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104-520: Data shows a dramatic increase in crustal production from 125–120 Ma to 70 Ma, largely in East Pacific Rise areas, although the marked increase in production rates of crustal material was also seen in the Gondwana ridges, as well as in oceanic plateaus . This period of increased crustal production is interpreted as a superplume event. This "pulse" of increased crustal production peaked soon after

208-459: 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

312-464: 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

416-423: 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

520-557: 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

624-422: 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

728-565: 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

832-425: 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

936-486: 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

1040-522: 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

1144-467: Is a large upwelling of material. Normal upwellings in the mantle are a common occurrence, as it is generally accepted that these upwellings are the driving force behind mantle convection and subsequent plate motion. In the case of the upwelling in the mid- Cretaceous period along the East Pacific Rise, its origin lies deep within the Earth, near the core–mantle boundary. This conclusion is taken from

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1248-524: Is a planet's "original" crust. It forms from solidification of a magma ocean. Toward the end of planetary accretion , the terrestrial planets likely had surfaces that were magma oceans. As these cooled, they solidified into crust. This crust was likely destroyed by large impacts and re-formed many times as the Era of Heavy Bombardment drew to a close. The nature of primary crust is still debated: its chemical, mineralogic, and physical properties are unknown, as are

1352-491: Is debated. The anorthosite highlands of the Moon are primary crust, formed as plagioclase crystallized out of the Moon's initial magma ocean and floated to the top; however, it is unlikely that Earth followed a similar pattern, as the Moon was a water-less system and Earth had water. The Martian meteorite ALH84001 might represent primary crust of Mars; however, again, this is debated. Like Earth, Venus lacks primary crust, as

1456-435: Is needed to create tertiary crust, and Earth is the only planet in the Solar System with plate tectonics. Earth's crust is a thin shell on the outside of Earth, accounting for less than 1% of Earth's volume. It is the top component of the lithosphere , a division of Earth's layers that includes the crust and the upper part of the mantle . The lithosphere is broken into tectonic plates that move, allowing heat to escape from

1560-404: 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

1664-450: 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,

1768-434: 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

1872-405: 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

1976-566: 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

2080-445: 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

2184-434: 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"

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2288-476: 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,

2392-462: 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

2496-473: 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

2600-568: 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

2704-421: The adiabatic rise of mantle causes partial melting. Tertiary crust is more chemically-modified than either primary or secondary. It can form in several ways: The only known example of tertiary crust is the continental crust of the Earth. It is unknown whether other terrestrial planets can be said to have tertiary crust, though the evidence so far suggests that they do not. This is likely because plate tectonics

2808-839: The nebular hypothesis , 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

2912-625: 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

3016-403: 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

3120-438: 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

3224-454: 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

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3328-527: 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

3432-455: 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

3536-468: 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

3640-602: The Solar System There is evidence that 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

3744-400: 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

3848-492: 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

3952-570: 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

4056-475: 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

4160-576: 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

4264-417: 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

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4368-506: 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

4472-532: 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

4576-498: 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

4680-457: 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

4784-430: 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

4888-732: The case of icy satellites, it may be distinguished based on its phase (solid crust vs. liquid mantle). The crusts of Earth , Mercury , Venus , Mars , Io , the Moon and other planetary bodies formed via igneous processes and were later modified by erosion , impact cratering , volcanism, and sedimentation. Most terrestrial planets have fairly uniform crusts. Earth, however, has two distinct types: continental crust and oceanic crust . These two types have different chemical compositions and physical properties and were formed by different geological processes. Planetary geologists divide crust into three categories based on how and when it formed. This

4992-422: 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

5096-560: 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

5200-439: 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

5304-452: 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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5408-423: The crust ranges between about 20 and 120 km. Crust on the far side of the Moon averages about 12 km thicker than that on the near side . Estimates of average thickness fall in the range from about 50 to 60 km. Most of this plagioclase-rich crust formed shortly after formation of the Moon, between about 4.5 and 4.3 billion years ago. Perhaps 10% or less of the crust consists of igneous rock added after

5512-400: 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

5616-459: 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

5720-649: 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,

5824-453: The entire planet has been repeatedly resurfaced and modified. Secondary crust is formed by partial melting of mostly silicate materials in the mantle, and so is usually basaltic in composition. This is the most common type of crust in the Solar System. Most of the surfaces of Mercury, Venus, Earth, and Mars comprise secondary crust, as do the lunar maria . On Earth secondary crust forms primarily at mid-ocean spreading centers , where

5928-410: 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,

6032-416: The fact that the Earth retained a constant field polarity at the same time that this upwelling occurred. A more current superplume/superswell is in the southern and eastern region of Africa. Seismic analysis shows a large low-shear-velocity province , which coincides with a region of upwelling of semi-liquid material which is a poor conductor of seismic waves . While there are several processes at work in

6136-467: 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 ,

6240-463: The formation of the initial plagioclase-rich material. The best-characterized and most voluminous of these later additions are the mare basalts formed between about 3.9 and 3.2 billion years ago. Minor volcanism continued after 3.2 billion years, perhaps as recently as 1 billion years ago. There is no evidence of plate tectonics . Study of the Moon has established that a crust can form on a rocky planetary body significantly smaller than Earth. Although

6344-522: The formation of these high topography zones, lithospheric thinning and lithospheric heating have been unable to predict the topographic upwelling on the African plate. Dynamic topography models have, on the other hand, been able to predict this upwelling utilizing calculations of the instantaneous flow of Earth's mantle. Isotopic samples taken from the Pacific-Antarctic ridge basalts have disassembled

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6448-407: 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

6552-431: 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

6656-491: The igneous mechanisms that formed them. This is because it is difficult to study: none of Earth's primary crust has survived to today. Earth's high rates of erosion and crustal recycling from plate tectonics has destroyed all rocks older than about 4 billion years , including whatever primary crust Earth once had. However, geologists can glean information about primary crust by studying it on other terrestrial planets. Mercury's highlands might represent primary crust, though this

6760-490: The initial plume (between 120 Ma and 100 Ma), and then declined over the next thirty million years. Along with the increase in crustal output from ridges, there is an extended period in the time frame from 125 Ma to 40 Ma where the Earth's magnetic field reversal frequency declines sharply. The last remnants of this superplume event are the South Pacific superswell located underneath Tahiti . Superplume/superswell creation

6864-429: 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

6968-467: 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

7072-416: The interior of Earth into space. A theoretical protoplanet named " Theia " is thought to have collided with the forming Earth, and part of the material ejected into space by the collision accreted to form the Moon. As the Moon formed, the outer part of it is thought to have been molten, a " lunar magma ocean ". Plagioclase feldspar crystallized in large amounts from this magma ocean and floated toward

7176-489: 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

7280-400: 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

7384-420: 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,

7488-639: The long-held belief that there was a coherent geochemical province stretching from the Australian–Antarctic discordance to the Juan de Fuca plate. Instead, samples have shown that there are instead two distinct geochemical domains above and below the Easter microplate. Measurements of the average depth of ridge axes also shows that this boundary line lies on the southeastern side of the Darwin Rise /Pacific superswell. It

7592-433: 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

7696-405: 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

7800-404: 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

7904-399: 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

8008-491: 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

8112-594: 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,

8216-422: 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

8320-533: 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

8424-413: 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

8528-409: 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,

8632-461: 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

8736-427: 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

8840-422: 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

8944-415: 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

9048-402: 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

9152-452: 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,

9256-405: 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

9360-503: 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,

9464-428: The radius of the Moon is only about a quarter that of Earth, the lunar crust has a significantly greater average thickness. This thick crust formed almost immediately after formation of the Moon. Magmatism continued after the period of intense meteorite impacts ended about 3.9 billion years ago, but igneous rocks younger than 3.9 billion years make up only a minor part of the crust. Formation and evolution of

9568-436: 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

9672-455: The region of the South Pacific superswell, the age progression of the island chain is much shorter than models have predicted. Also, the path that these island chains take does not coincide with the motion of the plate. Crust (geology) In geology , the crust is the outermost solid shell of a planet , dwarf planet , or natural satellite . It is usually distinguished from the underlying mantle by its chemical makeup; however, in

9776-422: 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

9880-408: 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

9984-688: 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

10088-687: 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

10192-473: 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

10296-444: The surface. The cumulate rocks form much of the crust. The upper part of the crust probably averages about 88% plagioclase (near the lower limit of 90% defined for anorthosite ): the lower part of the crust may contain a higher percentage of ferromagnesian minerals such as the pyroxenes and olivine , but even that lower part probably averages about 78% plagioclase. The underlying mantle is denser and olivine-rich. The thickness of

10400-475: 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

10504-399: 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

10608-422: 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

10712-465: Was concluded that this upwelling was responsible for the disparity between the two geochemical regions. One of the many ways that plate motions are mapped is by using hotspot activity and volcanic island chains. It is assumed that hotspots are stable relative to the motion of the island chain, and is therefore used as a point of reference. In the case of the Marquesas Islands , an island chain in

10816-440: 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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