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116-476: By 2011 there were 180 known super-Jupiters, some hot , some cold. Even though they are more massive than Jupiter, they remain about the same size as Jupiter up to 80 Jupiter masses. This means that their surface gravity and density go up proportionally to their mass. The increased mass compresses the planet due to gravity , thus keeping it from being larger. In comparison, planets somewhat lighter than Jupiter can be larger, so-called " puffy planets " (gas giants with

232-462: A white dwarf . In the distant future, the gravity of passing stars will gradually reduce the Sun's retinue of planets. Some planets will be destroyed, and others ejected into interstellar space . Ultimately, over the course of tens of billions of years, it is likely that the Sun will be left with none of the original bodies in orbit around it. Ideas concerning the origin and fate of the world date from

348-532: A class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods ( P < 10 days ). The close proximity to their stars and high surface-atmosphere temperatures resulted in their informal name "hot Jupiters". Hot Jupiters are the easiest extrasolar planets to detect via the radial-velocity method, because the oscillations they induce in their parent stars' motion are relatively large and rapid compared to those of other known types of planets. One of

464-527: A dayside temperature greater than 2,200 K (1,930 °C; 3,500 °F). In such dayside atmospheres, most molecules dissociate into their constituent atoms and circulate to the nightside where they recombine into molecules again. One example is TOI-1431b , announced by the University of Southern Queensland in April 2021, which has an orbital period of just two and a half days. Its dayside temperature

580-470: A diameter of about 200 AU and form a hot, dense protostar (a star in which hydrogen fusion has not yet begun) at the centre. Since about half of all known stars form systems of multiple stars and because 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 a protostar system with Jupiter being

696-528: A different team found that every time they observe the exoplanet at a certain position in its orbit, they also detected X-ray flares. In 2019, astronomers analyzed data from Arecibo Observatory , MOST , and the Automated Photoelectric Telescope, in addition to historical observations of the star at radio, optical, ultraviolet, and X-ray wavelengths to examine these claims. They found that the previous claims were exaggerated and

812-423: A disk of gas and dust. Pressure partially supported the gas and so did not orbit the Sun as rapidly as the planets. The resulting drag and, more importantly, gravitational interactions with the surrounding material caused a transfer of angular momentum , and as a result the planets gradually migrated to new orbits. Models show that density and temperature variations in the disk governed this rate of migration, but

928-557: A few million years after Jupiter, when there was less gas available to consume. T Tauri stars like the young Sun have far stronger stellar winds than more stable, older stars. Uranus and Neptune are thought to have formed after Jupiter and Saturn did, when the strong solar wind had blown away much of the disc material. As a result, those planets accumulated little hydrogen and helium—not more than 1  M E each. Uranus and Neptune are sometimes referred to as failed cores. The main problem with formation theories for these planets

1044-442: A hot Jupiter's passage would be particularly water-rich. According to a 2011 study, hot Jupiters may become disrupted planets while migrating inwards; this could explain an abundance of "hot" Earth-sized to Neptune-sized planets within 0.2 AU of their host star. One example of these sorts of systems is that of WASP-47 . There are three inner planets and an outer gas giant in the habitable zone. The innermost planet, WASP-47e,

1160-402: A large diameter but low density). An example of this may be the exoplanet HAT-P-1b with about half the mass of Jupiter but about 1.38 times larger diameter. CoRoT-3b , with a mass around 22 Jupiter masses, is predicted to have an average density of 26.4 g/cm, greater than osmium (22.6 g/cm), the densest natural element under standard conditions. Extreme compression of matter inside it causes

1276-533: A large radius and very low density are sometimes called "puffy planets" or "hot Saturns", due to their density being similar to Saturn 's. Puffy planets orbit close to their stars so that the intense heat from the star combined with internal heating within the planet will help inflate the atmosphere . Six large-radius low-density planets have been detected by the transit method . In order of discovery they are: HAT-P-1b , CoRoT-1b , TrES-4b , WASP-12b , WASP-17b , and Kepler-7b . Some hot Jupiters detected by

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1392-588: A number of ways, most notably the possibility of accreting material from the stellar winds of their stars and, assuming a fast rotation (not tidally locked to their stars), a much more evenly distributed heat with many narrow-banded jets. Their detection using the transit method would be much more difficult due to their tiny size compared to the stars they orbit, as well as the long time needed (months or even years) for one to transit their star as well as to be occulted by it. Theoretical research since 2000 suggested that "hot Jupiters" may cause increased flaring due to

1508-422: A planet along its orbit ultimately becomes impossible to predict with any certainty (so, for example, the timing of winter and summer becomes uncertain). Still, in some cases, the orbits themselves may change dramatically. Such chaos manifests most strongly as changes in eccentricity , with some planets' orbits becoming significantly more—or less— elliptical . Ultimately, the Solar System is stable in that none of

1624-565: A quarter light-years ) across. The further collapse of the fragments led to the formation of dense cores 0.01–0.1 parsec (2,000–20,000  AU ) in size. One of these collapsing fragments (known as the presolar nebula ) formed what became the Solar System. The composition of this region with a mass just over that of the Sun ( M ☉ ) was about the same as that of the Sun today, with hydrogen , along with helium and trace amounts of lithium produced by Big Bang nucleosynthesis , forming about 98% of its mass. The remaining 2% of

1740-425: A red giant finally casts off its outer layers, these elements would then be recycled to form other star systems. The nebular hypothesis says that the Solar System formed from the gravitational collapse of a fragment of a giant molecular cloud , most likely at the edge of a Wolf-Rayet bubble . The cloud was about 20  parsecs (65 light years) across, while the fragments were roughly 1 parsec (three and

1856-490: A role in the final accretion of the terrestrial planets. During this primary depletion period, the effects of the giant planets and planetary embryos left the asteroid belt with a total mass equivalent to less than 1% that of the Earth, composed mainly of small planetesimals. This is still 10–20 times more than the current mass in the main belt, which is now about 0.0005  M E . A secondary depletion period that brought

1972-454: A substantially larger fraction of the planet's mass. No such objects have been found yet and they are still hypothetical. Simulations have shown that the migration of a Jupiter-sized planet through the inner protoplanetary disk (the region between 5 and 0.1 AU from the star) is not as destructive as expected. More than 60% of the solid disk materials in that region are scattered outward, including planetesimals and protoplanets , allowing

2088-527: Is chaotic over million- and billion-year timescales, with the orbits of the planets open to long-term variations. One notable example of this chaos is the Neptune–Pluto system, which lies in a 3:2 orbital resonance . Although the resonance itself will remain stable, it becomes impossible to predict the position of Pluto with any degree of accuracy more than 10–20 million years (the Lyapunov time ) into

2204-504: Is 2,700 K (2,430 °C; 4,400 °F), making it hotter than 40% of stars in our galaxy. The nightside temperature is 2,600 K (2,330 °C; 4,220 °F). Ultra-short period planets (USP) are a class of planets with orbital periods below one day and occur only around stars of less than about 1.25 solar masses . Confirmed transiting hot Jupiters that have orbital periods of less than one day include WASP-18b , Banksia , Astrolábos , and WASP-103b . Gas giants with

2320-581: Is a large terrestrial planet of 6.83 Earth masses and 1.8 Earth radii; the hot Jupiter, b, is little heavier than Jupiter, but about 12.63 Earth radii; a final hot Neptune, c, is 15.2 Earth masses and 3.6 Earth radii. A similar orbital architecture is also exhibited by the Kepler-30 system. Several hot Jupiters, such as HD 80606 b , have orbits that are misaligned with their host stars, including several with retrograde orbits such as HAT-P-14b . This misalignment may be related to

2436-404: Is no accident that Jupiter lies just beyond the frost line. Because the frost line accumulated large amounts of water via evaporation from infalling icy material, it created a region of lower pressure that increased the speed of orbiting dust particles and halted their motion toward the Sun. In effect, the frost line acted as a barrier that caused the material to accumulate rapidly at ~5 AU from

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2552-411: Is no longer believed to have a "star-planet interaction." Some researchers had also suggested that HD 189733 accretes, or pulls, material from its orbiting exoplanet at a rate similar to those found around young protostars in T Tauri star systems . Later analysis demonstrated that very little, if any, gas was accreted from the "hot Jupiter" companion. Solar nebula There is evidence that

2668-454: Is not complete, and may still pose a threat to life on Earth. Over the course of the Solar System's evolution, comets were ejected out of the inner Solar System by the gravity of the giant planets and sent thousands of AU outward to form the Oort cloud , a spherical outer swarm of cometary nuclei at the farthest extent of the Sun's gravitational pull. Eventually, after about 800 million years,

2784-434: Is not widely accepted. According to the nebular hypothesis, the outer two planets may be in the "wrong place". Uranus and Neptune (known as the " ice giants ") exist in a region where the reduced density of the solar nebula and longer orbital times render their formation there highly implausible. The two are instead thought to have formed in orbits near Jupiter and Saturn (known as the " gas giants "), where more material

2900-641: Is orbited by at least 1 large exomoon . It has been proposed that gas giants orbiting red giants at distances similar to that of Jupiter could be hot Jupiters due to the intense irradiation they would receive from their stars. It is very likely that in the Solar System Jupiter will become a hot Jupiter after the transformation of the Sun into a red giant. The recent discovery of particularly low density gas giants orbiting red giant stars supports this hypothesis. Hot Jupiters orbiting red giants would differ from those orbiting main-sequence stars in

3016-405: Is that terrestrials formed in a disc of gas still not expelled by the Sun. The " gravitational drag " of this residual gas would have eventually lowered the planets' energy, smoothing out their orbits. However, such gas, if it existed, would have prevented the terrestrial planets' orbits from becoming so eccentric in the first place. Another hypothesis is that gravitational drag occurred not between

3132-571: Is the timescale of their formation. At the current locations it would have taken millions of years for their cores to accrete. This means that Uranus and Neptune may have formed closer to the Sun—near or even between Jupiter and Saturn—later migrating or being ejected outward (see Planetary migration below). Motion in the planetesimal era was not all inward toward the Sun; the Stardust sample return from Comet Wild 2 has suggested that materials from

3248-496: Is thought to have formed as a result of a single, large head-on collision . The impacting object probably had a mass comparable to that of Mars, and the impact probably occurred near the end of the period of giant impacts. The collision kicked into orbit some of the impactor's mantle, which then coalesced into the Moon. The impact was probably the last in a series of mergers that formed the Earth. It has been further hypothesized that

3364-434: Is thought to have formed the Moon (see Moons below), while another removed the outer envelope of the young Mercury . One unresolved issue with this model is that it cannot explain how the initial orbits of the proto-terrestrial planets, which would have needed to be highly eccentric in order to collide, produced the remarkably stable and nearly circular orbits they have today. One hypothesis for this "eccentricity dumping"

3480-476: The Cassini–Huygens spacecraft suggests they formed relatively late. In the long term, the greatest changes in the Solar System will come from changes in the Sun itself as it ages. As the Sun burns through its hydrogen fuel supply, it gets hotter and burns the remaining fuel even faster. As a result, the Sun is growing brighter at a rate of ten percent every 1.1 billion years. In about 600 million years,

3596-466: The Grand tack hypothesis ), proposes that Jupiter had migrated inward to 1.5 AU. After Saturn formed, migrated inward, and established the 2:3 mean motion resonance with Jupiter, the study assumes that both planets migrated back to their present positions. Jupiter thus would have consumed much of the material that would have created a bigger Mars. The same simulations also reproduce the characteristics of

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3712-477: The Nice model , after the formation of the Solar System, the orbits of all the giant planets continued to change slowly, influenced by their interaction with the large number of remaining planetesimals. After 500–600 million years (about 4 billion years ago) Jupiter and Saturn fell into a 2:1 resonance: Saturn orbited the Sun once for every two Jupiter orbits. This resonance created a gravitational push against

3828-578: The Orion Nebula . Studies of the structure of the Kuiper belt and of anomalous materials within it suggest that the Sun formed within a cluster of between 1,000 and 10,000 stars with a diameter of between 6.5 and 19.5 light years and a collective mass of 3,000  M ☉ . This cluster began to break apart between 135 million and 535 million years after formation. Several simulations of our young Sun interacting with close-passing stars over

3944-423: The frost line , from rock, ice, and gases via the core accretion method of planetary formation . The planet then migrates inwards to the star where it eventually forms a stable orbit. The planet may have migrated inward smoothly via type II orbital migration. Or it may have migrated more suddenly due to gravitational scattering onto eccentric orbits during an encounter with another massive planet, followed by

4060-406: The radial-velocity method may be puffy planets. Most of these planets are around or below Jupiter mass as more massive planets have stronger gravity keeping them at roughly Jupiter's size. Indeed, hot Jupiters with masses below Jupiter, and temperatures above 1800 Kelvin, are so inflated and puffed out that they are all on unstable evolutionary paths which eventually lead to Roche-Lobe overflow and

4176-630: The terrestrial planets ( Mercury , Venus , Earth , and Mars ). These compounds are quite rare in the Universe, comprising only 0.6% of the mass of the nebula, so the terrestrial planets could not grow very large. The terrestrial embryos grew to about 0.05 Earth masses ( M E ) and ceased accumulating matter about 100,000 years after the formation of the Sun; subsequent collisions and mergers between these planet-sized bodies allowed terrestrial planets to grow to their present sizes. When terrestrial planets were forming, they remained immersed in

4292-403: The 18th century. The most significant criticism of the hypothesis was its apparent inability to explain the Sun's relative lack of angular momentum when compared to the planets. However, since the early 1980s studies of young stars have shown them to be surrounded by cool discs of dust and gas, exactly as the nebular hypothesis predicts, which has led to its re-acceptance. Understanding of how

4408-438: The Earth's surface too hot for liquid water to exist there naturally. At this point, all life will be reduced to single-celled organisms. Evaporation of water, a potent greenhouse gas , from the oceans' surface could accelerate temperature increase, potentially ending all life on Earth even sooner. During this time, it is possible that as Mars 's surface temperature gradually rises, carbon dioxide and water currently frozen under

4524-458: The Kuiper belt was much denser and closer to the Sun, with an outer edge at approximately 30 AU. Its inner edge would have been just beyond the orbits of Uranus and Neptune, which were in turn far closer to the Sun when they formed (most likely in the range of 15–20 AU), and in 50% of simulations ended up in opposite locations, with Uranus farther from the Sun than Neptune. According to

4640-533: The Mars-sized object may have formed at one of the stable Earth–Sun Lagrangian points (either L 4 or L 5 ) and drifted from its position. The moons of trans-Neptunian objects Pluto ( Charon ) and Orcus ( Vanth ) may also have formed by means of a large collision: the Pluto–Charon, Orcus–Vanth and Earth–Moon systems are unusual in the Solar System in that the satellite's mass is at least 1% that of

4756-460: The Moon is tidally locked to the Earth; one of its revolutions around the Earth (currently about 29 days) is equal to one of its rotations about its axis, so it always shows one face to the Earth. The Moon will continue to recede from Earth, and Earth's spin will continue to slow gradually. Other examples are the Galilean moons of Jupiter (as well as many of Jupiter's smaller moons) and most of

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4872-474: The Orion Nebula —and are rather cool, reaching a surface temperature of only about 1,000 K (730 °C; 1,340 °F) at their hottest. Within 50 million years, the temperature and pressure at the core of the Sun became so great that its hydrogen began to fuse, creating an internal source of energy that countered gravitational contraction until hydrostatic equilibrium was achieved. This marked

4988-400: The Solar System altogether or send it on a collision course with Venus or Earth . This could happen within a billion years, according to numerical simulations in which Mercury's orbit is perturbed. The evolution of moon systems is driven by tidal forces . A moon will raise a tidal bulge in the object it orbits (the primary) due to the differential gravitational force across diameter of

5104-492: The Solar System. The water was probably delivered by planetary embryos and small planetesimals thrown out of the asteroid belt by Jupiter. A population of main-belt comets discovered in 2006 has also been suggested as a possible source for Earth's water. In contrast, comets from the Kuiper belt or farther regions delivered not more than about 6% of Earth's water. The panspermia hypothesis holds that life itself may have been deposited on Earth in this way, although this idea

5220-574: The Solar System. This caused Jupiter to move slightly inward. Those objects scattered by Jupiter into highly elliptical orbits formed the Oort cloud; those objects scattered to a lesser degree by the migrating Neptune formed the current Kuiper belt and scattered disc. This scenario explains the Kuiper belt's and scattered disc's present low mass. Some of the scattered objects, including Pluto , became gravitationally tied to Neptune's orbit, forcing them into mean-motion resonances . Eventually, friction within

5336-475: The Sun by creating relatively dense regions within the cloud, causing these regions to collapse. The highly homogeneous distribution of iron-60 in the Solar System points to the occurrence of this supernova and its injection of iron-60 being well before the accretion of nebular dust into planetary bodies. Because only massive, short-lived stars produce supernovae, the Sun must have formed in a large star-forming region that produced massive stars, possibly similar to

5452-576: The Sun is expected to continue to evolve required an understanding of the source of its power. Arthur Stanley Eddington 's confirmation of Albert Einstein 's theory of relativity led to his realisation that the Sun's energy comes from nuclear fusion reactions in its core, fusing hydrogen into helium. In 1935, Eddington went further and suggested that other elements also might form within stars. Fred Hoyle elaborated on this premise by arguing that evolved stars called red giants created many elements heavier than hydrogen and helium in their cores. When

5568-417: The Sun's brightness will have disrupted the Earth's carbon cycle to the point where trees and forests (C3 photosynthetic plant life) will no longer be able to survive; and in around 800 million years, the Sun will have killed all complex life on the Earth's surface and in the oceans. In 1.1 billion years, the Sun's increased radiation output will cause its circumstellar habitable zone to move outwards, making

5684-511: The Sun's entry into the prime phase of its life, known as the main sequence . Main-sequence stars derive energy from the fusion of hydrogen into helium in their cores. The Sun remains a main-sequence star today. As the early Solar System continued to evolve, it eventually drifted away from its siblings in the stellar nursery, and continued orbiting the Milky Way 's center on its own. The Sun likely drifted from its original orbital distance from

5800-532: The Sun, the region's history changed dramatically. Orbital resonances with Jupiter and Saturn are particularly strong in the asteroid belt, and gravitational interactions with more massive embryos scattered many planetesimals into those resonances. Jupiter's gravity increased the velocity of objects within these resonances, causing them to shatter upon collision with other bodies, rather than accrete. As Jupiter migrated inward following its formation (see Planetary migration below), resonances would have swept across

5916-498: The Sun. This excess material coalesced into a large embryo (or core) on the order of 10  M E , which began to accumulate an envelope via accretion of gas from the surrounding disc at an ever-increasing rate. Once the envelope mass became about equal to the solid core mass, growth proceeded very rapidly, reaching about 150 Earth masses ~10  years thereafter and finally topping out at 318  M E . Saturn may owe its substantially lower mass simply to having formed

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6032-457: The asteroid belt down close to its present mass is thought to have followed when Jupiter and Saturn entered a temporary 2:1 orbital resonance (see below). The inner Solar System's period of giant impacts probably played a role in Earth acquiring its current water content (~6 × 10  kg) from the early asteroid belt. Water is too volatile to have been present at Earth's formation and must have been subsequently delivered from outer, colder parts of

6148-430: The asteroid belt, dynamically exciting the region's population and increasing their velocities relative to each other. The cumulative action of the resonances and the embryos either scattered the planetesimals away from the asteroid belt or excited their orbital inclinations and eccentricities . Some of those massive embryos too were ejected by Jupiter, while others may have migrated to the inner Solar System and played

6264-420: The atmospheric ionization, and thus the greater the magnitude of the interaction and the larger the electric current, leading to more heating and expansion of the planet. This theory matches the observation that planetary temperature is correlated with inflated planetary radii. Theoretical research suggests that hot Jupiters are unlikely to have moons , due to both a small Hill sphere and the tidal forces of

6380-421: The best-known hot Jupiters is 51 Pegasi b . Discovered in 1995, it was the first extrasolar planet found orbiting a Sun-like star . 51 Pegasi b has an orbital period of about 4 days. Though there is diversity among hot Jupiters, they do share some common properties. There are three schools of thought regarding the possible origin of hot Jupiters. One possibility is that they were formed in-situ at

6496-422: The center of the galaxy. The chemical history of the Sun suggests it may have formed as much as 3 kpc closer to the galaxy core. Like most stars, the Sun likely formed not in isolation but as part of a young star cluster . There are several indications that hint at the cluster environment having had some influence over the young, still-forming solar system. For example, the decline in mass beyond Neptune and

6612-564: The centre of the system and the Earth in orbit around it. This concept had been developed for millennia ( Aristarchus of Samos had suggested it as early as 250 BC), but was not widely accepted until the end of the 17th century. The first recorded use of the term "Solar System" dates from 1704. The current standard theory for Solar System formation, the nebular hypothesis , has fallen into and out of favour since its formulation by Emanuel Swedenborg , Immanuel Kant , and Pierre-Simon Laplace in

6728-439: The characteristics expected of captured bodies. Most such moons orbit in the direction opposite to the rotation of their primary. The largest irregular moon is Neptune's moon Triton , which is thought to be a captured Kuiper belt object . Moons of solid Solar System bodies have been created by both collisions and capture. Mars 's two small moons, Deimos and Phobos , are thought to be captured asteroids . The Earth's moon

6844-565: The circularization and shrinking of the orbits due to tidal interactions with the star. A hot Jupiter's orbit could also have been altered via the Kozai mechanism , causing an exchange of inclination for eccentricity resulting in a high eccentricity low perihelion orbit, in combination with tidal friction. This requires a massive body—another planet or a stellar companion —on a more distant and inclined orbit; approximately 50% of hot Jupiters have distant Jupiter-mass or larger companions, which can leave

6960-486: The cores of the hot Jupiters began as more common super-Earths which accreted their gas envelopes at their current locations, becoming gas giants in situ . The super-Earths providing the cores in this hypothesis could have formed either in situ or at greater distances and have undergone migration before acquiring their gas envelopes. Since super-Earths are often found with companions, the hot Jupiters formed in situ could also be expected to have companions. The increase of

7076-452: The cosmo-chemical constraints indicates that there was likely no late spike (“terminal cataclysm”) in the bombardment rate. If it occurred, this period of heavy bombardment lasted several hundred million years and is evident in the cratering still visible on geologically dead bodies of the inner Solar System such as the Moon and Mercury. The oldest known evidence for life on Earth dates to 3.8 billion years ago—almost immediately after

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7192-422: The distances at which they are currently observed. Another possibility is that they were formed at a distance but later migrated inward. Such a shift in position might occur due to interactions with gas and dust during the solar nebula phase. It might also occur as a result of a close encounter with another large object destabilizing a Jupiter's orbit. In the migration hypothesis, a hot Jupiter forms beyond

7308-400: The earliest known writings; however, for almost all of that time, there was no attempt to link such theories to the existence of a "Solar System", simply because it was not generally thought that the Solar System, in the sense we now understand it, existed. The first step toward a theory of Solar System formation and evolution was the general acceptance of heliocentrism , which placed the Sun at

7424-459: The early formation of the Solar System migrated from the warmer inner Solar System to the region of the Kuiper belt. After between three and ten million years, the young Sun's solar wind would have cleared away all the gas and dust in the protoplanetary disc, blowing it into interstellar space, thus ending the growth of the planets. The planets were originally thought to have formed in or near their current orbits. This has been questioned during

7540-675: The end of the Late Heavy Bombardment. Impacts are thought to be a regular (if currently infrequent) part of the evolution of the Solar System. That they continue to happen is evidenced by the collision of Comet Shoemaker–Levy 9 with Jupiter in 1994, the 2009 Jupiter impact event , the Tunguska event , the Chelyabinsk meteor and the impact that created Meteor Crater in Arizona . The process of accretion, therefore,

7656-407: The evaporation and loss of the planet's atmosphere. Even when taking surface heating from the star into account, many transiting hot Jupiters have a larger radius than expected. This could be caused by the interaction between atmospheric winds and the planet's magnetosphere creating an electric current through the planet that heats it up , causing it to expand. The hotter the planet, the greater

7772-410: The extreme eccentric-orbit of Sedna have been interpreted as a signature of the solar system having been influenced by its birth environment. Whether the presence of the isotopes iron-60 and aluminium-26 can be interpreted as a sign of a birth cluster containing massive stars is still under debate. If the Sun was part of a star cluster, it might have been influenced by close flybys of other stars,

7888-471: The first 100 million years of its life produced anomalous orbits observed in the outer Solar System, such as detached objects . A recent study suggests that such a passing star is not only responsible for the orbits of the detached objects but also the hot and cold Kuiper belt population , the Sedna -like objects, the extreme TNOs and the retrograde TNOs . Because of the conservation of angular momentum ,

8004-554: The formation of in situ hot Jupiters is not entirely in situ . If the atmosphere of a hot Jupiter is stripped away via hydrodynamic escape , its core may become a chthonian planet . The amount of gas removed from the outermost layers depends on the planet's size, the gases forming the envelope, the orbital distance from the star, and the star's luminosity. In a typical system, a gas giant orbiting at 0.02 AU around its parent star loses 5–7% of its mass during its lifetime, but orbiting closer than 0.015 AU can mean evaporation of

8120-531: The formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud . Most of the collapsing mass collected in the center, forming the Sun , while the rest flattened into a protoplanetary disk out of which the planets , moons , asteroids , and other small Solar System bodies formed. This model, known as the nebular hypothesis ,

8236-407: The future. Another example is Earth's axial tilt , which, due to friction raised within Earth's mantle by tidal interactions with the Moon ( see below ), is incomputable from some point between 1.5 and 4.5 billion years from now. The outer planets' orbits are chaotic over longer timescales, with a Lyapunov time in the range of 2–230 million years. In all cases, this means that the position of

8352-431: The gravitational disruption caused by galactic tides , passing stars and giant molecular clouds began to deplete the cloud, sending comets into the inner Solar System. The evolution of the outer Solar System also appears to have been influenced by space weathering from the solar wind, micrometeorites, and the neutral components of the interstellar medium . The evolution of the asteroid belt after Late Heavy Bombardment

8468-450: The heat of the photosphere the hot Jupiter is orbiting. There are several proposed hypotheses as to why this might occur. One such hypothesis involves tidal dissipation and suggests there is a single mechanism for producing hot Jupiters and this mechanism yields a range of obliquities. Cooler stars with higher tidal dissipation damps the obliquity (explaining why hot Jupiters orbiting cooler stars are well aligned) while hotter stars do not damp

8584-487: The high density, because it is likely composed mainly of hydrogen . The surface gravity is also high, over 50 times that of Earth. In 2012, the super-Jupiter Kappa Andromedae b was imaged around the star Kappa Andromedae , orbiting it about 1.8 times the distance at which Neptune orbits the Sun . This extrasolar-planet-related article is a stub . You can help Misplaced Pages by expanding it . Hot Jupiter Hot Jupiters (sometimes called hot Saturns ) are

8700-406: The host star failed to display many of the brightness and spectral characteristics associated with stellar flaring and solar active regions , including sunspots. Their statistical analysis also found that many stellar flares are seen regardless of the position of the exoplanet, therefore debunking the earlier claims. The magnetic fields of the host star and exoplanet do not interact, and this system

8816-427: The hot Jupiter with an orbit inclined relative to the star's rotation. The type II migration happens during the solar nebula phase, i.e. when gas is still present. Energetic stellar photons and strong stellar winds at this time remove most of the remaining nebula. Migration via the other mechanism can happen after the loss of the gas disk. Instead of being gas giants that migrated inward, in an alternate hypothesis

8932-429: The inner Solar System was populated by 50–100 Moon-to- Mars -sized protoplanets . Further growth was possible only because these bodies collided and merged, which took less than 100 million years. These objects would have gravitationally interacted with one another, tugging at each other's orbits until they collided, growing larger until the four terrestrial planets we know today took shape. One such giant collision

9048-467: The inner planets (Mercury, Venus, and possibly Earth) but not the outer planets, including Jupiter and Saturn. Afterward, the Sun would be reduced to the size of a white dwarf , and the outer planets and their moons would continue orbiting this diminutive solar remnant. This future development may be similar to the observed detection of MOA-2010-BLG-477L b , a Jupiter-sized exoplanet orbiting its host white dwarf star MOA-2010-BLG-477L . The Solar System

9164-463: The interaction of the magnetic fields of the star and its orbiting exoplanet, or because of tidal forces between them. These effects are called "star–planet interactions" or SPIs. The HD 189733 system is the best-studied exoplanet system where this effect was thought to occur. In 2008, a team of astronomers first described how as the exoplanet orbiting HD 189733 A reaches a certain place in its orbit, it causes increased stellar flaring . In 2010,

9280-489: The larger body. Astronomers estimate that the current state of the Solar System will not change drastically until the Sun has fused almost all the hydrogen fuel in its core into helium, beginning its evolution from the main sequence of the Hertzsprung–Russell diagram and into its red-giant phase. The Solar System will continue to evolve until then. Eventually, the Sun will likely expand sufficiently to overwhelm

9396-400: The larger moons of Saturn . A different scenario occurs when the moon is either revolving around the primary faster than the primary rotates or is revolving in the direction opposite the planet's rotation. In these cases, the tidal bulge lags behind the moon in its orbit. In the former case, the direction of angular momentum transfer is reversed, so the rotation of the primary speeds up while

9512-420: The last 20 years. Currently, many planetary scientists think that the Solar System might have looked very different after its initial formation: several objects at least as massive as Mercury may have been present in the inner Solar System, the outer Solar System may have been much more compact than it is now, and the Kuiper belt may have been much closer to the Sun. At the end of the planetary formation epoch,

9628-433: The mass consisted of heavier elements that were created by nucleosynthesis in earlier generations of stars. Late in the life of these stars, they ejected heavier elements into the interstellar medium . Some scientists have given the name Coatlicue to a hypothetical star that went supernova and created the presolar nebula. The oldest inclusions found in meteorites , thought to trace the first solid material to form in

9744-406: The mass of the locally growing hot Jupiter has a number of possible effects on neighboring planets. If the hot Jupiter maintains an eccentricity greater than 0.01, sweeping secular resonances can increase the eccentricity of a companion planet, causing it to collide with the hot Jupiter. The core of the hot Jupiter in this case would be unusually large. If the hot Jupiter's eccentricity remains small

9860-405: The metals and silicates that formed the terrestrial planets, allowing the giant planets to grow massive enough to capture hydrogen and helium, the lightest and most abundant elements. Planetesimals beyond the frost line accumulated up to 4  M E within about 3 million years. Today, the four giant planets comprise just under 99% of all the mass orbiting the Sun. Theorists believe it

9976-404: The modern asteroid belt, with dry asteroids and water-rich objects similar to comets. However, it is unclear whether conditions in the solar nebula would have allowed Jupiter and Saturn to move back to their current positions, and according to current estimates this possibility appears unlikely. Moreover, alternative explanations for the small mass of Mars exist. Gravitational disruption from

10092-399: The nebula spun faster as it collapsed. As the material within the nebula condensed, the temperature rose . The center, where most of the mass collected, became increasingly hotter than the surrounding disc. Over about 100,000 years, the competing forces of gravity , gas pressure, magnetic fields, and rotation caused the contracting nebula to flatten into a spinning protoplanetary disc with

10208-495: The net trend was for the inner planets to migrate inward as the disk dissipated, leaving the planets in their current orbits. The giant planets ( Jupiter , Saturn , Uranus , and Neptune ) formed further out, beyond the frost line , which is the point between the orbits of Mars and Jupiter where the material is cool enough for volatile icy compounds to remain solid. The ices that formed the Jovian planets were more abundant than

10324-410: The obliquity (explaining the observed misalignment). Another hypothesis is that the host star sometimes changes rotation early in its evolution, rather than the orbit changing. Yet another hypothesis is that hot Jupiters tend to form in dense clusters, where perturbations are more common and gravitational capture of planets by neighboring stars is possible. Ultra-hot Jupiters are hot Jupiters with

10440-594: The outer layers of the star to expand greatly, and the star will enter a phase of its life in which it is called a red giant . Within 7.5 billion years, the Sun will have expanded to a radius of 1.2 AU (180 × 10 ^  km; 110 × 10 ^  mi)—256 times its current size. At the tip of the red-giant branch , as a result of the vastly increased surface area, the Sun's surface will be much cooler (about 2,600 K (2,330 °C; 4,220 °F)) than now, and its luminosity much higher—up to 2,700 current solar luminosities. For part of its red-giant life,

10556-422: The outer planets' migration would have sent large numbers of asteroids into the inner Solar System, severely depleting the original belt until it reached today's extremely low mass. This event may have triggered the Late Heavy Bombardment that is hypothesised to have occurred approximately 4 billion years ago, 500–600 million years after the formation of the Solar System. However, a recent re-appraisal of

10672-533: The outer planets, possibly causing Neptune to surge past Uranus and plough into the ancient Kuiper belt. The planets scattered the majority of the small icy bodies inwards, while themselves moving outwards. These planetesimals then scattered off the next planet they encountered in a similar manner, moving the planets' orbits outwards while they moved inwards. This process continued until the planetesimals interacted with Jupiter, whose immense gravity sent them into highly elliptical orbits or even ejected them outright from

10788-413: The parent object without enough energy to entirely escape its gravity. Moons have come to exist around most planets and many other Solar System bodies. These natural satellites originated by one of three possible mechanisms: Jupiter and Saturn have several large moons, such as Io , Europa , Ganymede and Titan , which may have originated from discs around each giant planet in much the same way that

10904-409: The planet's surface or atmosphere. Such a fate awaits the moons Phobos of Mars (within 30 to 50 million years), Triton of Neptune (in 3.6 billion years), and at least 16 small satellites of Uranus and Neptune. Uranus's Desdemona may even collide with one of its neighboring moons. A third possibility is where the primary and moon are tidally locked to each other. In that case,

11020-416: The planet-forming disk to reform in the gas giant's wake. In the simulation, planets up to two Earth masses were able to form in the habitable zone after the hot Jupiter passed through and its orbit stabilized at 0.1 AU. Due to the mixing of inner-planetary-system material with outer-planetary-system material from beyond the frost line, simulations indicated that the terrestrial planets that formed after

11136-461: The planetesimal disc made the orbits of Uranus and Neptune near-circular again. In contrast to the outer planets, the inner planets are not thought to have migrated significantly over the age of the Solar System, because their orbits have remained stable following the period of giant impacts. Another question is why Mars came out so small compared with Earth. A study by Southwest Research Institute, San Antonio, Texas, published June 6, 2011 (called

11252-427: The planets and residual gas but between the planets and the remaining small bodies. As the large bodies moved through the crowd of smaller objects, the smaller objects, attracted by the larger planets' gravity, formed a region of higher density, a "gravitational wake", in the larger objects' path. As they did so, the increased gravity of the wake slowed the larger objects down into more regular orbits. The outer edge of

11368-422: The planets are likely to collide with each other or be ejected from the system in the next few billion years. Beyond this, within five billion years or so, Mars's eccentricity may grow to around 0.2, such that it lies on an Earth-crossing orbit, leading to a potential collision. In the same timescale, Mercury's eccentricity may grow even further, and a close encounter with Venus could theoretically eject it from

11484-415: The planets formed from the disc around the Sun. This origin is indicated by the large sizes of the moons and their proximity to the planet. These attributes are impossible to achieve via capture, while the gaseous nature of the primaries also makes formation from collision debris unlikely. The outer moons of the giant planets tend to be small and have eccentric orbits with arbitrary inclinations. These are

11600-402: The planets might have shifted due to gravitational interactions. Planetary migration may have been responsible for much of the Solar System's early evolution. In roughly 5 billion years, the Sun will cool and expand outward to many times its current diameter (becoming a red giant ), before casting off its outer layers as a planetary nebula and leaving behind a stellar remnant known as

11716-452: The points of origin for most observed comets . At their distance from the Sun, accretion was too slow to allow planets to form before the solar nebula dispersed, and thus the initial disc lacked enough mass density to consolidate into a planet. The Kuiper belt lies between 30 and 55 AU from the Sun, while the farther scattered disc extends to over 100 AU, and the distant Oort cloud begins at about 50,000 AU. Originally, however,

11832-405: The presolar nebula, are 4,568.2 million years old, which is one definition of the age of the Solar System. Studies of ancient meteorites reveal traces of stable daughter nuclei of short-lived isotopes, such as iron-60 , that only form in exploding, short-lived stars. This indicates that one or more supernovae occurred nearby. A shock wave from a supernova may have triggered the formation of

11948-503: The primary. If a moon is revolving in the same direction as the planet's rotation and the planet is rotating faster than the orbital period of the moon, the bulge will constantly be pulled ahead of the moon. In this situation, angular momentum is transferred from the rotation of the primary to the revolution of the satellite. The moon gains energy and gradually spirals outward, while the primary rotates more slowly over time. The Earth and its Moon are one example of this configuration. Today,

12064-436: The rate of centimetres per year over the course of the next few million years. The inner Solar System , the region of the Solar System inside 4 AU, was too warm for volatile molecules like water and methane to condense, so the planetesimals that formed there could only form from compounds with high melting points, such as metals (like iron , nickel , and aluminium ) and rocky silicates . These rocky bodies would become

12180-422: The result of giant collisions . Collisions between bodies have occurred continually up to the present day and have been central to the evolution of the Solar System. Beyond Neptune, many sub-planet sized objects formed. Several thousand trans-Neptunian objects have been observed. Unlike the planets, these trans-Neptunian objects mostly move on eccentric orbits, inclined to the plane of the planets. The positions of

12296-408: The satellite's orbit shrinks. In the latter case, the angular momentum of the rotation and revolution have opposite signs, so transfer leads to decreases in the magnitude of each (that cancel each other out). In both cases, tidal deceleration causes the moon to spiral in towards the primary until it either is torn apart by tidal stresses, potentially creating a planetary ring system, or crashes into

12412-698: The second but failed protostar, but Jupiter has far too little mass to trigger fusion in its core and so became a gas giant ; it is in fact younger than the Sun and the oldest planet of the Solar System. At this point in the Sun's evolution , the Sun is thought to have been a T Tauri star . Studies of T Tauri stars show that they are often accompanied by discs of pre-planetary matter with masses of 0.001–0.1  M ☉ . These discs extend to several hundred  AU —the Hubble Space Telescope has observed protoplanetary discs of up to 1000 AU in diameter in star-forming regions such as

12528-501: The stars they orbit, which would destabilize any satellite's orbit, the latter process being stronger for larger moons. This means that for most hot Jupiters, stable satellites would be small asteroid -sized bodies. Furthermore, the physical evolution of hot Jupiters can determine the final fate of their moons: stall them in semi-asymptotic semimajor axes, or eject them from the system where they may undergo other unknown processes. In spite of this, observations of WASP-12b suggest that it

12644-687: The strong radiation of nearby massive stars and ejecta from supernovae occurring close by. The various planets are thought to have formed from the solar nebula, the disc-shaped cloud of gas and dust left over from the Sun's formation. The currently accepted method by which the planets formed is accretion , in which the planets began as dust grains in orbit around the central protostar. Through direct contact and self-organization , these grains formed into clumps up to 200 m (660 ft) in diameter, which in turn collided to form larger bodies ( planetesimals ) of ~10 km (6.2 mi) in size. These gradually increased through further collisions, growing at

12760-473: The surface regolith will release into the atmosphere, creating a greenhouse effect that will heat the planet until it achieves conditions parallel to Earth today, providing a potential future abode for life. By 3.5 billion years from now, Earth's surface conditions will be similar to those of Venus today. Around 5.4 billion years from now, the core of the Sun will become hot enough to trigger hydrogen fusion in its surrounding shell. This will cause

12876-511: The sweeping secular resonances could also tilt the orbit of the companion. Traditionally, the in situ mode of conglomeration has been disfavored because the assembly of massive cores, which is necessary for the formation of hot Jupiters, requires surface densities of solids ≈ 10 g/cm , or larger. Recent surveys, however, have found that the inner regions of planetary systems are frequently occupied by super-Earth type planets. If these super-Earths formed at greater distances and migrated closer,

12992-475: The terrestrial region, between 2 and 4 AU from the Sun, is called the asteroid belt . The asteroid belt initially contained more than enough matter to form 2–3 Earth-like planets, and, indeed, a large number of planetesimals formed there. As with the terrestrials, planetesimals in this region later coalesced and formed 20–30 Moon- to Mars-sized planetary embryos ; however, the proximity of Jupiter meant that after this planet formed, 3 million years after

13108-399: The tidal bulge stays directly under the moon, there is no angular momentum transfer, and the orbital period will not change. Pluto and Charon are an example of this type of configuration. There is no consensus on the mechanism of the formation of the rings of Saturn. Although theoretical models indicated that the rings were likely to have formed early in the Solar System's history, data from

13224-422: Was available, and to have migrated outward to their current positions over hundreds of millions of years. The migration of the outer planets is also necessary to account for the existence and properties of the Solar System's outermost regions. Beyond Neptune , the Solar System continues into the Kuiper belt , the scattered disc , and the Oort cloud , three sparse populations of small icy bodies thought to be

13340-818: Was first developed in the 18th century by Emanuel Swedenborg , Immanuel Kant , and Pierre-Simon Laplace . Its subsequent development has interwoven a variety of scientific disciplines including astronomy , chemistry , geology , physics , and planetary science . Since the dawn of the Space Age in the 1950s and the discovery of exoplanets in the 1990s, the model has been both challenged and refined to account for new observations. The Solar System has evolved considerably since its initial formation. Many moons have formed from circling discs of gas and dust around their parent planets, while other moons are thought to have formed independently and later to have been captured by their planets. Still others, such as Earth's Moon , may be

13456-440: Was mainly governed by collisions. Objects with large mass have enough gravity to retain any material ejected by a violent collision. In the asteroid belt this usually is not the case. As a result, many larger objects have been broken apart, and sometimes newer objects have been forged from the remnants in less violent collisions. Moons around some asteroids currently can only be explained as consolidations of material flung away from

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