||||
Temperature | 88 K (−185 °C) (blackbody temperature) | ||||||||||||
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−2.94[14] to −1.66[14] | |||||||||||||
−9.4[15] | |||||||||||||
29.8" to 50.1" | |||||||||||||
Atmosphere[2] | |||||||||||||
Surface pressure | 200–600 kPa (30–90 psi) (opaque cloud deck)[16] | ||||||||||||
27 km (17 mi) | |||||||||||||
Composition by volume | |||||||||||||
Since 1973, Jupiter has been visited by nine robotic probes: seven flybys and two dedicated orbiters, with one more en route and one awaiting launch. Jupiter is surrounded by a faint planetary ring system and has a powerful magnetosphere, the second largest contiguous structure in the Solar System (after the heliosphere). Jupiter forms a system of 95 known moons and probably many more, including the four large moons discovered by Galileo Galilei in 1610: Io, Europa, Ganymede, and Callisto. Ganymede, the largest of the four, is larger than the planet Mercury. Callisto is the second largest; Io and Europa are approximately the size of Earth's Moon. Jupiter was the first planet to form, and its inward migration during the primordial Solar System impacted much of the formation history of the other planets. Hydrogen constitutes 90% of Jupiter's volume, followed by helium, which forms 25% of its mass and 10% of its volume. The ongoing contraction of Jupiter's interior generates more heat than the planet receives from the Sun. Its internal structure is believed to consist of an outer mantle of fluid metallic hydrogen and a diffuse inner core of denser material. Because of its rapid rotation rate of one rotation per ten hours, Jupiter's shape is an oblate spheroid; it possesses a slight but noticeable bulge around the equator. The outer atmosphere is divided into a series of latitudinal bands, with turbulence and storms along their interacting boundaries. The most obvious result of this is the Great Red Spot, a giant storm that has been recorded since at least 1831. Jupiter is the fifth planet from the Sun and the largest in the Solar System. A gas giant, Jupiter's mass is more than two and a half times that of all the other planets in the Solar System combined and slightly less than one one-thousandth the mass of the Sun. Jupiter orbits the Sun at a distance of 5.20 AU (778.5 Gm) with an orbital period of 11.86 years. It is the third brightest natural object in the Earth's night sky after the Moon and Venus and has been observed since prehistoric times. Its name derives from Jupiter, the chief deity of ancient Roman religion.
Observation of Jupiter dates back to at least the Babylonian astronomers of the 7th or 8th century BC. The ancient Chinese knew Jupiter as the "Suì Star" (Suìxīng 歲星) and established their cycle of 12 earthly branches based on the approximate number of years it takes Jupiter to rotate around the Sun; the Chinese language still uses its name (simplified as 歲) when referring to years of age. By the 4th century BC, these observations had developed into the Chinese zodiac, and each year became associated with a Tai Sui star and god controlling the region of the heavens opposite Jupiter's position in the night sky. These beliefs survive in some Taoist religious practices and in the East Asian zodiac's twelve animals. The Chinese historian Xi Zezong has claimed that Gan De, an ancient Chinese astronomer, reported a small star "in alliance" with the planet, which may indicate a sighting of one of Jupiter's moons with the unaided eye. If true, this would predate Galileo's discovery by nearly two millennia. A 2016 paper reports that trapezoidal rule was used by Babylonians before 50 BC for integrating the velocity of Jupiter along the ecliptic. In his 2nd century work the Almagest, the Hellenistic astronomer Claudius Ptolemaeus constructed a geocentric planetary model based on deferents and epicycles to explain Jupiter's motion relative to Earth, giving its orbital period around Earth as 4332.38 days, or 11.86 years. In 1610, Italian polymath Galileo Galilei discovered the four largest moons of Jupiter (now known as the Galilean moons) using a telescope. This is thought to be the first telescopic observation of moons other than Earth's. Just one day after Galileo, Simon Marius independently discovered moons around Jupiter, though he did not publish his discovery in a book until 1614. It was Marius's names for the major moons, however, that stuck: Io, Europa, Ganymede, and Callisto. The discovery was a major point in favour of Copernicus' heliocentric theory of the motions of the planets; Galileo's outspoken support of the Copernican theory led to him being tried and condemned by the Inquisition. In the autumn of 1639, the Neapolitan optician Francesco Fontana tested a 22-palm telescope of his own making and discovered the characteristic bands of the planet's atmosphere. During the 1660s, Giovanni Cassini used a new telescope to discover spots in Jupiter's atmosphere, observe that the planet appeared oblate, and estimate its rotation period. In 1692, Cassini noticed that the atmosphere undergoes a differential rotation. The Great Red Spot may have been observed as early as 1664 by Robert Hooke and in 1665 by Cassini, although this is disputed. The pharmacist Heinrich Schwabe produced the earliest known drawing to show details of the Great Red Spot in 1831. The Red Spot was reportedly lost from sight on several occasions between 1665 and 1708 before becoming quite conspicuous in 1878. It was recorded as fading again in 1883 and at the start of the 20th century. Both Giovanni Borelli and Cassini made careful tables of the motions of Jupiter's moons, which allowed predictions of when the moons would pass before or behind the planet. By the 1670s, Cassini observed that when Jupiter was on the opposite side of the Sun from Earth, these events would occur about 17 minutes later than expected. Ole Rømer deduced that light does not travel instantaneously (a conclusion that Cassini had earlier rejected), and this timing discrepancy was used to estimate the speed of light. In 1892, E. E. Barnard observed a fifth satellite of Jupiter with the 36-inch (910 mm) refractor at Lick Observatory in California. This moon was later named Amalthea. It was the last planetary moon to be discovered directly by a visual observer through a telescope. An additional eight satellites were discovered before the flyby of the Voyager 1 probe in 1979.[e] In 1932, Rupert Wildt identified absorption bands of ammonia and methane in the spectra of Jupiter. Three long-lived anticyclonic features called "white ovals" were observed in 1938. For several decades, they remained as separate features in the atmosphere, sometimes approaching each other but never merging. Finally, two of the ovals merged in 1998, then absorbed the third in 2000, becoming Oval BA. In 1955, Bernard Burke and Kenneth Franklin discovered that Jupiter emits bursts of radio waves at a frequency of 22.2 MHz.: 36 The period of these bursts matched the rotation of the planet, and they used this information to determine a more precise value for Jupiter's rotation rate. Radio bursts from Jupiter were found to come in two forms: long bursts (or L-bursts) lasting up to several seconds, and short bursts (or S-bursts) lasting less than a hundredth of a second. Scientists have discovered three forms of radio signals transmitted from Jupiter: Jupiter has been visited by automated spacecraft since 1973, when the space probe Pioneer 10 passed close enough to Jupiter to send back revelations about its properties and phenomena. Missions to Jupiter are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Entering a Hohmann transfer orbit from Earth to Jupiter from low Earth orbit requires a delta-v of 6.3 km/s, which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit. Gravity assists through planetary flybys can be used to reduce the energy required to reach Jupiter. Beginning in 1973, several spacecraft performed planetary flyby manoeuvres that brought them within the observation range of Jupiter. The Pioneer missions obtained the first close-up images of Jupiter's atmosphere and several of its moons. They discovered that the radiation fields near the planet were much stronger than expected, but both spacecraft managed to survive in that environment. The trajectories of these spacecraft were used to refine the mass estimates of the Jovian system. Radio occultations by the planet resulted in better measurements of Jupiter's diameter and the amount of polar flattening.: 47 Six years later, the Voyager missions vastly improved the understanding of the Galilean moons and discovered Jupiter's rings. They also confirmed that the Great Red Spot was anticyclonic. Comparison of images showed that the Spot had changed hues since the Pioneer missions, turning from orange to dark brown. A torus of ionized atoms was discovered along Io's orbital path, which were found to come from erupting volcanoes on the moon's surface. As the spacecraft passed behind the planet, it observed flashes of lightning in the night side atmosphere.: 87 The next mission to encounter Jupiter was the Ulysses solar probe. In February 1992, it performed a flyby manoeuvre to attain a polar orbit around the Sun. During this pass, the spacecraft studied Jupiter's magnetosphere, although it had no cameras to photograph the planet. The spacecraft passed by Jupiter six years later, this time at a much greater distance. In 2000, the Cassini probe flew by Jupiter on its way to Saturn, and provided higher-resolution images. The New Horizons probe flew by Jupiter in 2007 for a gravity assist en route to Pluto. The probe's cameras measured plasma output from volcanoes on Io and studied all four Galilean moons in detail. The first spacecraft to orbit Jupiter was the Galileo mission, which reached the planet on December 7, 1995. It remained in orbit for over seven years, conducting multiple flybys of all the Galilean moons and Amalthea. The spacecraft also witnessed the impact of Comet Shoemaker–Levy 9 when it collided with Jupiter in 1994. Some of the goals for the mission were thwarted due to a malfunction in Galileo's high-gain antenna. A 340-kilogram titanium atmospheric probe was released from the spacecraft in July 1995, entering Jupiter's atmosphere on December 7. It parachuted through 150 km (93 mi) of the atmosphere at a speed of about 2,575 km/h (1,600 mph) and collected data for 57.6 minutes until the spacecraft was destroyed. The Galileo orbiter itself experienced a more rapid version of the same fate when it was deliberately steered into the planet on September 21, 2003. NASA destroyed the spacecraft to avoid any possibility of the spacecraft crashing into and possibly contaminating the moon Europa, which may harbour life. Data from this mission revealed that hydrogen composes up to 90% of Jupiter's atmosphere. The recorded temperature was more than 300 °C (570 °F), and the wind speed measured more than 644 km/h (>400 mph) before the probes vaporized. NASA's Juno mission arrived at Jupiter on July 4, 2016, with the goal of studying the planet in detail from a polar orbit. The spacecraft was originally intended to orbit Jupiter thirty-seven times over a period of twenty months. During the mission, the spacecraft will be exposed to high levels of radiation from Jupiter's magnetosphere, which may cause the failure of certain instruments. On August 27, 2016, the spacecraft completed its first flyby of Jupiter and sent back the first-ever images of Jupiter's north pole. Juno completed 12 orbits before the end of its budgeted mission plan, ending in July 2018. In June of that year, NASA extended the mission operations plan to July 2021, and in January of that year the mission was extended to September 2025 with four lunar flybys: one of Ganymede, one of Europa, and two of Io. When Juno reaches the end of the mission, it will perform a controlled deorbit and disintegrate into Jupiter's atmosphere. This will avoid the risk of collision with Jupiter's moons. There is great interest in missions to study Jupiter's larger icy moons, which may have subsurface liquid oceans. Funding difficulties have delayed progress, causing NASA's JIMO (Jupiter Icy Moons Orbiter) to be cancelled in 2005. A subsequent proposal was developed for a joint NASA/ESA mission called EJSM/Laplace, with a provisional launch date around 2020. EJSM/Laplace would have consisted of the NASA-led Jupiter Europa Orbiter and the ESA-led Jupiter Ganymede Orbiter. However, the ESA formally ended the partnership in April 2011, citing budget issues at NASA and the consequences on the mission timetable. Instead, ESA planned to go ahead with a European-only mission to compete in its L1 Cosmic Vision selection. These plans have been realized as the European Space Agency's Jupiter Icy Moon Explorer (JUICE), launched on April 14, 2023, followed by NASA's Europa Clipper mission, scheduled for launch in 2024. Other proposed missions include the Chinese National Space Administration's Tianwen-4 mission which aims to launch an orbiter to the Jovian system and possibly Callisto around 2035, and CNSA's Interstellar Express and NASA's Interstellar Probe, which would both use Jupiter's gravity to help them reach the edges of the heliosphere.