215-678: Jupiter is the fifth planet from the Sun and the largest in the Solar System . It is a gas giant with a mass more than 2.5 times that of all the other planets in the Solar System combined and slightly less than one-thousandth the mass of the Sun. Its diameter is eleven times that of Earth , and a tenth that 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
430-669: 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
645-469: A geodynamo that generates a magnetic field . Similar differentiation processes are believed to have occurred on some of the large moons and dwarf planets, though the process may not always have been completed: Ceres, Callisto, and Titan appear to be incompletely differentiated. The asteroid Vesta, though not a dwarf planet because it was battered by impacts out of roundness, has a differentiated interior similar to that of Venus, Earth, and Mars. All of
860-460: A nebula to create a young protostar orbited by a protoplanetary disk . Planets grow in this disk by the gradual accumulation of material driven by gravity , a process called accretion . The word planet comes from the Greek πλανήται ( planḗtai ) ' wanderers ' . In antiquity , this word referred to the Sun , Moon , and five points of light visible to the naked eye that moved across
1075-406: A rogue planet , is believed to be orbited by a tiny protoplanetary disc , and the sub-brown dwarf OTS 44 was shown to be surrounded by a substantial protoplanetary disk of at least 10 Earth masses. The idea of planets has evolved over the history of astronomy, from the divine lights of antiquity to the earthly objects of the scientific age. The concept has expanded to include worlds not only in
1290-464: A system of multiple protostars , which are quite common, with Jupiter being the second but failed protostar. But the Solar System never developed into a system of multiple stars and Jupiter does not qualify as a protostar or brown dwarf since it does not have enough mass to fuse hydrogen. According to the " grand tack hypothesis ", Jupiter began to form at a distance of roughly 3.5 AU (520 million km ; 330 million mi ) from
1505-519: A triaxial ellipsoid . The exoplanet Tau Boötis b and its parent star Tau Boötis appear to be mutually tidally locked. The defining dynamic characteristic of a planet, according to the IAU definition, is that it has cleared its neighborhood . A planet that has cleared its neighborhood has accumulated enough mass to gather up or sweep away all the planetesimals in its orbit. In effect, it orbits its star in isolation, as opposed to sharing its orbit with
1720-555: A 1:2 resonance, which caused Saturn to shift into a higher orbit, disrupting the orbits of Uranus and Neptune, depleting the Kuiper belt, and triggering the Late Heavy Bombardment . Based on Jupiter's composition, researchers have made the case for an initial formation outside the molecular nitrogen (N 2 ) snow line, which is estimated at 20–30 AU (3.0–4.5 billion km; 1.9–2.8 billion mi) from
1935-480: 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
2150-436: A 3:2 mean motion resonance at approximately 1.5 AU (220 million km; 140 million mi) from the Sun. This changed the direction of migration, causing them to migrate away from the Sun and out of the inner system to their current locations. All of this happened over a period of 3–6 million years, with the final migration of Jupiter occurring over several hundred thousand years. Jupiter's migration from
2365-461: A Greek zeta with a horizontal stroke , ⟨Ƶ⟩ , as an abbreviation for Zeus . In Latin, Iovis is the genitive case of Iuppiter , i.e. Jupiter. It is associated with the etymology of Zeus ('sky father'). The English equivalent, Jove , is known to have come into use as a poetic name for the planet around the 14th century. Jovian is the adjectival form of Jupiter. The older adjectival form jovial , employed by astrologers in
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#17327658030902580-608: 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 the heliocentric theory of the motions of the planets by Nicolaus Copernicus ; 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
2795-504: A boundary, even though deuterium burning does not last very long and most brown dwarfs have long since finished burning their deuterium. This is not universally agreed upon: the exoplanets Encyclopaedia includes objects up to 60 M J , and the Exoplanet Data Explorer up to 24 M J . The smallest known exoplanet with an accurately known mass is PSR B1257+12A , one of the first exoplanets discovered, which
3010-494: A bride, and names it Daidale. When preparations are being made for the wedding, Hera rushes down from Cithaeron, followed by the women of Plataia , and upon discovering the trick, the couple are reconciled, with the matter ending in joy and laughter among all involved. After his marriage to Hera, different authors describe Zeus's numerous affairs with various mortal women. In many of these affairs, Zeus transforms himself into an animal, someone else, or some other form. According to
3225-466: A combined mass 7–25 times the Earth. This mixing process could have arisen during formation, while the planet accreted solids and gases from the surrounding nebula. Alternatively, it could have been caused by an impact from a planet of about ten Earth masses a few million years after Jupiter's formation, which would have disrupted an originally compact Jovian core. Outside the layer of metallic hydrogen lies
3440-424: A cuckoo bird, landing on Mount Thornax. He creates a terrible storm, and when Hera arrives at the mountain and sees the bird, which sits on her lap, she takes pity on it, laying her cloak over it. Zeus then transforms back and takes hold of her; when she refuses to have intercourse with him because of their mother, he promises that she will become his wife. Pausanias similarly refers to Zeus transforming himself into
3655-416: A cuckoo to woo Hera, and identifies the location as Mount Thornax. According to a version from Plutarch , as recorded by Eusebius in his Praeparatio evangelica , Hera is raised by a nymph named Macris on the island of Euboea when Zeus kidnaps her, taking her to Mount Cithaeron , where they find a shady hollow, which serves as a "natural bridal chamber". When Macris comes to look for Hera, Cithaeron,
3870-689: A disk remnant left over from the supernova that produced the pulsar. The first confirmed discovery of an exoplanet orbiting an ordinary main-sequence star occurred on 6 October 1995, when Michel Mayor and Didier Queloz of the University of Geneva announced the detection of 51 Pegasi b , an exoplanet around 51 Pegasi . From then until the Kepler space telescope mission, most of the known exoplanets were gas giants comparable in mass to Jupiter or larger as they were more easily detected. The catalog of Kepler candidate planets consists mostly of planets
4085-462: A faint system of planetary rings that were discovered in 1979 by Voyager 1 and further investigated by the Galileo orbiter in the 1990s. The Jovian ring system consists mainly of dust and has three main segments: an inner torus of particles known as the halo, a relatively bright main ring, and an outer gossamer ring. The rings have a reddish colour in visible and near-infrared light. The age of
4300-469: A fragment of Epimenides, the nymphs Helike and Kynosura are the young Zeus's nurses. Cronus travels to Crete to look for Zeus, who, to conceal his presence, transforms himself into a snake and his two nurses into bears. According to Musaeus , after Zeus is born, Rhea gives him to Themis . Themis in turn gives him to Amalthea, who owns a she-goat, which nurses the young Zeus. Antoninus Liberalis , in his Metamorphoses , says that Rhea gives birth to Zeus in
4515-547: A great alarum", and in doing so deceiving Cronus, and relates that when the Kouretes were carrying the newborn Zeus that the umbilical cord fell away at the river Triton. Hyginus , in his Fabulae , relates a version in which Cronus casts Poseidon into the sea and Hades to the Underworld instead of swallowing them. When Zeus is born, Hera (also not swallowed), asks Rhea to give her the young Zeus, and Rhea gives Cronus
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#17327658030904730-476: A large one in the centre and eight others around it, while its southern counterpart also consists of a centre vortex but is surrounded by five large storms and a single smaller one for a total of 7 storms. In 2000, an atmospheric feature formed in the southern hemisphere that is similar in appearance to the Great Red Spot, but smaller. This was created when smaller, white oval-shaped storms merged to form
4945-442: A list of omens and their relationships with various celestial phenomena including the motions of the planets. The inferior planets Venus and Mercury and the superior planets Mars , Jupiter , and Saturn were all identified by Babylonian astronomers . These would remain the only known planets until the invention of the telescope in early modern times. The ancient Greeks initially did not attach as much significance to
5160-489: A man who was guilty of murdering his father-in-law, by purifying him and bringing him to Olympus. However, Ixion started to lust after Hera. Hera complained about this to her husband, and Zeus decided to test Ixion. Zeus fashioned a cloud that resembles Hera ( Nephele ) and laid the cloud-Hera in Ixion's bed. Ixion coupled with Nephele, resulting in the birth of Centaurus . Zeus punished Ixion for lusting after Hera by tying him to
5375-411: A mass 5.5–10.4 times the mass of Earth, attracted attention upon its discovery for potentially being in the habitable zone, though later studies concluded that it is actually too close to its star to be habitable. Planets more massive than Jupiter are also known, extending seamlessly into the realm of brown dwarfs. Exoplanets have been found that are much closer to their parent star than any planet in
5590-529: A mass of 60.4 M J . Theoretical models indicate that if Jupiter had over 40% more mass, the interior would be so compressed that its volume would decrease despite the increasing amount of matter. For smaller changes in its mass, the radius would not change appreciably. As a result, Jupiter is thought to have about as large a diameter as a planet of its composition and evolutionary history can achieve. The process of further shrinkage with increasing mass would continue until appreciable stellar ignition
5805-479: A metallic or rocky core today, or a reaccumulation of the resulting debris. Every planet began its existence in an entirely fluid state; in early formation, the denser, heavier materials sank to the centre, leaving the lighter materials near the surface. Each therefore has a differentiated interior consisting of a dense planetary core surrounded by a mantle that either is or was a fluid . The terrestrial planets' mantles are sealed within hard crusts , but in
6020-579: A more complex narrative. Typhon is, similarly to in Hesiod, the child of Gaia and Tartarus, produced out of anger at Zeus's defeat of the Giants. The monster attacks heaven, and all of the gods, out of fear, transform into animals and flee to Egypt, except for Zeus, who attacks the monster with his thunderbolt and sickle. Typhon is wounded and retreats to Mount Kasios in Syria, where Zeus grapples with him, giving
6235-524: A multitude of similar-sized objects. As described above, this characteristic was mandated as part of the IAU 's official definition of a planet in August 2006. Although to date this criterion only applies to the Solar System, a number of young extrasolar systems have been found in which evidence suggests orbital clearing is taking place within their circumstellar discs . Gravity causes planets to be pulled into
6450-402: A negligible axial tilt as a result of their proximity to their stars. Similarly, the axial tilts of the planetary-mass moons are near zero, with Earth's Moon at 6.687° as the biggest exception; additionally, Callisto's axial tilt varies between 0 and about 2 degrees on timescales of thousands of years. The planets rotate around invisible axes through their centres. A planet's rotation period
6665-413: A planet reaches a mass somewhat larger than Mars's mass, it begins to accumulate an extended atmosphere , greatly increasing the capture rate of the planetesimals by means of atmospheric drag . Depending on the accretion history of solids and gas, a giant planet , an ice giant , or a terrestrial planet may result. It is thought that the regular satellites of Jupiter, Saturn, and Uranus formed in
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6880-426: A plausible base for future human exploration . Titan has the only nitrogen -rich planetary atmosphere in the Solar System other than Earth's. Just as Earth's conditions are close to the triple point of water, allowing it to exist in all three states on the planet's surface, so Titan's are to the triple point of methane . Planetary atmospheres are affected by the varying insolation or internal energy, leading to
7095-522: A priestess of Hera, who is subsequently turned into a cow, and suffers at Hera's hands: according to Apollodorus, Hera sends a gadfly to sting the cow, driving her all the way to Egypt, where she is finally transformed back into human form. In later accounts of Zeus's affair with Semele , a daughter of Cadmus and Harmonia , Hera tricks her into persuading Zeus to grant her any promise. Semele asks him to come to her as he comes to his own wife Hera, and when Zeus upholds this promise, she dies out of fright and
7310-510: A prophecy from his parents, Gaia and Uranus, that one of his own children is destined to one day overthrow him as he overthrew his father. This causes Rhea "unceasing grief", and upon becoming pregnant with her sixth child, Zeus, she approaches her parents, Gaia and Uranus, seeking a plan to save her child and bring retribution to Cronus. Following her parents' instructions, she travels to Lyctus in Crete , where she gives birth to Zeus, handing
7525-438: A punishing gift to compensate for the boon they had been given. He commands Hephaestus to mold from earth the first woman, a "beautiful evil" whose descendants would torment the human race. After Hephaestus does so, several other gods contribute to her creation. Hermes names the woman ' Pandora '. Pandora was given in marriage to Prometheus's brother Epimetheus . Zeus gave her a jar which contained many evils. Pandora opened
7740-456: A radius of 60,000 km (37,000 mi) (11,000 km (6,800 mi) below the cloud tops) and merge again at 50,000 km (31,000 mi) (22,000 km (14,000 mi) beneath the clouds). Rainfalls of diamonds have been suggested to occur, as well as on Saturn and the ice giants Uranus and Neptune. The temperature and pressure inside Jupiter increase steadily inward as the heat of planetary formation can only escape by convection. At
7955-443: A relatively bright main ring, and an outer gossamer ring. These rings appear to be made of dust, whereas Saturn's rings are made of ice. The main ring is most likely made out of material ejected from the satellites Adrastea and Metis , which is drawn into Jupiter because of the planet's strong gravitational influence. New material is added by additional impacts. In a similar way, the moons Thebe and Amalthea are believed to produce
8170-461: A roughly spherical shape, so a planet's size can be expressed roughly by an average radius (for example, Earth radius or Jupiter radius ). However, planets are not perfectly spherical; for example, the Earth's rotation causes it to be slightly flattened at the poles with a bulge around the equator . Therefore, a better approximation of Earth's shape is an oblate spheroid , whose equatorial diameter
8385-587: A sacred cave in Crete, full of sacred bees, which become the nurses of the infant. While the cave is considered forbidden ground for both mortals and gods, a group of thieves seek to steal honey from it. Upon laying eyes on the swaddling clothes of Zeus, their bronze armour "split[s] away from their bodies", and Zeus would have killed them had it not been for the intervention of the Moirai and Themis ; he instead transforms them into various species of birds. According to
8600-541: A scholion on the Iliad (citing Hesiod and Bacchylides ), when Europa is picking flowers with her female companions in a meadow in Phoenicia, Zeus transforms himself into a bull, lures her from the others, and then carries her across the sea to the island of Crete, where he resumes his usual form to sleep with her. In Euripides ' Helen , Zeus takes the form of a swan, and after being chased by an eagle, finds shelter in
8815-454: A significant impact on mythology , religious cosmology , and ancient astronomy . In ancient times, astronomers noted how certain lights moved across the sky, as opposed to the " fixed stars ", which maintained a constant relative position in the sky. Ancient Greeks called these lights πλάνητες ἀστέρες ( planētes asteres ) ' wandering stars ' or simply πλανῆται ( planētai ) ' wanderers ' from which today's word "planet"
Jupiter - Misplaced Pages Continue
9030-403: A significantly lower mass than the gas giants (only 14 and 17 Earth masses). Dwarf planets are gravitationally rounded, but have not cleared their orbits of other bodies . In increasing order of average distance from the Sun, the ones generally agreed among astronomers are Ceres , Orcus , Pluto , Haumea , Quaoar , Makemake , Gonggong , Eris , and Sedna . Ceres is the largest object in
9245-407: A similar way; however, Triton was likely captured by Neptune, and Earth's Moon and Pluto's Charon might have formed in collisions. When the protostar has grown such that it ignites to form a star, the surviving disk is removed from the inside outward by photoevaporation , the solar wind , Poynting–Robertson drag and other effects. Thereafter there still may be many protoplanets orbiting
9460-528: A single feature—these three smaller white ovals were formed in 1939–1940. The merged feature was named Oval BA . It has since increased in intensity and changed from white to red, earning it the nickname "Little Red Spot". In April 2017, a "Great Cold Spot" was discovered in Jupiter's thermosphere at its north pole . This feature is 24,000 km (15,000 mi) across, 12,000 km (7,500 mi) wide, and 200 °C (360 °F) cooler than surrounding material. While this spot changes form and intensity over
9675-518: A snake and raped her. Rhea became pregnant and gave birth to Persephone . Zeus in the form of a snake would mate with his daughter Persephone, which resulted in the birth of Dionysus . Zeus granted Callirrhoe's prayer that her sons by Alcmaeon , Acarnan and Amphoterus , grow quickly so that they might be able to avenge the death of their father by the hands of Phegeus and his two sons. Both Zeus and Poseidon wooed Thetis , daughter of Nereus . But when Themis (or Prometheus) prophesied that
9890-404: A stone to swallow. Hera gives him to Amalthea, who hangs his cradle from a tree, where he is not in heaven, on earth or in the sea, meaning that when Cronus later goes looking for Zeus, he is unable to find him. Hyginus also says that Ida , Althaea, and Adrasteia , usually considered the children of Oceanus , are sometimes called the daughters of Melisseus and the nurses of Zeus. According to
10105-437: A surface depth where the atmospheric pressure level is 1 bar (0.10 MPa ), the temperature is around 165 K (−108 °C; −163 °F). The region where supercritical hydrogen changes gradually from a molecular fluid to a metallic fluid spans pressure ranges of 50–400 GPa with temperatures of 5,000–8,400 K (4,730–8,130 °C; 8,540–14,660 °F), respectively. The temperature of Jupiter's diluted core
10320-471: A terrestrial planet could sustain liquid water on its surface, given enough atmospheric pressure. One in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone, which suggests that the nearest would be expected to be within 12 light-years distance from Earth. The frequency of occurrence of such terrestrial planets is one of the variables in the Drake equation , which estimates
10535-417: A transparent Indo-European etymology. Plato , in his Cratylus , gives a folk etymology of Zeus meaning "cause of life always to all things", because of puns between alternate titles of Zeus ( Zen and Dia ) with the Greek words for life and "because of". This etymology, along with Plato's entire method of deriving etymologies, is not supported by modern scholarship. Diodorus Siculus wrote that Zeus
10750-402: A transparent interior atmosphere of hydrogen. At this depth, the pressure and temperature are above molecular hydrogen's critical pressure of 1.3 MPa and critical temperature of 33 K (−240.2 °C ; −400.3 °F ). In this state, there are no distinct liquid and gas phases—hydrogen is said to be in a supercritical fluid state. The hydrogen and helium gas extending downward from
10965-476: A tree which produces golden apples as a wedding gift. Eratosthenes and Hyginus attribute a similar story to Pherecydes, in which Hera is amazed by the gift, and asks for the apples to be planted in the "garden of the gods", nearby to Mount Atlas . Apollodorus specifies them as the golden apples of the Hesperides , and says that Gaia gives them to Zeus after the marriage. According to Diodorus Siculus ,
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#173276580309011180-416: A wheel that spins forever. Once, Helios the sun god gave his chariot to his inexperienced son Phaethon to drive. Phaethon could not control his father's steeds so he ended up taking the chariot too high, freezing the earth, or too low, burning everything to the ground. The earth itself prayed to Zeus, and in order to prevent further disaster, Zeus hurled a thunderbolt at Phaethon, killing him and saving
11395-430: A youthful affair between Zeus and Hera. In the Iliad , the pair are described as having first lay with each other before Cronus is sent to Tartarus, without the knowledge of their parents. A scholiast on the Iliad states that, after Cronus is banished to Tartarus, Oceanus and Tethys give Hera to Zeus in marriage, and only shortly after the two are wed, Hera gives birth to Hephaestus , having lay secretly with Zeus on
11610-438: Is 43 kilometers (27 mi) larger than the pole -to-pole diameter. Generally, a planet's shape may be described by giving polar and equatorial radii of a spheroid or specifying a reference ellipsoid . From such a specification, the planet's flattening, surface area, and volume can be calculated; its normal gravity can be computed knowing its size, shape, rotation rate, and mass. A planet's defining physical characteristic
11825-402: Is a gas giant , meaning its chemical composition is primarily hydrogen and helium. These materials are classified as gasses in planetary geology, a term that does not denote the state of matter. It is the largest planet in the Solar System, with a diameter of 142,984 km (88,846 mi) at its equator , giving it a volume 1,321 times that of the Earth. Its average density, 1.326 g/cm,
12040-452: Is about 50 km (31 mi) deep and consists of at least two decks of ammonia clouds: a thin, clearer region on top and a thicker, lower deck. There may be a thin layer of water clouds underlying the ammonia clouds, as suggested by flashes of lightning detected in the atmosphere of Jupiter. These electrical discharges can be up to a thousand times as powerful as lightning on Earth. The water clouds are assumed to generate thunderstorms in
12255-410: Is about ten times larger than Earth ( 11.209 R 🜨 ) and smaller than the Sun ( 0.102 76 R ☉ ). Jupiter's mass is 318 times that of Earth; 2.5 times that of all the other planets in the Solar System combined. It is so massive that its barycentre with the Sun lies above the Sun's surface at 1.068 solar radii from the Sun's centre. Jupiter's radius is about one tenth
12470-682: Is an ancient Greek epic poem attributed to Homer about the Trojan war and the battle over the City of Troy , in which Zeus plays a major part. Scenes in which Zeus appears include: When Hades requested to marry Zeus's daughter, Persephone , Zeus approved and advised Hades to abduct Persephone, as her mother Demeter would not allow her to marry Hades. In the Orphic "Rhapsodic Theogony" (first century BC/AD), Zeus wanted to marry his mother Rhea . After Rhea refused to marry him, Zeus turned into
12685-581: Is approximately two-fifths the orbital period of Saturn, forming a near orbital resonance . The orbital plane of Jupiter is inclined 1.30° compared to Earth. Because the eccentricity of its orbit is 0.049, Jupiter is slightly over 75 million km nearer the Sun at perihelion than aphelion , which means that its orbit is nearly circular. This low eccentricity is at odds with exoplanet discoveries, which have revealed Jupiter-sized planets with very high eccentricities. Models suggest this may be due to there being two giant planets in our Solar System, as
12900-593: Is born, emerging from Zeus's head, but the foretold son never comes forth. Apollodorus presents a similar version, stating that Metis took many forms in attempting to avoid Zeus's embraces, and that it was Gaia alone who warned Zeus of the son who would overthrow him. According to a fragment likely from the Hesiodic corpus, quoted by Chrysippus, it is out of anger at Hera for producing Hephaestus on her own that Zeus has intercourse with Metis, and then swallows her, thereby giving rise to Athena from himself. A scholiast on
13115-561: Is delineated by a set of elements: Planets have varying degrees of axial tilt; they spin at an angle to the plane of their stars' equators. This causes the amount of light received by each hemisphere to vary over the course of its year; when the Northern Hemisphere points away from its star, the Southern Hemisphere points towards it, and vice versa. Each planet therefore has seasons , resulting in changes to
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#173276580309013330-409: Is denser, with a composition of roughly 71% hydrogen, 24% helium, and 5% other elements by mass. The atmospheric proportions of hydrogen and helium are close to the theoretical composition of the primordial solar nebula . Neon in the upper atmosphere consists of 20 parts per million by mass, which is about a tenth as abundant as in the Sun. Jupiter's helium abundance is about 80% that of the Sun due to
13545-414: 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. Planet A planet is a large, rounded astronomical body that
13760-408: Is estimated to be 20,000 K (19,700 °C; 35,500 °F) with a pressure of around 4,000 GPa. The atmosphere of Jupiter is primarily composed of molecular hydrogen and helium, with a smaller amount of other compounds such as water, methane, hydrogen sulfide, and ammonia. Jupiter's atmosphere extends to a depth of approximately 3,000 km (2,000 mi) below the cloud layers. Jupiter
13975-472: Is generally required to be in orbit around a star , stellar remnant , or brown dwarf , and is not one itself. The Solar System has eight planets by the most restrictive definition of the term: the terrestrial planets Mercury , Venus , Earth , and Mars , and the giant planets Jupiter , Saturn , Uranus , and Neptune . The best available theory of planet formation is the nebular hypothesis , which posits that an interstellar cloud collapses out of
14190-424: Is given "ephemeral fruits" by the Moirai , which reduce his strength. The monster then flees to Thrace, where he hurls mountains at Zeus, which are sent back at him by the god's thunderbolts, before, while fleeing to Sicily , Zeus launches Mount Etna upon him, finally ending him. Nonnus , who gives the longest and most detailed account, presents a narrative similar to Apollodorus, with differences such as that it
14405-752: Is his sister Demeter , with whom he has Persephone . Zeus's next consort is the Titan Mnemosyne ; as described at the beginning of the Theogony , Zeus lies with Mnemosyne in Piera each night for nine nights, producing the nine Muses. His sixth wife is the Titan Leto , who bears him the twins Apollo and Artemis , who, according to the Homeric Hymn to Apollo , are born on the island of Delos . In Hesiod's account, Zeus's seventh and final wife
14620-442: Is his sister Hera . While Hera is Zeus's seventh wife in Hesiod's version, in other accounts she is his first and only wife. In the Theogony , the couple has three children, Ares , Hebe , and Eileithyia . While Hesiod states that Hera produces Hephaestus on her own after Athena is born from Zeus's head, other versions, including Homer, have Hephaestus as a child of Zeus and Hera as well. Various authors give descriptions of
14835-612: Is instead Cadmus and Pan who recovers Zeus's sinews, by luring Typhon with music and then tricking him. In the Iliad , Homer tells of another attempted overthrow, in which Hera, Poseidon, and Athena conspire to overpower Zeus and tie him in bonds. It is only because of the Nereid Thetis , who summons Briareus, one of the Hecatoncheires , to Olympus, that the other Olympians abandon their plans (out of fear for Briareus). According to Hesiod, Zeus takes Metis , one of
15050-458: Is known as a stellar day . Most of the planets in the Solar System rotate in the same direction as they orbit the Sun, which is counter-clockwise as seen from above the Sun's north pole . The exceptions are Venus and Uranus, which rotate clockwise, though Uranus's extreme axial tilt means there are differing conventions on which of its poles is "north", and therefore whether it is rotating clockwise or anti-clockwise. Regardless of which convention
15265-664: Is lower than those of the four terrestrial planets . The atmosphere of Jupiter is approximately 76% hydrogen and 24% helium by mass. By volume, the upper atmosphere is about 90% hydrogen and 10% helium, with the lower proportion owing to the individual helium atoms being more massive than the molecules of hydrogen formed in this part of the atmosphere. The atmosphere contains trace amounts of elemental carbon , oxygen , sulfur , and neon , as well as ammonia , water vapour , phosphine , hydrogen sulfide , and hydrocarbons like methane , ethane and benzene . Its outermost layer contains crystals of frozen ammonia. The planet's interior
15480-410: Is not a solid body, its upper atmosphere undergoes differential rotation . The rotation of Jupiter's polar atmosphere is about 5 minutes longer than that of the equatorial atmosphere. The planet is an oblate spheroid, meaning that the diameter across its equator is longer than the diameter measured between its poles . On Jupiter, the equatorial diameter is 9,276 km (5,764 mi) longer than
15695-671: Is perpetually covered with clouds of ammonia crystals, which may contain ammonium hydrosulfide as well. The clouds are located in the tropopause layer of the atmosphere, forming bands at different latitudes, known as tropical regions. These are subdivided into lighter-hued zones and darker belts . The interactions of these conflicting circulation patterns cause storms and turbulence . Wind speeds of 100 metres per second (360 km/h; 220 mph) are common in zonal jet streams . The zones have been observed to vary in width, colour and intensity from year to year, but they have remained stable enough for scientists to name them. The cloud layer
15910-422: Is reduced to ashes. According to Callimachus, after Zeus sleeps with Callisto, Hera turns her into a bear, and instructs Artemis to shoot her. In addition, Zeus's son by Alcmene, the hero Heracles , is persecuted continuously throughout his mortal life by Hera, up until his apotheosis. According to Diodorus Siculus , Alcmene, the mother of Heracles, was the very last mortal woman Zeus ever slept with; following
16125-470: Is that it is massive enough for the force of its own gravity to dominate over the electromagnetic forces binding its physical structure, leading to a state of hydrostatic equilibrium . This effectively means that all planets are spherical or spheroidal. Up to a certain mass, an object can be irregular in shape, but beyond that point, which varies depending on the chemical makeup of the object, gravity begins to pull an object towards its own centre of mass until
16340-451: 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 that of Jupiter , the chief deity of ancient Roman religion . Jupiter was the first of the Sun's planets to form, and its inward migration during the primordial phase of the Solar System affected much of the formation history of
16555-437: Is the largest known detached object , a population that never comes close enough to the Sun to interact with any of the classical planets; the origins of their orbits are still being debated. All nine are similar to terrestrial planets in having a solid surface, but they are made of ice and rock rather than rock and metal. Moreover, all of them are smaller than Mercury, with Pluto being the largest known dwarf planet and Eris being
16770-500: Is the smallest object generally agreed to be a geophysical planet , at about six millionths of Earth's mass, though there are many larger bodies that may not be geophysical planets (e.g. Salacia ). An exoplanet is a planet outside the Solar System. As of 24 July 2024, there are 7,026 confirmed exoplanets in 4,949 planetary systems , with 1007 systems having more than one planet . Known exoplanets range in size from gas giants about twice as large as Jupiter down to just over
16985-421: Is the smallest, at 0.055 Earth masses. The planets of the Solar System can be divided into categories based on their composition. Terrestrials are similar to Earth, with bodies largely composed of rock and metal: Mercury, Venus, Earth, and Mars. Earth is the largest terrestrial planet. Giant planets are significantly more massive than the terrestrials: Jupiter, Saturn, Uranus, and Neptune. They differ from
17200-446: Is the strongest of any planet in the Solar System, with a dipole moment of 4.170 gauss (0.4170 mT ) that is tilted at an angle of 10.31° to the pole of rotation. The surface magnetic field strength varies from 2 gauss (0.20 mT) up to 20 gauss (2.0 mT). This field is thought to be generated by eddy currents —swirling movements of conducting materials—within the fluid, metallic hydrogen core. At about 75 Jupiter radii from
17415-457: Is used, Uranus has a retrograde rotation relative to its orbit. The rotation of a planet can be induced by several factors during formation. A net angular momentum can be induced by the individual angular momentum contributions of accreted objects. The accretion of gas by the giant planets contributes to the angular momentum. Finally, during the last stages of planet building, a stochastic process of protoplanetary accretion can randomly alter
17630-568: The Iliad , in contrast, states that when Zeus swallows her, Metis is pregnant with Athena not by Zeus himself, but by the Cyclops Brontes. The motif of Zeus swallowing Metis can be seen as a continuation of the succession myth: it is prophesied that a son of Zeus will overthrow him, just as he overthrew his father, but whereas Cronos met his end because he did not swallow the real Zeus, Zeus holds onto his power because he successfully swallows
17845-544: 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
18060-471: 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
18275-689: The Cyclopes , who, in return, and out of gratitude, give him his thunderbolt, which had previously been hidden by Gaia. Then begins the Titanomachy , the war between the Olympians, led by Zeus, and the Titans, led by Cronus, for control of the universe, with Zeus and the Olympians fighting from Mount Olympus , and the Titans fighting from Mount Othrys . The battle lasts for ten years with no clear victor emerging, until, upon Gaia's advice, Zeus releases
18490-648: The Giants , who fight the Olympian gods in a battle known as the Gigantomachy. According to Hesiod, the Giants are the offspring of Gaia, born from the drops of blood that fell on the ground when Cronus castrated his father Uranus; there is, however, no mention of a battle between the gods and the Giants in the Theogony . It is Apollodorus who provides the most complete account of the Gigantomachy. He says that Gaia, out of anger at how Zeus had imprisoned her children,
18705-619: The Hundred-Handers , who (similarly to the Cyclopes) were imprisoned beneath the Earth's surface. He gives them nectar and ambrosia and revives their spirits, and they agree to aid him in the war. Zeus then launches his final attack on the Titans, hurling bolts of lightning upon them while the Hundred-Handers attack with barrages of rocks, and the Titans are finally defeated, with Zeus banishing them to Tartarus and assigning
18920-613: The Kuiper belt . The discovery of other large objects in the Kuiper belt, particularly Eris , spurred debate about how exactly to define a planet. In 2006, the International Astronomical Union (IAU) adopted a definition of a planet in the Solar System, placing the four terrestrial planets and the four giant planets in the planet category; Ceres, Pluto, and Eris are in the category of dwarf planet . Many planetary scientists have nonetheless continued to apply
19135-546: The Middle Ages , has come to mean 'happy' or 'merry', moods ascribed to Jupiter's influence in astrology . The original Greek deity Zeus supplies the root zeno- , which is used to form some Jupiter-related words, such as zenography . Jupiter is believed to be the oldest planet in the Solar System, having formed just one million years after the Sun and roughly 50 million years before Earth. Current models of Solar System formation suggest that Jupiter formed at or beyond
19350-537: The Muses . He was respected as a sky father who was chief of the gods and assigned roles to the others: "Even the gods who are not his natural children address him as Father, and all the gods rise in his presence." He was equated with many foreign weather gods , permitting Pausanias to observe "That Zeus is king in heaven is a saying common to all men". Zeus's symbols are the thunderbolt , eagle , bull , and oak . In addition to his Indo-European inheritance ,
19565-461: The Oceanid daughters of Oceanus and Tethys , as his first wife. However, when she is about to give birth to a daughter, Athena , he swallows her whole upon the advice of Gaia and Uranus, as it had been foretold that after bearing a daughter, she would give birth to a son, who would overthrow him as king of gods and mortals; it is from this position that Metis gives counsel to Zeus. In time, Athena
19780-552: The Proto-Indo-European vocative * dyeu-ph 2 tēr ), deriving from the root * dyeu - ("to shine", and in its many derivatives, "sky, heaven, god"). Albanian Zoj-z and Messapic Zis are clear equivalents and cognates of Zeus . In the Greek, Albanian, and Messapic forms the original cluster *di̯ underwent affrication to *dz . Zeus is the only deity in the Olympic pantheon whose name has such
19995-433: The Theogony , after Zeus reaches manhood, Cronus is made to disgorge the five children and the stone "by the stratagems of Gaia, but also by the skills and strength of Zeus", presumably in reverse order, vomiting out the stone first, then each of the five children in the opposite order to swallowing. Zeus then sets up the stone at Delphi , so that it may act as "a sign thenceforth and a marvel to mortal men". Zeus next frees
20210-423: The asteroid belt , located between the orbits of Mars and Jupiter. The other eight all orbit beyond Neptune. Orcus, Pluto, Haumea, Quaoar, and Makemake orbit in the Kuiper belt , which is a second belt of small Solar System bodies beyond the orbit of Neptune. Gonggong and Eris orbit in the scattered disc , which is somewhat further out and, unlike the Kuiper belt, is unstable towards interactions with Neptune. Sedna
20425-454: The climate over the course of its year. The time at which each hemisphere points farthest or nearest from its star is known as its solstice . Each planet has two in the course of its orbit; when one hemisphere has its summer solstice with its day being the longest, the other has its winter solstice when its day is shortest. The varying amount of light and heat received by each hemisphere creates annual changes in weather patterns for each half of
20640-485: The oracle of Dodona , his consort was said to be Dione , by whom the Iliad states that he fathered Aphrodite . According to the Theogony , Zeus's first wife was Metis , by whom he had Athena . Zeus was also infamous for his erotic escapades. These resulted in many divine and heroic offspring, including Apollo , Artemis , Hermes , Persephone , Dionysus , Perseus , Heracles , Helen of Troy , Minos , and
20855-601: The precipitation of these elements as helium-rich droplets, a process that happens deep in the planet's interior. Based on spectroscopy , Saturn is thought to be similar in composition to Jupiter, but the other giant planets Uranus and Neptune have relatively less hydrogen and helium and relatively more of the next most common elements , including oxygen, carbon, nitrogen, and sulfur. These planets are known as ice giants because during their formation, these elements are thought to have been incorporated into them as ice; however, they probably contain very little ice. Jupiter
21070-400: The snow line : a distance from the early Sun where the temperature was sufficiently cold for volatiles such as water to condense into solids. First forming a solid core, the planet then accumulated its gaseous atmosphere. Therefore, the planet must have formed before the solar nebula was fully dispersed. During its formation, Jupiter's mass gradually increased until it had 20 times the mass of
21285-517: The tutelary deity of the mountain, stops her, saying that Zeus is sleeping there with Leto. Photius , in his Bibliotheca , tells us that in Ptolemy Hephaestion 's New History , Hera refuses to lay with Zeus, and hides in a cave to avoid him, before an earthborn man named Achilles convinces her to marry Zeus, leading to the pair first sleeping with each other. According to Stephanus of Byzantium , Zeus and Hera first lay together at
21500-400: The 16th and 17th centuries. With the development of the telescope , the meaning of planet broadened to include objects only visible with assistance: the moons of the planets beyond Earth; the ice giants Uranus and Neptune; Ceres and other bodies later recognized to be part of the asteroid belt ; and Pluto , later found to be the largest member of the collection of icy bodies known as
21715-446: The Earth, approximately half of which was made up of silicates, ices and other heavy-element constituents. When the proto-Jupiter grew larger than 50 Earth masses it created a gap in the solar nebula. Thereafter, the growing planet reached its final mass in 3–4 million years. Since Jupiter is made of the same elements as the Sun (hydrogen and helium) it has been suggested that the Solar System might have been early in its formation
21930-584: The Homeric "cloud collector" was the god of the sky and thunder like his Near-Eastern counterparts, he was also the supreme cultural artifact; in some senses, he was the embodiment of Greek religious beliefs and the archetypal Greek deity. Popular conceptions of Zeus differed widely from place to place. Local varieties of Zeus often have little in common with each other except the name. They exercised different areas of authority and were worshiped in different ways; for example, some local cults conceived of Zeus as
22145-695: The Hundred-Handers the task of acting as their warders. Apollodorus provides a similar account, saying that, when Zeus reaches adulthood, he enlists the help of the Oceanid Metis , who gives Cronus an emetic , forcing to him to disgorge the stone and Zeus's five siblings. Zeus then fights a similar ten-year war against the Titans, until, upon the prophesying of Gaia, he releases the Cyclopes and Hundred-Handers from Tartarus, first slaying their warder, Campe . The Cyclopes give him his thunderbolt, Poseidon his trident and Hades his helmet of invisibility, and
22360-672: The Lydian , considered Zeus to have been born in Lydia , while the Alexandrian poet Callimachus (c. 310 – c. 240 BC), in his Hymn to Zeus , says that he was born in Arcadia . Diodorus Siculus (fl. 1st century BC) seems at one point to give Mount Ida as his birthplace, but later states he is born in Dicte , and the mythographer Apollodorus (first or second century AD) similarly says he
22575-631: The Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn. After the fall of the Western Roman Empire , astronomy developed further in India and the medieval Islamic world. In 499 CE, the Indian astronomer Aryabhata propounded a planetary model that explicitly incorporated Earth's rotation about its axis, which he explains as the cause of what appears to be an apparent westward motion of
22790-588: The Moon. The smallest object in the Solar System generally agreed to be a geophysical planet is Saturn's moon Mimas, with a radius about 3.1% of Earth's and a mass about 0.00063% of Earth's. Saturn's smaller moon Phoebe , currently an irregular body of 1.7% Earth's radius and 0.00014% Earth's mass, is thought to have attained hydrostatic equilibrium and differentiation early in its history before being battered out of shape by impacts. Some asteroids may be fragments of protoplanets that began to accrete and differentiate, but suffered catastrophic collisions, leaving only
23005-452: The Solar System is to the Sun. Mercury, the closest planet to the Sun at 0.4 AU , takes 88 days for an orbit, but ultra-short period planets can orbit in less than a day. The Kepler-11 system has five of its planets in shorter orbits than Mercury's, all of them much more massive than Mercury. There are hot Jupiters , such as 51 Pegasi b, that orbit very close to their star and may evaporate to become chthonian planets , which are
23220-404: The Solar System planets except Mercury have substantial atmospheres because their gravity is strong enough to keep gases close to the surface. Saturn's largest moon Titan also has a substantial atmosphere thicker than that of Earth; Neptune's largest moon Triton and the dwarf planet Pluto have more tenuous atmospheres. The larger giant planets are massive enough to keep large amounts of
23435-437: The Solar System, but in multitudes of other extrasolar systems. The consensus as to what counts as a planet, as opposed to other objects, has changed several times. It previously encompassed asteroids , moons , and dwarf planets like Pluto , and there continues to be some disagreement today. The five classical planets of the Solar System , being visible to the naked eye, have been known since ancient times and have had
23650-489: The Solar System, whereas others are commonly observed in exoplanets. In the Solar System, all the planets orbit the Sun in the same direction as the Sun rotates : counter-clockwise as seen from above the Sun's north pole. At least one exoplanet, WASP-17b , has been found to orbit in the opposite direction to its star's rotation. The period of one revolution of a planet's orbit is known as its sidereal period or year . A planet's year depends on its distance from its star;
23865-527: The Sun, and possibly even outside the argon snow line, which may be as far as 40 AU (6.0 billion km; 3.7 billion mi). Having formed at one of these extreme distances, Jupiter would then have, over a roughly 700,000-year period, migrated inwards to its current location, during an epoch approximately 2–3 million years after the planet began to form. In this model, Saturn, Uranus, and Neptune would have formed even further out than Jupiter, and Saturn would also have migrated inwards. Jupiter
24080-403: The Sun. As the young planet accreted mass, its interaction with the gas disk orbiting the Sun and the orbital resonances from Saturn caused it to migrate inward. This upset the orbits of several super-Earths orbiting closer to the Sun, causing them to collide destructively. Saturn would later have begun to migrate inwards at a faster rate than Jupiter until the two planets became captured in
24295-476: The Sun. The mean apparent magnitude is −2.20 with a standard deviation of 0.33. The angular diameter of Jupiter likewise varies from 50.1 to 30.5 arc seconds . Favourable oppositions occur when Jupiter is passing through the perihelion of its orbit, bringing it closer to Earth. Near opposition, Jupiter will appear to go into retrograde motion for a period of about 121 days, moving backward through an angle of 9.9° before returning to prograde movement. Because
24510-439: The Titans and banishes them to Tartarus, his rule is challenged by the monster Typhon , a giant serpentine creature who battles Zeus for control of the cosmos. According to Hesiod, Typhon is the offspring of Gaia and Tartarus , described as having a hundred snaky fire-breathing heads. Hesiod says he "would have come to reign over mortals and immortals" had it not been for Zeus noticing the monster and dispatching with him quickly:
24725-467: The Titans are defeated and the Hundred-Handers made their guards. According to the Iliad , after the battle with the Titans, Zeus shares the world with his brothers, Poseidon and Hades, by drawing lots: Zeus receives the sky, Poseidon the sea, and Hades the underworld, with the earth and Olympus remaining common ground. Upon assuming his place as king of the cosmos, Zeus's rule is quickly challenged. The first of these challenges to his power comes from
24940-406: The Titans, bore the Giants to Uranus. There comes to the gods a prophecy that the Giants cannot be defeated by the gods on their own, but can be defeated only with the help of a mortal; Gaia, upon hearing of this, seeks a special pharmakon (herb) that will prevent the Giants from being killed. Zeus, however, orders Eos (Dawn), Selene (Moon) and Helios (Sun) to stop shining, and harvests all of
25155-529: The ancient Greek and Roman civilizations, Jupiter was named after the chief god of the divine pantheon : Zeus to the Greeks and Jupiter to the Romans. The International Astronomical Union formally adopted the name Jupiter for the planet in 1976 and has since named its newly discovered satellites for the god's lovers, favourites, and descendants. The planetary symbol for Jupiter, [REDACTED] , descends from
25370-480: The atmospheric dynamics that affect the day-night temperature difference are complex. One important characteristic of the planets is their intrinsic magnetic moments , which in turn give rise to magnetospheres. The presence of a magnetic field indicates that the planet is still geologically alive. In other words, magnetized planets have flows of electrically conducting material in their interiors, which generate their magnetic fields. These fields significantly change
25585-408: The background of the stars—namely, Mercury, Venus, Mars, Jupiter, and Saturn. Planets have historically had religious associations: multiple cultures identified celestial bodies with gods, and these connections with mythology and folklore persist in the schemes for naming newly discovered Solar System bodies. Earth itself was recognized as a planet when heliocentrism supplanted geocentrism during
25800-412: The better portions. He sacrificed a large ox , and divided it into two piles. In one pile he put all the meat and most of the fat, covering it with the ox's grotesque stomach, while in the other pile, he dressed up the bones with fat. Prometheus then invited Zeus to choose; Zeus chose the pile of bones. This set a precedent for sacrifices, where humans will keep the fat for themselves and burn the bones for
26015-449: The birth of Heracles, he ceased to beget humans altogether, and fathered no more children. The following is a list of Zeus's offspring, by various mothers. Beside each offspring, the earliest source to record the parentage is given, along with the century to which the source dates. When the gods met at Mecone to discuss which portions they will receive after a sacrifice, the titan Prometheus decided to trick Zeus so that humans receive
26230-428: The bridal clothing; she is so relieved that the couple are reconciled. According to a version from Plutarch, as recorded by Eusebius in his Praeparatio evangelica , when Hera is angry with her husband, she retreats instead to Cithaeron, and Zeus goes to the earth-born man Alalcomeneus, who suggests he pretend to marry someone else. With the help of Alalcomeneus, Zeus creates a wooden statue from an oak tree, dresses it as
26445-409: The cave and beat their spears on their shields so that Cronus cannot hear the infant's crying. Diodorus Siculus provides a similar account, saying that, after giving birth, Rhea travels to Mount Ida and gives the newborn Zeus to the Kouretes, who then takes him to some nymphs (not named), who raised him on a mixture of honey and milk from the goat Amalthea. He also refers to the Kouretes "rais[ing]
26660-468: The chromophores from view. Jupiter has a low axial tilt , thus ensuring that the poles always receive less solar radiation than the planet's equatorial region. Convection within the interior of the planet transports energy to the poles, balancing out temperatures at the cloud layer. A well-known feature of Jupiter is the Great Red Spot , a persistent anticyclonic storm located 22° south of
26875-424: The city of Hermione , having come there from Crete. Callimachus, in a fragment from his Aetia , also apparently makes reference to the couple's union occurring at Naxos . Though no complete account of Zeus and Hera's wedding exists, various authors make reference to it. According to a scholiast on Apollonius of Rhodes ' Argonautica , Pherecydes states that when Zeus and Hera are being married, Gaia brings
27090-458: The classical "cloud-gatherer" ( Greek : Νεφεληγερέτα , Nephelēgereta ) also derives certain iconographic traits from the cultures of the ancient Near East , such as the scepter . The god's name in the nominative is Ζεύς ( Zeús ). It is inflected as follows: vocative : Ζεῦ ( Zeû ); accusative : Δία ( Día ); genitive : Διός ( Diós ); dative : Διί ( Dií ). Diogenes Laërtius quotes Pherecydes of Syros as spelling
27305-473: The cloud layer gradually transitions to a liquid in deeper layers, possibly resembling something akin to an ocean of liquid hydrogen and other supercritical fluids. Physically, the gas gradually becomes hotter and denser as depth increases. Rain-like droplets of helium and neon precipitate downward through the lower atmosphere, depleting the abundance of these elements in the upper atmosphere. Calculations suggest that helium drops separate from metallic hydrogen at
27520-559: The collapse of a nebula into a thin disk of gas and dust. A protostar forms at the core, surrounded by a rotating protoplanetary disk . Through accretion (a process of sticky collision) dust particles in the disk steadily accumulate mass to form ever-larger bodies. Local concentrations of mass known as planetesimals form, and these accelerate the accretion process by drawing in additional material by their gravitational attraction. These concentrations become ever denser until they collapse inward under gravity to form protoplanets . After
27735-406: The definition, regarding where exactly to draw the line between a planet and a star. Multiple exoplanets have been found to orbit in the habitable zones of their stars (where liquid water can potentially exist on a planetary surface ), but Earth remains the only planet known to support life . It is not known with certainty how planets are formed. The prevailing theory is that they coalesce during
27950-473: The eight planets in the Solar System, only Venus and Mars lack such a magnetic field. Of the magnetized planets, the magnetic field of Mercury is the weakest and is barely able to deflect the solar wind . Jupiter's moon Ganymede has a magnetic field several times stronger, and Jupiter's is the strongest in the Solar System (so intense in fact that it poses a serious health risk to future crewed missions to all its moons inward of Callisto ). The magnetic fields of
28165-492: The equator. It was first observed in 1831, and possibly as early as 1665. Images by the Hubble Space Telescope have shown two more "red spots" adjacent to the Great Red Spot. The storm is visible through Earth-based telescopes with an aperture of 12 cm or larger. The storm rotates counterclockwise, with a period of about six days. The maximum altitude of this storm is about 8 km (5 mi) above
28380-418: The farther a planet is from its star, the longer the distance it must travel and the slower its speed, since it is less affected by its star's gravity . No planet's orbit is perfectly circular, and hence the distance of each from the host star varies over the course of its year. The closest approach to its star is called its periastron , or perihelion in the Solar System, whereas its farthest separation from
28595-493: The formation of Jupiter with orbital properties that are close to those of the present-day planet. Other models predict Jupiter forming at distances much farther out, such as 18 AU (2.7 billion km; 1.7 billion mi). According to the Nice model , the infall of proto- Kuiper belt objects over the first 600 million years of Solar System history caused Jupiter and Saturn to migrate from their initial positions into
28810-409: The formation of dynamic weather systems such as hurricanes (on Earth), planet-wide dust storms (on Mars), a greater-than-Earth-sized anticyclone on Jupiter (called the Great Red Spot ), and holes in the atmosphere (on Neptune). Weather patterns detected on exoplanets include a hot region on HD 189733 b twice the size of the Great Red Spot, as well as clouds on the hot Jupiter Kepler-7b ,
29025-626: The giant planets have numerous moons in complex planetary-type systems. Except for Ceres and Sedna, all the consensus dwarf planets are known to have at least one moon as well. Many moons of the giant planets have features similar to those on the terrestrial planets and dwarf planets, and some have been studied as possible abodes of life (especially Europa and Enceladus). The four giant planets are orbited by planetary rings of varying size and complexity. The rings are composed primarily of dust or particulate matter, but can host tiny ' moonlets ' whose gravity shapes and maintains their structure. Although
29240-467: The giant planets the mantle simply blends into the upper cloud layers. The terrestrial planets have cores of elements such as iron and nickel and mantles of silicates . Jupiter and Saturn are believed to have cores of rock and metal surrounded by mantles of metallic hydrogen . Uranus and Neptune, which are smaller, have rocky cores surrounded by mantles of water, ammonia , methane , and other ices . The fluid action within these planets' cores creates
29455-436: The gods on Mount Olympus . His name is cognate with the first syllable of his Roman equivalent Jupiter . Zeus is the child of Cronus and Rhea , the youngest of his siblings to be born, though sometimes reckoned the eldest as the others required disgorging from Cronus's stomach. In most traditions, he is married to Hera , by whom he is usually said to have fathered Ares , Eileithyia , Hebe , and Hephaestus . At
29670-453: The gods. Zeus, enraged at Prometheus's deception, prohibited the use of fire by humans. Prometheus, however, stole fire from Olympus in a fennel stalk and gave it to humans. This further enraged Zeus, who punished Prometheus by binding him to a cliff, where an eagle constantly ate Prometheus's liver, which regenerated every night. Prometheus was eventually freed from his misery by Heracles . Now Zeus, angry at humans, decides to give humanity
29885-417: The grounds that the internal physics of objects does not change between approximately one Saturn mass (beginning of significant self-compression) and the onset of hydrogen burning and becoming a red dwarf star. Beyond roughly 13 M J (at least for objects with solar-type isotopic abundance ), an object achieves conditions suitable for nuclear fusion of deuterium : this has sometimes been advocated as
30100-409: The herb himself, before having Athena summon Heracles . In the conflict, Porphyrion , one of the most powerful of the Giants, launches an attack upon Heracles and Hera; Zeus, however, causes Porphyrion to become lustful for Hera, and when he is just about to violate her, Zeus strikes him with his thunderbolt, before Heracles deals the fatal blow with an arrow. In the Theogony , after Zeus defeats
30315-511: The hydrogen. The orange and brown colours in the clouds of Jupiter are caused by upwelling compounds that change colour when they are exposed to ultraviolet light from the Sun. The exact makeup remains uncertain, but the substances are thought to be made up of phosphorus, sulfur or possibly hydrocarbons. These colourful compounds, known as chromophores , mix with the warmer clouds of the lower deck. The light-coloured zones are formed when rising convection cells form crystallising ammonia that hides
30530-469: The inner solar system eventually allowed the inner planets—including Earth—to form from the rubble. There are several unresolved issues with the grand tack hypothesis. The resulting formation timescales of terrestrial planets appear to be inconsistent with the measured elemental composition. Jupiter would likely have settled into an orbit much closer to the Sun if it had migrated through the solar nebula . Some competing models of Solar System formation predict
30745-416: The interaction of the planet and solar wind. A magnetized planet creates a cavity in the solar wind around itself called the magnetosphere, which the wind cannot penetrate. The magnetosphere can be much larger than the planet itself. In contrast, non-magnetized planets have only small magnetospheres induced by interaction of the ionosphere with the solar wind, which cannot effectively protect the planet. Of
30960-459: The island of Samos beforehand; to conceal this act, she claimed that she had produced Hephaestus on her own. According to another scholiast on the Iliad , Callimachus , in his Aetia , says that Zeus lay with Hera for three hundred years on the island of Samos. According to a scholion on Theocritus ' Idylls , Zeus, one day seeing Hera walking apart from the other gods, becomes intent on having intercourse with her, and transforms himself into
31175-431: The jar and released all the evils, which made mankind miserable. Only hope remained inside the jar. When Zeus was atop Mount Olympus he was appalled by human sacrifice and other signs of human decadence. He decided to wipe out mankind and flooded the world with the help of his brother Poseidon . After the flood, only Deucalion and Pyrrha remained. This flood narrative is a common motif in mythology. The Iliad
31390-474: The lap of Leda , subsequently seducing her, while in Euripides's lost play Antiope , Zeus apparently took the form of a satyr to sleep with Antiope . Various authors speak of Zeus raping Callisto , one of the companions of Artemis , doing so in the form of Artemis herself according to Ovid (or, as mentioned by Apollodorus, in the form of Apollo ), and Pherecydes relates that Zeus sleeps with Alcmene ,
31605-516: The late 1800s showed it to be approximately 41,000 km (25,500 mi) across. As of 2015, the storm was measured at approximately 16,500 by 10,940 km (10,250 by 6,800 mi), and was decreasing in length by about 930 km (580 mi) per year. In October 2021, a Juno flyby mission measured the depth of the Great Red Spot, putting it at around 300–500 kilometres (190–310 miles). Juno missions found several cyclone groups at Jupiter's poles. The northern group contains nine cyclones, with
31820-520: The leftover cores. There are also exoplanets that are much farther from their star. Neptune is 30 AU from the Sun and takes 165 years to orbit, but there are exoplanets that are thousands of AU from their star and take more than a million years to orbit (e.g. COCONUTS-2b ). Although each planet has unique physical characteristics, a number of broad commonalities do exist among them. Some of these characteristics, such as rings or natural satellites, have only as yet been observed in planets in
32035-447: The light gases hydrogen and helium, whereas the smaller planets lose these gases into space . Analysis of exoplanets suggests that the threshold for being able to hold on to these light gases occurs at about 2.0 +0.7 −0.6 M E , so that Earth and Venus are near the maximum size for rocky planets. The composition of Earth's atmosphere is different from the other planets because the various life processes that have transpired on
32250-508: The likelihood that a star will have planets. Hence, a metal-rich population I star is more likely to have a substantial planetary system than a metal-poor, population II star . According to the IAU definition , there are eight planets in the Solar System, which are (in increasing distance from the Sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Jupiter is the largest, at 318 Earth masses , whereas Mercury
32465-460: The location of the marriage is in the land of the Knossians , nearby to the river Theren, while Lactantius attributes to Varro the statement that the couple are married on the island of Samos. There exist several stories in which Zeus, receiving advice, is able to reconcile with an angered Hera. According to Pausanias, Hera, angry with her husband, retreats to the island of Euboea, where she
32680-480: The magnetosphere of an orbiting hot Jupiter. Several planets or dwarf planets in the Solar System (such as Neptune and Pluto) have orbital periods that are in resonance with each other or with smaller bodies. This is common in satellite systems (e.g. the resonance between Io, Europa , and Ganymede around Jupiter, or between Enceladus and Dione around Saturn). All except Mercury and Venus have natural satellites , often called "moons". Earth has one, Mars has two, and
32895-399: The magnetosphere, which protects them from solar wind. The volcanoes on the moon Io emit large amounts of sulfur dioxide , forming a gas torus along its orbit. The gas is ionized in Jupiter's magnetosphere , producing sulfur and oxygen ions . They, together with hydrogen ions originating from the atmosphere of Jupiter, form a plasma sheet in Jupiter's equatorial plane. The plasma in
33110-520: The monster a chance to wrap him in his coils, and rip out the sinews from his hands and feet. Disabled, Zeus is taken by Typhon to the Corycian Cave in Cilicia, where he is guarded by the "she-dragon" Delphyne . Hermes and Aegipan , however, steal back Zeus's sinews, and refit them, reviving him and allowing him to return to the battle, pursuing Typhon, who flees to Mount Nysa; there, Typhon
33325-582: The most massive. There are at least nineteen planetary-mass moons or satellite planets—moons large enough to take on ellipsoidal shapes: The Moon, Io, and Europa have compositions similar to the terrestrial planets; the others are made of ice and rock like the dwarf planets, with Tethys being made of almost pure ice. Europa is often considered an icy planet, though, because its surface ice layer makes it difficult to study its interior. Ganymede and Titan are larger than Mercury by radius, and Callisto almost equals it, but all three are much less massive. Mimas
33540-413: The most obvious result of this is the Great Red Spot , a giant storm that has been recorded since 1831. Jupiter's magnetic field is the strongest and second-largest contiguous structure in the Solar System, generated by eddy currents within the fluid, metallic hydrogen core. The solar wind interacts with the magnetosphere , extending it outward and affecting Jupiter's orbit. Jupiter is surrounded by
33755-400: The myth of Zeus. In Hesiod 's Theogony (c. 730 – 700 BC), Cronus , after castrating his father Uranus , becomes the supreme ruler of the cosmos, and weds his sister Rhea , by whom he begets three daughters and three sons: Hestia , Demeter , Hera , Hades , Poseidon , and lastly, "wise" Zeus, the youngest of the six. He swallows each child as soon as they are born, having received
33970-681: The name Ζάς . The earliest attested forms of the name are the Mycenaean Greek 𐀇𐀸 , di-we (dative) and 𐀇𐀺 , di-wo (genitive), written in the Linear B syllabic script. Zeus is the Greek continuation of * Di̯ēus , the name of the Proto-Indo-European god of the daytime sky, also called * Dyeus ph 2 tēr ("Sky Father"). The god is known under this name in the Rigveda ( Vedic Sanskrit Dyaus/Dyaus Pita ), Latin (compare Jupiter , from Iuppiter , deriving from
34185-450: The newborn child over to Gaia for her to raise, and Gaia takes him to a cave on Mount Aegaeon (Aegeum). Rhea then gives to Cronus, in the place of a child, a stone wrapped in swaddling clothes, which he promptly swallows, unaware that it is not his son. While Hesiod gives Lyctus as Zeus's birthplace, he is the only source to do so, and other authors give different locations. The poet Eumelos of Corinth (8th century BC), according to John
34400-548: The number of intelligent, communicating civilizations that exist in the Milky Way. There are types of planets that do not exist in the Solar System: super-Earths and mini-Neptunes , which have masses between that of Earth and Neptune. Objects less than about twice the mass of Earth are expected to be rocky like Earth; beyond that, they become a mixture of volatiles and gas like Neptune. The planet Gliese 581c , with
34615-414: The object collapses into a sphere. Mass is the prime attribute by which planets are distinguished from stars. No objects between the masses of the Sun and Jupiter exist in the Solar System, but there are exoplanets of this size. The lower stellar mass limit is estimated to be around 75 to 80 times that of Jupiter ( M J ). Some authors advocate that this be used as the upper limit for planethood, on
34830-604: The orbit of Jupiter is outside that of Earth, the phase angle of Jupiter as viewed from Earth is always less than 11.5°; thus, Jupiter always appears nearly fully illuminated when viewed through Earth-based telescopes. It was during spacecraft missions to Jupiter that crescent views of the planet were obtained. A small telescope will usually show Jupiter's four Galilean moons and the cloud belts across Jupiter's atmosphere . A larger telescope with an aperture of 4–6 inches (10–15 cm) will show Jupiter's Great Red Spot when it faces Earth. Observation of Jupiter dates back to at least
35045-401: The origins of planetary rings are not precisely known, they are believed to be the result of natural satellites that fell below their parent planets' Roche limits and were torn apart by tidal forces . The dwarf planets Haumea and Quaoar also have rings. No secondary characteristics have been observed around exoplanets. The sub-brown dwarf Cha 110913−773444 , which has been described as
35260-490: The other giant planets, measured at their surfaces, are roughly similar in strength to that of Earth, but their magnetic moments are significantly larger. The magnetic fields of Uranus and Neptune are strongly tilted relative to the planets' rotational axes and displaced from the planets' centres. In 2003, a team of astronomers in Hawaii observing the star HD 179949 detected a bright spot on its surface, apparently created by
35475-764: The other in perpetual night. Mercury and Venus, the closest planets to the Sun, similarly exhibit very slow rotation: Mercury is tidally locked into a 3:2 spin–orbit resonance (rotating three times for every two revolutions around the Sun), and Venus's rotation may be in equilibrium between tidal forces slowing it down and atmospheric tides created by solar heating speeding it up. All the large moons are tidally locked to their parent planets; Pluto and Charon are tidally locked to each other, as are Eris and Dysnomia, and probably Orcus and its moon Vanth . The other dwarf planets with known rotation periods rotate faster than Earth; Haumea rotates so fast that it has been distorted into
35690-422: The other planets. Jupiter's atmosphere consists of 76% hydrogen and 24% helium by mass, with a denser interior. It contains trace elements like carbon , oxygen , sulfur , neon , ammonia , water vapour , phosphine , hydrogen sulfide , and hydrocarbons . Jupiter's helium abundance is 80% of the Sun's, similar to Saturn 's composition. The ongoing contraction of Jupiter's interior generates more heat than
35905-462: The planet collapsed directly from the gaseous protoplanetary disk , it was expected to completely lack a core, consisting instead of a denser and denser fluid (predominantly molecular and metallic hydrogen) all the way to the centre. Data from the Juno mission showed that Jupiter has a diffuse core that mixes into its mantle, extending for 30–50% of the planet's radius, and comprising heavy elements with
36120-420: The planet have introduced free molecular oxygen . The atmospheres of Mars and Venus are both dominated by carbon dioxide , but differ drastically in density: the average surface pressure of Mars's atmosphere is less than 1% that of Earth's (too low to allow liquid water to exist), while the average surface pressure of Venus's atmosphere is about 92 times that of Earth's. It is likely that Venus's atmosphere
36335-455: 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 rate of rotation, one turn in ten hours, Jupiter is an oblate spheroid ; it has 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;
36550-457: The planet, the interaction of the magnetosphere with the solar wind generates a bow shock . Surrounding Jupiter's magnetosphere is a magnetopause , located at the inner edge of a magnetosheath —a region between it and the bow shock. The solar wind interacts with these regions, elongating the magnetosphere on Jupiter's lee side and extending it outward until it nearly reaches the orbit of Saturn. The four largest moons of Jupiter all orbit within
36765-529: 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
36980-597: The planet. Jupiter's axial tilt is very small, so its seasonal variation is minimal; Uranus, on the other hand, has an axial tilt so extreme it is virtually on its side, which means that its hemispheres are either continually in sunlight or continually in darkness around the time of its solstices . In the Solar System, Mercury, Venus, Ceres, and Jupiter have very small tilts; Pallas, Uranus, and Pluto have extreme ones; and Earth, Mars, Vesta, Saturn, and Neptune have moderate ones. Among exoplanets, axial tilts are not known for certain, though most hot Jupiters are believed to have
37195-589: The planets as the Babylonians. In the 6th and 5th centuries BC, the Pythagoreans appear to have developed their own independent planetary theory , which consisted of the Earth, Sun, Moon, and planets revolving around a "Central Fire" at the center of the Universe. Pythagoras or Parmenides is said to have been the first to identify the evening star ( Hesperos ) and morning star ( Phosphoros ) as one and
37410-404: The polar diameter. Three systems are used as frames of reference for tracking planetary rotation, particularly when graphing the motion of atmospheric features. System I applies to latitudes from 7° N to 7° S; its period is the planet's shortest, at 9h 50 m 30.0s. System II applies at latitudes north and south of these; its period is 9h 55 m 40.6s. System III
37625-408: The polar regions of Jupiter. As a result, radio waves are generated through a cyclotron maser mechanism , and the energy is transmitted out along a cone-shaped surface. When Earth intersects this cone, the radio emissions from Jupiter can exceed the radio output of the Sun. Jupiter has a faint planetary ring system composed of three main segments: an inner torus of particles known as the halo,
37840-426: The positions of the planets. These schemes, which were based on geometry rather than the arithmetic of the Babylonians, would eventually eclipse the Babylonians' theories in complexity and comprehensiveness and account for most of the astronomical movements observed from Earth with the naked eye. These theories would reach their fullest expression in the Almagest written by Ptolemy in the 2nd century CE. So complete
38055-456: The presence of a third or more giant planets tends to induce larger eccentricities. The axial tilt of Jupiter is 3.13°, which is relatively small, so its seasons are insignificant compared to those of Earth and Mars. Jupiter's rotation is the fastest of all the Solar System's planets, completing a rotation on its axis in slightly less than ten hours; this creates an equatorial bulge easily seen through an amateur telescope. Because Jupiter
38270-409: The radius of the Sun, and its mass is one thousandth the mass of the Sun , as the densities of the two bodies are similar. A " Jupiter mass " ( M J or M Jup ) is used as a unit to describe masses of other objects, particularly extrasolar planets and brown dwarfs . For example, the extrasolar planet HD 209458 b has a mass of 0.69 M J , while the brown dwarf Gliese 229 b has
38485-424: The request of Apollo's mother, Leto , Zeus instead ordered Apollo to serve as a slave to King Admetus of Pherae for a year. According to Diodorus Siculus , Zeus killed Asclepius because of complains from Hades, who was worried that the number of people in the underworld was diminishing because of Asclepius's resurrections. The winged horse Pegasus carried the thunderbolts of Zeus. Zeus took pity on Ixion ,
38700-476: The ring system is unknown, possibly dating back to Jupiter's formation. At least 95 moons orbit the planet; the four largest moons — Io , Europa , Ganymede , and Callisto —orbit within the magnetosphere, and were discovered by Galileo Galilei in 1610. Ganymede, the largest of the four, is larger than the planet Mercury . Since 1973, Jupiter has been visited by nine robotic probes : seven flybys and two dedicated orbiters, with two more en route. In both
38915-712: The same ( Aphrodite , Greek corresponding to Latin Venus ), though this had long been known in Mesopotamia. In the 3rd century BC, Aristarchus of Samos proposed a heliocentric system, according to which Earth and the planets revolved around the Sun. The geocentric system remained dominant until the Scientific Revolution . By the 1st century BC, during the Hellenistic period , the Greeks had begun to develop their own mathematical schemes for predicting
39130-556: The same way as terrestrial thunderstorms, driven by the heat rising from the interior. The Juno mission revealed the presence of "shallow lightning" which originates from ammonia-water clouds relatively high in the atmosphere. These discharges carry "mushballs" of water-ammonia slushes covered in ice, which fall deep into the atmosphere. Upper-atmospheric lightning has been observed in Jupiter's upper atmosphere, bright flashes of light that last around 1.4 milliseconds. These are known as "elves" or "sprites" and appear blue or pink due to
39345-469: The second millennium BC. The MUL.APIN is a pair of cuneiform tablets dating from the 7th century BC that lays out the motions of the Sun, Moon, and planets over the course of the year. Late Babylonian astronomy is the origin of Western astronomy and indeed all Western efforts in the exact sciences . The Enuma anu enlil , written during the Neo-Assyrian period in the 7th century BC, comprises
39560-433: The sheet co-rotates with the planet, causing deformation of the dipole magnetic field into that of a magnetodisk. Electrons within the plasma sheet generate a strong radio signature, with short, superimposed bursts in the range of 0.6–30 MHz that are detectable from Earth with consumer-grade shortwave radio receivers . As Io moves through this torus, the interaction generates Alfvén waves that carry ionized matter into
39775-433: The short term, it has maintained its general position in the atmosphere for more than 15 years. It may be a giant vortex similar to the Great Red Spot, and appears to be quasi-stable like the vortices in Earth's thermosphere. This feature may be formed by interactions between charged particles generated from Io and the strong magnetic field of Jupiter, resulting in a redistribution of heat flow. Jupiter's magnetic field
39990-421: The size of Neptune and smaller, down to smaller than Mercury. In 2011, the Kepler space telescope team reported the discovery of the first Earth-sized exoplanets orbiting a Sun-like star , Kepler-20e and Kepler-20f . Since that time, more than 100 planets have been identified that are approximately the same size as Earth , 20 of which orbit in the habitable zone of their star—the range of orbits where
40205-506: The size of the Moon . Analysis of gravitational microlensing data suggests a minimum average of 1.6 bound planets for every star in the Milky Way . In early 1992, radio astronomers Aleksander Wolszczan and Dale Frail announced the discovery of two planets orbiting the pulsar PSR 1257+12 . This discovery was confirmed and is generally considered to be the first definitive detection of exoplanets. Researchers suspect they formed from
40420-413: The smaller planetesimals (as well as radioactive decay ) will heat up the growing planet, causing it to at least partially melt. The interior of the planet begins to differentiate by density, with higher density materials sinking toward the core . Smaller terrestrial planets lose most of their atmospheres because of this accretion, but the lost gases can be replaced by outgassing from the mantle and from
40635-488: The son born of Thetis would be mightier than his father, Thetis was married off to the mortal Peleus . Zeus was afraid that his grandson Asclepius would teach resurrection to humans, so he killed Asclepius with his thunderbolt. This angered Asclepius's father, Apollo , who in turn killed the Cyclopes who had fashioned the thunderbolts of Zeus. Angered at this, Zeus would have imprisoned Apollo in Tartarus. However, at
40850-470: The spin axis of the planet. There is great variation in the length of day between the planets, with Venus taking 243 days to rotate, and the giant planets only a few hours. The rotational periods of exoplanets are not known, but for hot Jupiters , their proximity to their stars means that they are tidally locked (that is, their orbits are in sync with their rotations). This means, they always show one face to their stars, with one side in perpetual day,
41065-400: The star is called its apastron ( aphelion ). As a planet approaches periastron, its speed increases as it trades gravitational potential energy for kinetic energy , just as a falling object on Earth accelerates as it falls. As the planet nears apastron, its speed decreases, just as an object thrown upwards on Earth slows down as it reaches the apex of its trajectory . Each planet's orbit
41280-523: The star or each other, but over time many will collide, either to form a larger, combined protoplanet or release material for other protoplanets to absorb. Those objects that have become massive enough will capture most matter in their orbital neighbourhoods to become planets. Protoplanets that have avoided collisions may become natural satellites of planets through a process of gravitational capture, or remain in belts of other objects to become either dwarf planets or small bodies . The energetic impacts of
41495-504: The stars. He also theorized that the orbits of planets were elliptical . Aryabhata's followers were particularly strong in South India , where his principles of the diurnal rotation of Earth, among others, were followed and a number of secondary works were based on them. Zeus Zeus ( / zj uː s / , Ancient Greek : Ζεύς ) is the sky and thunder god in ancient Greek religion and mythology , who rules as king of
41710-460: The subsequent impact of comets (smaller planets will lose any atmosphere they gain through various escape mechanisms ). With the discovery and observation of planetary systems around stars other than the Sun, it is becoming possible to elaborate, revise or even replace this account. The level of metallicity —an astronomical term describing the abundance of chemical elements with an atomic number greater than 2 ( helium )—appears to determine
41925-412: The super-Earth Gliese 1214 b , and others. Hot Jupiters, due to their extreme proximities to their host stars, have been shown to be losing their atmospheres into space due to stellar radiation, much like the tails of comets. These planets may have vast differences in temperature between their day and night sides that produce supersonic winds, although multiple factors are involved and the details of
42140-430: The surrounding cloud tops. The Spot's composition and the source of its red colour remain uncertain, although photodissociated ammonia reacting with acetylene is a likely explanation. The Great Red Spot is larger than the Earth. Mathematical models suggest that the storm is stable and will be a permanent feature of the planet. However, it has significantly decreased in size since its discovery. Initial observations in
42355-550: The term planet more broadly, including dwarf planets as well as rounded satellites like the Moon. Further advances in astronomy led to the discovery of over five thousand planets outside the Solar System, termed exoplanets . These often show unusual features that the Solar System planets do not show, such as hot Jupiters —giant planets that orbit close to their parent stars, like 51 Pegasi b —and extremely eccentric orbits , such as HD 20782 b . The discovery of brown dwarfs and planets larger than Jupiter also spurred debate on
42570-433: The terrestrial planets in composition. The gas giants , Jupiter and Saturn, are primarily composed of hydrogen and helium and are the most massive planets in the Solar System. Saturn is one third as massive as Jupiter, at 95 Earth masses. The ice giants , Uranus and Neptune, are primarily composed of low-boiling-point materials such as water, methane , and ammonia , with thick atmospheres of hydrogen and helium. They have
42785-505: The threat, in the form of the potential mother, and so the "cycle of displacement" is brought to an end. In addition, the myth can be seen as an allegory for Zeus gaining the wisdom of Metis for himself by swallowing her. In Hesiod's account, Zeus's second wife is Themis , one of the Titan daughters of Uranus and Gaia, with whom he has the Horae , listed as Eunomia , Dike and Eirene , and
43000-609: The three Moirai : Clotho , Lachesis and Atropos . A fragment from Pindar calls Themis Zeus's first wife, and states that she is brought by the Moirai (in this version not her daughters) up to Olympus, where she becomes the bride of Zeus and bears him the Horae. According to Hesiod, Zeus next marries the Oceanid Eurynome , with whom he has the three Charites , namely Aglaea , Euphrosyne and Thalia . Zeus's fourth wife
43215-494: The time of its formation, Jupiter was hotter and was about twice its current diameter. Before the early 21st century, most scientists proposed one of two scenarios for the formation of Jupiter. If the planet accreted first as a solid body, it would consist of a dense core , a surrounding layer of fluid metallic hydrogen (with some helium) extending outward to about 80% of the radius of the planet, and an outer atmosphere consisting primarily of molecular hydrogen . Alternatively, if
43430-468: The two distinct components of the dusty gossamer ring. There is evidence of a fourth ring that may consist of collisional debris from Amalthea that is strung along the same moon's orbit. Jupiter is the only planet whose barycentre with the Sun lies outside the volume of the Sun, though by 7% of the Sun's radius. The average distance between Jupiter and the Sun is 778 million km ( 5.2 AU ) and it completes an orbit every 11.86 years. This
43645-511: The two of them meet in a cataclysmic battle, before Zeus defeats him easily with his thunderbolt, and the creature is hurled down to Tartarus. Epimenides presents a different version, in which Typhon makes his way into Zeus's palace while he is sleeping, only for Zeus to wake and kill the monster with a thunderbolt. Aeschylus and Pindar give somewhat similar accounts to Hesiod, in that Zeus overcomes Typhon with relative ease, defeating him with his thunderbolt. Apollodorus, in contrast, provides
43860-530: The wife of Amphitryon , in the form of her own husband. Several accounts state that Zeus approached the Argive princess Danae in the form of a shower of gold, and according to Ovid he abducts Aegina in the form of a flame. In accounts of Zeus's affairs, Hera is often depicted as a jealous wife, with there being various stories of her persecuting either the women with whom Zeus sleeps, or their children by him. Several authors relate that Zeus sleeps with Io ,
44075-558: The world from further harm. In a satirical work, Dialogues of the Gods by Lucian , Zeus berates Helios for allowing such thing to happen; he returns the damaged chariot to him and warns him that if he dares do that again, he will strike him with one of this thunderbolts. Zeus played a dominant role, presiding over the Greek Olympian pantheon. He fathered many of the heroes and was featured in many of their local cults . Though
44290-504: Was achieved. Although Jupiter would need to be about 75 times more massive to fuse hydrogen and become a star , its diameter is sufficient as the smallest red dwarf may be slightly larger in radius than Saturn. Jupiter radiates more heat than it receives through solar radiation, due to the Kelvin–Helmholtz mechanism within its contracting interior. This process causes Jupiter to shrink by about 1 mm (0.039 in) per year. At
44505-411: Was also called Zen, because the humans believed that he was the cause of life (zen). While Lactantius wrote that he was called Zeus and Zen, not because he is the giver of life, but because he was the first who lived of the children of Cronus . Zeus was called by numerous alternative names or surnames, known as epithets . Some epithets are the surviving names of local gods who were consolidated into
44720-521: Was born in a cave in Dicte. While the Theogony says nothing of Zeus's upbringing other than that he grew up swiftly, other sources provide more detailed accounts. According to Apollodorus, Rhea, after giving birth to Zeus in a cave in Dicte, gives him to the nymphs Adrasteia and Ida , daughters of Melisseus , to nurse. They feed him on the milk of the she-goat Amalthea , while the Kouretes guard
44935-479: Was defined by radio astronomers and corresponds to the rotation of the planet's magnetosphere; its period is Jupiter's official rotation. Jupiter is usually the fourth brightest object in the sky (after the Sun, the Moon , and Venus ), although at opposition Mars can appear brighter than Jupiter. Depending on Jupiter's position with respect to the Earth, it can vary in visual magnitude from as bright as −2.94 at opposition down to −1.66 during conjunction with
45150-413: Was derived. In ancient Greece , China , Babylon , and indeed all pre-modern civilizations, it was almost universally believed that Earth was the center of the Universe and that all the "planets" circled Earth. The reasons for this perception were that stars and planets appeared to revolve around Earth each day and the apparently common-sense perceptions that Earth was solid and stable and that it
45365-416: Was found in 1992 in orbit around a pulsar . Its mass is roughly half that of the planet Mercury. Even smaller is WD 1145+017 b , orbiting a white dwarf; its mass is roughly that of the dwarf planet Haumea, and it is typically termed a minor planet. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b , with a mass (and radius) that is probably slightly higher than that of
45580-589: Was not moving but at rest. The first civilization known to have a functional theory of the planets were the Babylonians , who lived in Mesopotamia in the first and second millennia BC. The oldest surviving planetary astronomical text is the Babylonian Venus tablet of Ammisaduqa , a 7th-century BC copy of a list of observations of the motions of the planet Venus, that probably dates as early as
45795-402: Was raised, and Zeus, unable to resolve the situation, seeks the advice of Cithaeron, ruler of Plataea , supposedly the most intelligent man on earth. Cithaeron instructs him to fashion a wooden statue and dress it as a bride, and then pretend that he is marrying one "Plataea", a daughter of Asopus . When Hera hears of this, she immediately rushes there, only to discover the ruse upon ripping away
46010-518: Was the domination of Ptolemy's model that it superseded all previous works on astronomy and remained the definitive astronomical text in the Western world for 13 centuries. To the Greeks and Romans, there were seven known planets, each presumed to be circling Earth according to the complex laws laid out by Ptolemy. They were, in increasing order from Earth (in Ptolemy's order and using modern names):
46225-462: Was the result of a runaway greenhouse effect in its history, which today makes it the hottest planet by surface temperature, hotter even than Mercury. Despite hostile surface conditions, temperature, and pressure at about 50–55 km altitude in Venus's atmosphere are close to Earthlike conditions (the only place in the Solar System beyond Earth where this is so), and this region has been suggested as
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