The solar system , in Astronomy, is the name given to the Planetary system composed of the Sun and the celestial objects revolving around him: the eight Planet natural satellite S, their 165 known (usually called the “moons”), three dwarf planets, and the billion small bodies (Asteroid frozen S, objects, Comet S, Météoroïde S, interplanetary dust, etc).

In a diagrammatic way, the solar system is divided between the Sun, four telluric planets internal, a Ceinture of asteroids made up of small rock bodies, four giant gas external and a second belt called Ceinture of Kuiper, composed of frozen objects. Beyond this belt a disc of scattered objects is, the Héliopause and, according to the theory advanced by Jan Oort, the Nuage of Oort.

The most moved away with moreover nearer, the planets of the system name Mercure, Venus, Ground, Mars, Jupiter, Saturn, Uranus and Neptune. Six of these planets have satellites in Orbite and each external planet is surrounded by a planetary Anneau of dust and other particles.

All planets, except the Earth, bear the names of God X and goddesses of the Roman Mythologie. The three dwarf planets are Pluton, the largest object known of the belt of Kuiper, Cérès, the largest known object of the belt of asteroids, and finally Éris which is in the disc of the scattered objects.

By extension, the term “solar system” is employed to indicate others planetary systems.

Terminology

The objects orbiting around the Sun are divided into three classes: Planet S, dwarf planets and small bodies.

A Planet is a body orbits about it around the Sun which is sufficiently massive to form a spherical form and cleaned its immediate vicinity of all the smaller objects. Eight planets are known: Mercury, Venus, the Ground, Mars, Jupiter, Saturn, Uranus, Neptune.

A dwarf Planet is, according to the official definition (decision of August 24th, 2006 of the international astronomical Union), a body in Orbite around the Sun which, if it is sufficiently massive to have a spherical form, did not make clear place in its vicinity. In October 2007, three bodies were officially indicated so that: Pluto, Éris and Cérès. Other bodies could the being in the future, such Sedna, Orcus or Quaoar.

All the other objects orbits about it around the sun are defined like Petits body of the solar system.

The natural satellite , or the moons, are the objects orbits about it around planets, of dwarf planets and the small bodies rather than around the Sun.

Structure

General information

The main component of the solar system is the Sun, a star of the principal Séquence of standard G2 which contains: 99.86% of all the known mass of the solar system and dominate it nellement Gravitation. Jupiter and Saturn, the two objects orbiting around the Sun most massive, gathers more than 90% of the remaining mass.

The majority of the large objects in orbit around the Sun are it in a plan close to that of the orbit Ground stre, named ecliptic. Typically, the plan of orbit of planets is very close to that of the ecliptic while the Comet S and the objects of the Ceinture of Kuiper have an orbit which forms an angle significantly larger compared to him.

All the planets and the majority of the other objects orbit in the same direction as the rotation of the Sun, i.e. in the opposite direction of the needles of a watch from the point of view of an observer located above the solar north pole. Certain objects orbit in a direction retrogresses, like the Halley's Comet.

The orbits of planets are almost circular. Those of the smaller bodies present eccentricity S various and can be strongly elliptic.

In an abstract way, the solar system is often divided into distinct zones. The internal solar system includes four telluric planets and girdles asteroids. The remainder of the system can be regarded simply as external solar system; others separate the area beyond Neptune from the four giant gas.

Sun

The Sun is the star of the solar system and by far its principal component. Like any star, its mass makes it possible the Densité in its heart to be sufficiently high to cause reactions of nuclear Fusion uninterrupted, which produces enormous quantities of energy, the major part radiated in electromagnetic space in the form of Rayonnement like the visible Lumière.

The Sun is a moderately large Naine yellow, but the name is misleading since the Sun is broader and more luminous than the average of stars of the Milky Way. It is located about the middle of the principal Séquence of the Diagramme of Hertzsprung-Russell; however, more brilliant stars and more heats which the Sun are rare while the less luminous and colder stars are current.

It is thought that the position of the Sun on the principal sequence indicates that it is far from to have exhausted its hydrogen reserves for nuclear fusion. It becomes gradually more brilliant: earlier in its history, its luminosity was lower of the three quarters than that of today.

The calculation of the relationship between hydrogen and the Hélium inside the Sun suggests that it is halfway of its life cycle. In five billion year, it will leave the principal sequence and will become larger, more shining, more cold and more red: a Giant red. At this time, its luminosity will be several thousands of times that of today.

The Sun is a star of population I; it was born towards the end from the evolution from the Univers. It contains more elements heavier than hydrogen and helium (of “metals” in the astronomical language) that the stars of population II. These metal elements were formed in the explosion of the cores of older stars and more doors. The old stars contain few metals while the later stars contain some more. It is thought that this high metallicity was essential to the development of the planetary system, because the planets are formed by metal accretion.

Interplanetary medium

In addition to the Light, the Sun radiates a continuous flow of particles charged (a plasma) called Solar wind. This flow extends at the approximate speed of: 1.5 million kilometers per hour, creating a thin atmosphere, the Heliosphere, which bathes the solar system until approximately 100 astronomical units (marking the Héliopause). The material composing the heliosphere is known under the name of interplanetary Milieu. The solar Cycle eleven years and frequent the solar eruptions and ejections of mass coronale disturb the heliosphere and create a space climate. The rotation of the solar magnetic field acts on the interplanetary medium to create the heliospheric Couche of current, the greatest structure of the solar system.

The Terrestrial magnetic field protects the atmosphere from the solar wind. Venus and Mars do not have a magnetic field and the solar wind gradually blows their atmosphere in space. On Earth, the interaction of the solar wind and terrestrial magnetic field cause the polar lights.

The heliosphere partly protects the solar system from the cosmic rays, protection increased on planets having magnetic field. The density of cosmic rays in the interstellar Environment and forces it solar magnetic field change over very long periods, therefore the cosmic level of radiation in the solar system varies, but one is unaware of of how much.

The interplanetary medium lodges at least two areas of cosmic dusts in the shape of disc. The first, the cloud of dust zodiacal, lies in the solar system interns and causes the Lumière zodiacale. It was probably formed by collisions inside the belt of asteroids caused by interactions with planets. The second extends from 10 to 40 UA and was probably created at the time of similar collisions in the belt of Kuiper, .

Internal solar system

The internal solar system traditionally indicates the area located between the Sun and the belt of asteroids. Composed mainly of Silicate S and metals, the objects of the internal solar system orbit very close to the Sun: the ray of the very whole area is smaller than the distance between Jupiter and Saturne.

Internal planets

The four internal planets have a dense and rock composition, little or not of natural satellite and no system of rings. They are mainly made up of minerals at raised melting point, the such Silicate S which form to them solid crust and them semi-fluid coat, and of metals like the Fer and the Nickel which compose to them core. Three of the four planets (Venus, Earth and Mars) have a substantial atmosphere; all show craters of impact and characteristics Tectonique S of surface like Rift S and Volcan S.

; Mercury:

Mercure is the planet nearest to the Sun (: 0.4 UA of Equatorial radius) as well as smallest (: 0.055 terrestrial mass). Mercury does not have any natural satellite and its only known geological characteristics, apart from the craters of impact, are dorsa, probably produced by contraction more early in its history. The atmosphere of Mercury, almost non-existent, is made of atoms torn off on its surface by the solar wind. The origin of its large iron core and its fine coat was still not explained in an adequate way. Among the hypothetical scenarios, it is possible that its external layers were swept by a giant impact or that it was stopped in its accretion by solar energy.

; Venus

Venus (: 0.7 UA) is close to the Earth in the face (: 0.815 terrestrial mass) and, like it, has a thick silicate coat surrounding a metal core, a significant atmosphere and an internal geological activity. However, it is much drier and its atmosphere is 90 times denser. Come does not have any satellite. It is about the hottest planet, with a temperature of surface upper than 400 °C, most probably because of the Greenhouse effect caused by its atmosphere. No recent geological activity was detected on Venus; its absence of magnetic field not making it possible to prevent the impoverishment of its atmosphere, that suggests however that it is réalimentée regularly by volcanic eruptions.

; Ground

the Ground (1 UA) is largest and densest of the internal planets, only whose one knows a recent geological activity and who shelters the Vie. Its Hydrosphère liquid is single among telluric planets and it is the only planet where an activity Tectonique was observed. The terrestrial atmosphere is radically different from that of another planets, having been deteriorated by the presence of forms of life to contain 21% of Oxygène. The Earth has a satellite, the the Moon, the only satellite significantly large of telluric planets of the solar system.

; March

Mars (: 1.5 UA) is smaller than the Earth and Venus (: 0.107 terrestrial mass). It has a held atmosphere, mainly of Carbon dioxide. Its surface, constellated with vast volcanos like Olympus Mons, with valleys, rifts like Valles Marineris, watch of the signs of a geological activity which perhaps persisted until recently. March has two small natural satellites (Déimos and Phobos), probably of the captured Astéroïde S.

Girdle asteroids

The Astéroïde S are mainly of Petits bodies of the solar system composed of rocks and not-volatile metal minerals.

The belt of asteroids occupies an orbit located between Mars and Jupiter, at a distance ranging between: 2.3 and: 3.3 UA of the Sun. It is thought that they are remainders of the solar system in formation which could not accréter in a larger body because of the gravitational Jupiter interferences.

The asteroids vary in the face of several hundred kilometers to microscopic dust. All the asteroids, except largest, Cérès, are regarded as small bodies, although some such Vesta or Hygie could be reclassified as dwarf planets if it is shown that they reached a hydrostatic balance.

The belt of asteroids contains tens of thousands, possibly million, objects of more than one kilometer in diameter. In spite of this, the total mass of the belt probably does not exceed thousandths of that of the Earth. The belt densément is very little densément populated; the space probes regularly crossed it without incident. The asteroids of a diameter ranging between 10 and 10-4 m are called Météoroïde S. ; Cérès:

Cérès (: 2.77 UA) is more the large body of the belt of asteroids and its only dwarf planet. Of a diameter slightly lower than: 1000 km, sufficient so that its own gravity gives him a spherical form, Cérès were regarded as a planet when he was discovered at the 19th century, then recategorized as asteroid in the years 1850 when observations revealed their abundance. It was again reclassified in 2006 like dwarf planet.

; Groups of asteroids:

the asteroids of the principal belt are divided into several groups and families according to their orbital characteristics. Certain asteroids comprise the moons, sometimes as broad as themselves. The belt also contains comets from where could come terrestrial water.

The internal solar system is also constellated with asteroids located apart from the belt and whose orbit crosses possibly that of telluric planets.

External solar system

Beyond the belt of asteroids an area dominated by the gas giant extends. Many a Comet S at short period, including the centaurs, also resides there.

The zone does not have a correctly definite traditional name. It is often mentioned external solar system, in opposition to the internal solar system, but the term recently started to be used exclusively for the zone located after the orbit of Neptune.

The solid objects of this area are composed of a greater proportion of “ices” (Eau, Ammoniac, Méthane) that their correspondents of the internal solar system.

External planets

The four external planets are giant gas and gather with them four 99% of the mass which orbits around the Sun. The atmosphere of Jupiter and Saturn is mainly made up of Hydrogène and Hélium; that of Uranus and Neptune contains a greater percentage of ices. It was suggested that they belong to a distinct category, the “frozen giants”. The four gas giants have systems of rings, but only those of Saturn can be easily observed since the Earth.

; Jupiter

Jupiter (: 5.2 UA), with 318 terrestrial masses, is as massive as: 2.5 times all another planets. It is primarily made up hydrogen and of helium. Its internal strong heat creates a certain number of semi-permanent characteristics in its atmosphere, like bands of clouds or the Grande red Spot. Jupiter has 63 known satellites; four larger, Ganymède, Callisto, Io and Europe, present similarities with telluric planets, like volcanicity. Ganymède, the largest satellite of the solar system, is larger than Mercure.

; Saturn

Saturn (: 9.5 UA), known for its system of rings, has characteristics similar to Jupiter, like its atmospheric composition. It is less massive (95 terrestrial masses) and has 60 known satellites (like 3 not confirmed); two of them, Titan and Encelade, present signs of geological activity, primarily of the Cryovolcan ism. Titan is larger than Mercure and is the only satellite of the solar system to have a substantial atmosphere.

; Uranus

Uranus (: 19.6 UA), with 14 terrestrial masses, is lightest of the gas giants. In a single way among planets of the solar system, it orbits the Sun on its side, the axis of its rotation being tilted of a little more 90° compared to the ecliptic . Its core is definitely colder than that of the other gas giants and radiates very little heat in space. Uranus has the 27 known satellites, largest being Titania, Obéron, Umbriel, Ariel and Miranda.

; Neptune

Neptune (: 30 UA), although smaller than Uranus, are slightly more massive (17 terrestrial masses) and consequently more dense. It radiates more internal heat, but not as much as Jupiter or Saturn. Neptune has 13 known satellites. Largest, Triton, is geologically active and present Geyser S of Azote liquidates. Triton is the only large satellite placed on an orbit retrogresses.

Comets

The comets are small bodies of the solar system, generally a few kilometers in diameter, mainly made up of volatile ices. They have highly eccentric orbits, with a Périhélie often located in the internal solar system and a Aphélie beyond Pluton. When a comet enters the internal solar system, the proximity of the Sun causes the sublimation and the Ionization of its surface, creating a tail: a long trail of gas and dust.

Comets at short period (as the Halley's Comet) traverse their orbit in less than two hundred years and would come from the Ceinture of Kuiper; the comets at long period (as the Comet Hauls-Bopp) have a periodicity of several thousands of years and would hold their origin of the Nuage of Oort. Others finally have a hyperbolic trajectory and would come from the outside of the solar system, but the determination of their orbit is difficult. The old comets which lost the majority of their compounds birds are often regarded as asteroids.

; Centaurs:

the centaurs, which extend between 9 and 30 UA, are frozen bodies similar to comets orbiting between Jupiter and Neptune. The largest known centaur, (10199) Chariklo, measurement between 200 and 250 km diameter. The first discovered centaur, (2060) Chiron, was regarded as a comet since it developed a cometary tail. Certain astronomers classify the centaurs as objects of the Ceinture of Kuiper scattered internal, equivalents of the scattered objects external.

Trojan asteroids

The Trojan asteroids are two groups of Astéroïde S located at the points of Lagrange L4 gold L5 of Jupiter (of the zones gravitationally stable ahead and behind of its orbit).

Neptune is also accompanied by some Trojan asteroids.

Area transneptunienne

The zone beyond Neptune, often called area transneptunienne, is always largely unexplored. It seems that it consists primarily of small bodies (largest having the fifth of the diameter of the Earth and a mass quite lower than that of the Moon) composed of rock and ice.

Girdle of Kuiper

The Belt of Kuiper, the principal structure of the area, is a large remains ring similar to the Ceinture of asteroids, but made up mainly of ice. It extends between 30 and 50 UA from the Sun. It is thought that the area is the source of comets of short-period.

It is mainly made up of small bodies, but several of the largest objects, like Quaoar, Varuna, or Orcus, could be reclassified like dwarf planets. One estimates at: 100000 the number of objects of the belt of Kuiper of a diameter higher than 50 km, but its total mass is estimated at a tenth, even a hundredth of that of the Earth. Several objects of the belt have multiple satellites and the majority are located on orbits which take them along apart from the plan of the ecliptic.

The belt of Kuiper can be coarsely divided between the “traditional” objects and those into Résonance with Neptune (for example the Plutino S, which traverses two orbits when Neptune traverses three of them, but there exist other reports/ratios).

The belt in resonance begins inside even from the orbit of Neptune. The traditional belt of the objects not having any resonance with Neptune extends between: 39.4 and: 47.7 UA. The members of this traditional belt are called Cubewano S, according to the first object of this kind to be discovered.

; Pluto and Charon

Pluto (39 UA on average), a dwarf Planet, is the largest known object of the belt of Kuiper. Discovered in 1930 and regarded as a Planet, it was reclassified in 2006 during the adoption of a formal definition of these various bodies. Pluto has a tilted eccentric orbit of 17° in the field of the ecliptic and which extends from: 29.7 UA with the perihelion with: 49.5 UA with the aphelion.

the largest moon of Pluto, Charon, is sufficiently large so that the unit revolves around a center of gravity located above the surface of each planet. The two other small moons, Nix and Hydra, orbit the couple Pluto-Charon.
Pluto east in orbital resonance 3:2 with Neptune (the planet orbits twice around the Sun when Neptune orbits three times). The objects of the belt of Kuiper which share this resonance are named Plutino S.

Scattered objects

The scattered objects extend well beyond the belt from Kuiper. It is thought that they come from this belt but were ejected by it by the gravitational influence of Neptune during its formation. The majority of the scattered objects have a perihelion in the belt of Kuiper and an aphelion which can reach 150 UA Soleil. In a typical way, their orbit is strongly inclined, often almost perpendicular to the ecliptic. Certain astronomers regard them as other elements of the belt of Kuiper and call besides them “scattered objects of the belt of Kuiper”.

; Éris

Éris (68 UA on average) is the largest known scattered object and caused a clarification of the planet statute besides to its discovery, since it is at least 5% larger than Pluton (diameter estimated of: 2400 km). It has the moon, Dysnomie. Like Pluto, its orbit is strongly eccentric (perihelion with: 38.2 UA, the average distance from Pluto to the Sun, perihelion with: 97.6 UA) and strongly tilted.

Remote areas

Héliopause

The Héliosphère is divided into two distinct areas. The Solar wind voyage at its maximum speed until approximately 95 UA, three times the average distance between Pluto and Sun. Then, the solar wind enters in collision with the winds opposed coming from the interstellar Milieu. It slows down, condenses and sudden turbulences, forming a great oval structure called the Héliogaine which resembles and behaves in a way rather similar to the tail of a comet, still extending on 40 UA in a direction and several times this distance in the opposite direction. The external limit of the heliosphere, the Héliopause, is the point where the solar wind dies out and where begins interstellar space.

The form of the héliopause is affected by the interactions with the interstellar environment, as by the solar magnetic fields dominating in the south (the northern hemisphere extends further 9 UA that the southern hemisphere). Beyond the héliopause, to approximately 230 UA of the Sun, a shock wave extends, a zone of plasma left by the Sun during its way through the Milky Way.

No space probe exceeded the héliopause and the conditions in interstellar space are not known. One knows enough little at which point the heliosphere protects the solar system from the cosmic rays. A specific mission was suggested.

Cloud of Oort

The Nuage of Oort is a hypothetical zone gathering until a trillion frozen objects and which one thinks that it is the source of comets at long period. It would surround the solar system towards: 50000 UA, perhaps even until: 100000 UA. It is thought that it would be composed of comets which were ejected internal solar system after interactions with the gas giants. The objects of the cloud of Oort move very slowly and can be affected by not very frequent events like the gravitational collisions, effects of a close star or a galactic Marée.

; Sedna and the internal cloud of Oort

Sedna is a large reddish object resembling Pluton whose pleasing very eccentric orbit with 76 UA of the Sun to the perihelion and with 928 UA with the aphelion and who takes: 12050 years with being traversed. Michael Brown, which discovered the object in 2003, declared that it cannot acts of a scattered object because its perihelion is too remote to have been affected by Neptune. He considers, with other astronomers, who it is about the first known member of a new population, which could include the object, which has a perihelion of 45 UA, an aphelion of 415 UA and an orbital period of: 3420 years. Brown names this population the “internal cloud of Oort” because it would have been formed according to a similar process, but at a less long distance from the Sun. Sedna is most probably a dwarf planet, even if its form is not known with certainty.

Limits

The limit between the solar system and interstellar space is not precisely defined. It is thought that the solar wind leaves the place to the interstellar Milieu with four times the distance between Pluton and the Sun. However, the Sphere of Hill of the Sun, i.e., its zone of gravitational influence, could extend up to thousand times further, up to 2 light-years (: 125000 UA). In spite of recent discoveries like that of Sedna, the zone located between the belt of Kuiper and the cloud of Oort are overall unknown. In addition, that located between the Sun and Mercury are always the subject of studies.

Formation

According to the assumption most usually accepted, the solar system was formed starting from the solar Nébuleuse, theory suggested for the first time in 1755 by Emmanuel Kant and independently formulated by Pierre-Simon Laplace. According to this theory, the solar system was formed there is: 4.6 billion years by gravitational collapse of a molecular Cloud giant. This cloud was broad of several light-years and probably gave rise to several stars. The studies of Météorite S reveal traces of element S which are produced only in the middle of very large star explosions, indicating that the Sun was formed inside a Amas of stars and near a certain number of Supernova E. The Shock wave of these supernovas perhaps caused the formation of the Sun by creating areas of surdensity in surrounding nebula, making it possible gravity to take the top on the internal pressure of gas and to initiate collapse.

The area which will become the solar system thereafter, known under the name of pre-solar nebula, had a diameter between: 7000 and: 20000 UA and masses very slightly higher than that of the Sun (in excess of: 0.001 with: 0.1 solar Mass). Progressively of its collapse, the conservation of the Angular momentum of nebula made it turn more quickly. While the matter condensed there, the Atome S returned there in collision more and more frequently. The center, where the majority of the mass had accumulated, became gradually hotter than the disc which it entourait, .

Star studies of the type T Tauri - young stellar masses not having started the operations of nuclear fusion and which one thinks that they are similar to the Sun at this stage of his evolution - show that they are often accompanied by discs pre-planet gears.

After 100 million years, the pressure and the density of the Hydrogène in the center of nebula became sufficiently high so that the protostar initiates the nuclear Fusion, increasing its size until a hydrostatic balance is reached, thermal energy counterbalancing the gravitational contraction. On this level, the Sun became a genuine star.

The other bodies of the solar system were formed remainder of the cloud of gas and dust. The current models make them be formed by Accrétion: initially grains of dust in orbit around central protostar, then clusters a few meters in diameter formed by direct contact, which returned in collision to constitute planétésimaux approximately 5 km in diameter. From there, their size increased by successive collisions at the average rate/rhythm of 15  cm per annum during the following million years.

The solar system interns was too hot so that the Molécule S birds such as the Eau or the Méthane condense: the planétésimaux ones which was formed there were relatively small (approximately: 0.6% of the mass of the disc).

Still further, where the frozen compounds volatile could remain solid, Jupiter and Saturne became giant gas. Uranus and Neptune captured less matter and one thinks that their core is mainly made of glaces, .

As soon as the Sun produced energy, the Solar wind blew gas and dust of the disc protoplanétaire, stopping the growth of planets. The stars of the type T Tauri have stellar winds definitely more intense than older stars and more stables, .

Future

The heat released by the Sun increases with the wire of time. One can even fear that with very long run (several hundreds of million years) it reaches a level such as the life will be impossible on Earth.

In approximately four billion and half of years, the Sun will have exhausted its hydrogen reserves, which will have been transformed into helium, and will change structure. Its core will contract but the whole star will become much bulkier. It should transform into Géante red, hundred times bulkier than at present. The closest planets, Mercury and Venus, the Ground and Mars should be destroyed.

It then will burn its helium rather quickly, which will further increase its size and its temperature, roasting completely the Ground with the passage. Once its completely consumed reserves of nuclear energy, the Sun will crumble on itself and will transform into white Naine very dense and not very luminous. It will cool gradually and end up more not radiating neither light nor heat, it will then have arrived at the stage of black Naine.

Our solar system makes it tower of the Galaxie in 250 million years. At the same time it oscillates on both sides of the galactic Plan with one period of 2 X 33 million years. It thus crosses this plan all the 33 million years what also constitutes the intermediate duration of the geological stages. These stages are defined according to important changes in fauna and the flora, sometimes due to Cataclysmes as with the passage Permien - Trias or with the passage Crétacé - Tertiaire. One can think that these changes are due to glaciations resulting from the meeting of the Earth with clouds of electron S of the galactic Plan. The last glaciations, those of the Quaternary , occurred whereas the solar system crossed the Plan of the Galaxy while going from the South towards North. It is an explanation which can indicate why the glaciations were much more marked in the Northern Hemisphere which directly received the electron S of the clouds of the galactic plane.

Galactic context

The solar system is located in the Milky Way, a barred Spiral galaxy of a diameter of approximately: 100000 light-years containing 200 billion stars. The Sun resides in one of the external spiral arms of the galaxy, the Bras of Orion, with between: 25000 and: 28000 light-years of the galactic Center. It there evolves/moves with approximately 220 km/s and carries out a revolution into 225 to 250 million years, a galactic Année.

The situation of the solar system in the galaxy is probably a factor of the evolution of the life on Earth. Its orbit is almost circular and is traversed about at the same speed as rotation of the spiral arms, which means that it crosses them only seldom. The spiral arms lodging definitely more Supernova E potentially dangerous, this provision made it possible the Earth to know long periods of interstellar stability. The solar system also resides apart from the zones rich in star around the galactic center. Close to the center, the gravitational influence of close stars would more often disturb the Nuage of Oort and would propel more comets towards the internal solar system, producing collisions with the potentially catastrophic consequences. The radiation of the galactic center would interfere with the development of complex forms of life.

Currently, the Sun moves in direction of the star Véga.

Vicinity

The immediate vicinity of the solar system is known under the name of local interstellar Nuage, a relatively dense zone inside an area which is it less, the local Bulle. This bubble is a cavity of the interstellar Milieu, in the form of sand glass of approximately 300 light-years broad. The bubble contains plasma at high-temperature in a very diluted way, which suggests that it is the product of several recent supernovas. One counts relatively few stars apart less than 10 light-years of the Sun. The system nearest is that of Alpha Centauri, a distant triple system of: 4.4 light-years. Alpha Centauri has and B are two close stars resembling the Sun, Alpha Centauri C (or Proxima Centauri) is a Naine red orbiting the pair with: 0.2 light-year. One finds then dwarf the reds of the star of Barnard (6 light-years), Wolf 359 (: 7.8 light-years) and Lalande 21185 (: 8.3 light-years). The largest star with less than 10 light-years is Sirius, a blue Naine brilliant twice more massive than the Sun around which orbit a white Naine named Sirius B; it is distant of: 8.6 light-years. The other systems in these 10 light-years are the binary system of dwarf reds Luyten 726-8 (: 8.7 light-years) and dwarf solitary red Ross 154 (: 9.7 light-years). The nearest simple star similar to the Sun is Tau Ceti, distant of: 11.9 light-years; it has 80% of the mass of the Sun, but only 60% of its luminosity. Nearest Exoplanète resembling the Earth which one knows, Gliese 581 C, is located at: 20.40 light-years.

Discovered and exploration

Pre-telescopic observations

The concept of solar system did not exist in a widespread way before one recent time. In general, the Earth was perceived like stationary in the center of the Univers and sometimes of intrinsically different nature to this one. A heliocentric cosmos was however postulated on several occasions, such as for example by the Greek philosopher Aristarque de Samos, the mathematician and Indian astronomer Aryabhata or the astronomer Polish Nicolas Copernic. Nevertheless, the conceptual projections of the 17th century, led by Galileo Galilei, Johannes Kepler and Isaac Newton, popularized the idea that the Earth moved not only around the Sun, but that the same physical laws applied to another planets.

The five planets closest to the Earth (Mercury, Venus, Mars, Jupiter and Saturne) are among the more brilliant objects of the sky and were named " πλανήτης" ( planētēs , meaning “wandering”) by the Greek astronomers in Antiquity. Except the Sun, they are the only members of the solar system known before the telescopic observations .

Telescopic observations

The first observations of the solar system as such were carried out starting from the use of the Télescope by the astronomers. Galileo was the first to discover physical details on other bodies: it observed that the the Moon was covered with crater S, that the Sun had spots and that four satellites orbited Jupiter. Christiaan Huygens continued the discoveries of Galileo by discovering Titan, the Saturn satellite, and forms it rings of this planet Jean-Dominique Cassini discovered then the four other moons of Saturn, the Division of Cassini in its rings and the Grande red spot on Jupiter.

Edmond Halley realized into 1705 that the repeated appearances of a comet related to the same object, returning regularly all the 75 to 76 years. It was the first proof that another thing which the planets orbited around the Sun.

In 1781, William Herschel observed what he thought of being a new comet, but whose orbit revealed that it was about a new planet, Uranus.

Giuseppe Piazzi discovered Cérès in 1801, a small body located between Mars and Jupiter which was initially regarded as a new planet. Later observations revealed thousands of other objects in the same area, which leads to their reclassification like Astéroïde S.

The differences between the position of Uranus and theoretical calculations of its orbit led to suspecter that another more remote planet disturbed the movement of it. Calculations of Urbain the Glassmaker allowed the discovery of Neptune in 1846. The precession of the advance of the perihelion of Mercure also led the Glassmaker to postulate the existence of a planet located between Mercure and the Sun, Vulcan in 1859, which at the end of the day proved to be a false track. The anomalies of trajectory of external planets made put forth by Percival Lowell the assumption of a Planet X. After its death, the Observatoire Lowell undertook a research which leads to discovered of Pluton by Clyde Tombaugh in 1930. Pluto proved to be too small to disturb the orbits of the gas giants and its discovery was a coincidence. Cérès, he was initially regarded as a planet before being reclassified in 2006 like dwarf Planet , .

Mike Brown, Chadwick Trujillo and David L. Rabinowitz announced the discovery of Éris in 2005, a scattered Objet larger than Pluton, and besides the greatest overdraft orbits about it around the Sun since Neptune.

Mechanical scanning

Since the beginning of the space era, many missions of exploration by space probes were implemented. All the planets of the solar system were visited with various degrees by robotized probes: at least, of the photographs were taken by it, and in certain cases of the undercarriages tests carried out on the grounds and the atmospheres.

The first human object launched in space was the Soviet satellite Sputnik 1 in 1957, which orbited the Earth for 3 months. The American probe To explore 6 , launched in 1959, was the first satellite to return an image of the Earth taken of space. The first probe to travel successfully towards another body was Luna 1 which exceeded the Moon in 1959; at the origin, it was to strike it but missed its target and becomes the first artificial object to enter in solar orbit. Mariner 2 was the first probe to fly over another planet, Venus, in 1962. The first successful overflight of Mars was carried out by Mariner 4 in 1964; Mercury was approached by Mariner 10 in 1974.

The first probe to explore external planets was Pioneer 10 , which flew over Jupiter in 1973. Pioneer 11 visited Saturn in 1979. The two probes Voyager carried out an overflight of all the gas giants starting from their launching in 1977. They flew over Jupiter in 1979 and Saturne in 1980 and 1981. Voyager 2 continued by an overflight of Uranus in 1986 and Neptune in 1989. The probes Voyager are on the way of the Héliogaine and the Héliopause; according to NASA, they met the final Choc with approximately 93 UA of the Sun. No object of the belt of Kuiper was still visited by a probe, but New Horizons , launched on January 19th, 2006, is on the way for this area; the probe must fly over Pluton in July 2015, as thereafter of other bodies if that proves to be possible. In 1966, the Moon became the first object of the solar system apart from the Earth with being orbited by an Artificial satellite ( Luna 10 ), followed per Mars in 1971 ( Mariner 9 ), Venus in 1975 ( Venera 9 ), Jupiter in 1995 ( Galileo , which carried out the first overflight of an asteroid, (951) Gaspra, in 1991), the asteroid (433) Eros in 2000 ( NEAR Shoemaker ) and Saturn in 2004 ( Cassini-Huygens ). The probe MESSENGER is currently on the Mercury way which it should orbit in 2011, while Dawn should reach the asteroid Vesta in 2011 and dwarf planet Cérès in 2015.

The first probe to be posed on another body was the Soviet probe Luna 2 , which impacted the Moon in 1959. The Venus surface was reached in 1966 ( Venera 3 ), Mars in 1971 ( March 3 , although the first landing over Mars was carried out only by Viking 1 in 1976), (433) Eros in 2001 ( NEAR Shoemaker ) and the Saturn satellite Titan in 2005 ( Huygens ). The orbitor Galileo also released a probe in the atmosphere of Jupiter in 1995; the gas giantess not having surface strictly speaking, the probe was destroyed by the temperature and the pressure at the time of her descent.

Human exploration

The human exploration of the solar system for the moment is limited to the immediate surroundings of the Earth. The first human being to have reached space (defined as a altitude of more than 100 km) and to orbit the Earth was the Soviet Cosmonaute Youri Gagarine on April 12th, 1961. The first man to go on another surface of the solar system fur the American Astronaut Neil Armstrong, which lands on the Moon on July 21st, 1969. The first Orbit station being able to lodge more than one passenger was the American Skylab , which accommodated teams of three astronauts between 1973 and 1974. The first permanent station was the Soviet space station Mir , which was occupied continuously between 1989 and 1999. Its successor, the International space station, lodged a human presence in space since then.

References

See too

Internal bonds

External bonds

  • Astronoo : formation of the solar system
  • Astrofiles: the solar system
  • the solar system
  • the solar system with range of your mouse
  • the solar system - pioneer-astro
  • Videoconference on the topic: " The system solaire" (intervention of Andre Brahic)

Beats-smg: Saulės sėstėma Nds-nl: Zunnesysteem Simple: Solar system Zh-min-nan: Thài-iông-hē Zh-yue: 太陽系

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