Solar System Material from Wikipedia the free encyclopedia
The solar system is a planetary system that includes the central star the Sun and all natural space objects orbiting the Sun.
It was formed by gravitational compression of a gas dust cloud about 4.57 billion years ago.
2].
Most of the mass of objects in the Solar System falls on the Sun; the rest is contained in eight relatively isolated planets with almost circular orbits and located within an almost flat disk - the plane of the ecliptic.
The total mass of the system is about 1,0014 M☉.
The four smaller inner planets Mercury, Venus, Earth [19] and Mars (also called the planets of the Earth group) — consist mainly of silicates and metals.
The four outer planets Jupiter, Saturn, Uranus and Neptune (also called gas giants) - are much more massive than the terrestrial planets.
The largest planets of the Solar system, Jupiter and Saturn, consist mainly of hydrogen and helium; the outer, smaller Uranus and Neptune, in addition to hydrogen and helium, contain methane and carbon monoxide in their atmospheres.
20].
Such planets are allocated to a separate class of "ice giants" [21].
Six of the eight planets and four dwarf planets have natural satellites.
Each of the outer planets is surrounded by rings of dust and other particles.
There are two regions in the Solar system filled with small bodies.
The asteroid belt, located between Mars and Jupiter, is similar in composition to the planets of the Earth group, since it consists of silicates and metals.
The largest objects of the asteroid belt are the dwarf planet Ceres and the asteroids Pallas, Vesta and Hygeia.
Beyond the orbit of Neptune are trans Neptunian objects consisting of frozen water, ammonia and methane, the largest of which are Pluto, Sedna, Haumea, Makemake, Quavar, Orc and Eris.
There are other populations of small bodies in the Solar system, such as planetary quasi satellites and Trojans, near Earth asteroids, centaurs, damocloids, as well as comets, meteoroids and cosmic dust moving through the system.
The solar wind (the flow of plasma from the Sun) creates a bubble in the interstellar medium, called the heliosphere, which extends to the edge of the scattered disk.
The hypothetical Oort cloud, which serves as the source of long period comets, can extend to a distance of about a thousand times further than the heliosphere.
The solar system is part of the Milky Way galaxy.
Content
The Solar System
The solar system in the artist's view.
The scales of distances from the Sun are not observed.
General characteristics Age
4,5682±0.0006 billion years[1][2]
Location Local Interstellar cloud, Local Bubble, Orion arm, Milky Way, Local group of Galaxies Mass
1,0014 M☉
Nearest star
Proxima Centauri (4.21-4.24 holy years) [3] Alpha Centauri system (4.37 sv. years)[4]
Nearest exoplanet
Alpha Centauri B b (4.37 sv. years)[5]
The planetary system is the most distant planet from the Sun
Neptune (4,503 billion km, 30.1 AU) [6]
Distance to ~30-50 AU [7] Kuiper belt Number of stars
1 (Sun)
Number of known planets
8, maybe 9
Number of dwarf planets
5[8]
Number of satellites
415 (172 for planets and 243 for small bodies of the solar system)[9][10]
The number of small bodies
more than 700,000 (as of November 2016)[9]
Number of comets
3441 (as of November 2016)[9]
1 Structure 1.1 Terminology 2 Composition 2.1 Sun 2.1.1 Interplanetary Environment 2.2 Inner region of the Solar System 2.2.1 Terrestrial planets 2.2.1.1 Mercury 2.2.1.2 Venus 2.2.1.3 Earth 2.2.1.4 Mars 2.2.2 Asteroid Belt 2.2.2.1 Asteroid Groups 2.2.2.2 Ceres 2.3 Outer region of the Solar System 2.3.1 Giant Planets 2.3.1.1 Jupiter 2.3.1.2 Saturn 2.3.1.3 Uranus 2.3.1.4 Neptune 2.3.1.5 Ninth Planet 2.3.2 Comets 2.3.3 Centaurs 2.3.4 Trans Neptunian objects 2.3.4.1 Kuiper Belt 2.3.4.1.1 Pluto 2.3.4.1.2 Haumea 2.3.4.1.3 Makemake 2.3.4.2 Scattered disk 2.3.4.2.1 Eris 2.4 Remote regions 2.4.1 Heliosphere 2.4.2 Oort Cloud 2.4.2.1 Sedna 2.5 Boundary regions 3 Comparative table of the main parameters
of planets and dwarf planets 4 Formation and evolution of the Solar System 4.1 Stability of the Solar System 5 "Discovery" and exploration of the Solar System 5.1 Observations 5.2 Geocentric and heliocentric systems 5.3 Studies of the Solar System 6 Colonization of the Solar System 7 Galactic Orbit 7.1 Surroundings 8 See also 9 Notes 10 References 11 References
Rotation around the galactic center Inclination to 60.19° of the plane of the Milky Way Distance to 27,170 ± 1,140 st. years of the galactic (8330 ± 350 pc)[11] center Treatment period
225-250 million years[12]
Orbital velocity
220-240 km / s[13]
Properties associated with the star Spectral G2 V[14] [15] class Snow line
~5 A. E. [16][17]
The boundary of the heliosphere
~113-120 A. E. [18]
Radius of the Hill sphere
~1-2 holy years
Structure The central object of the Solar system is the Sun a main sequence star of the spectral class G2V, a yellow dwarf.
The vast majority of the entire mass of the system is concentrated in the Sun (about 99.866 %), it holds the planets and other bodies belonging to the Solar system by its gravity[22].
The four largest objects — gas giants make up 99 % of the remaining mass (at the same time, most of it falls on Jupiter and Saturn — about 90 %).
Most large objects orbiting the Sun move in almost the same plane, called the ecliptic plane.
At the same time, comets and Kuiper Belt objects often have large angles of inclination to this plane[23][24].
All the planets and most other objects revolve around the Sun in the same direction as the rotation of the Sun (counterclockwise, if viewed from the north pole of the Sun).
There are exceptions, such as Halley's comet.
Mercury has the greatest angular velocity — it manages to make a complete revolution around the Sun in just 88 Earth days.
And for the most distant planet — Neptune the period of rotation is 165 earth years.
Most of the planets rotate around their axis in the same direction as they orbit the Sun.
The exceptions are Venus and Uranus, and Uranus rotates almost "lying on its side" (the axis tilt is about 90°).
A special device — tellurium is used to visually demonstrate the rotation.
Orbits of Solar system objects, in scale (clockwise, starting from the upper left part)
Many models of the Solar system conventionally show the orbits of planets at regular intervals, but in reality, with few exceptions, the farther a planet or belt is from the Sun, the greater the distance between its orbit and the orbit of the previous object.
For example, Venus is approximately 0.33 AU farther from the Sun than Mercury, while Saturn is 4.3 AU farther from Jupiter, and Neptune is 10.5 AU farther from Uranus.
There have been attempts to deduce correlations between orbital distances (for example, the Titius Bode rule)[25], but none of the theories has become generally accepted.
The orbits of objects around the Sun are described by Kepler's laws.
According to them, each object turns along an ellipse, in one of the foci of which the Sun is located.
Objects closer to the Sun (with a smaller semi major axis) have a higher angular velocity of rotation, so the rotation period (year) is shorter.
In an elliptical orbit, the distance of an object from the Sun changes during its year.
The closest point of the object's orbit to the Sun is called perihelion, the most distant is aphelion.
Each object moves the fastest in its perihelion and the slowest in its aphelion.
The orbits of the planets are close to a circle, but many comets, asteroids and Kuiper Belt objects have highly elongated elliptical orbits.
Most of the planets in the Solar System have their own subordinate systems.
Many are surrounded by satellites, some of the satellites are larger than Mercury.
Most large satellites are in synchronous rotation, one side of them is constantly facing the planet.
The four largest planets gas giants also have rings, thin bands of tiny particles that rotate in very close orbits almost in unison.
Terminology Sometimes The solar system is divided into regions.
The inner part of the Solar System includes four terrestrial planets and an asteroid belt.
The outer part begins outside the asteroid belt and includes four gas giants.
26].
After the discovery of the Kuiper Belt, the most remote part of the Solar System is considered to be the region consisting of objects located further than Neptune[27].
All objects of the Solar System orbiting the Sun are officially divided into three categories: planets, dwarf planets and small bodies of the Solar system.
A planet is any body in orbit around the Sun that turned out to be massive enough to acquire a spherical shape, but not massive enough to start thermonuclear fusion, and managed to clear the vicinity of its orbit of planetesimals.
According to this definition, there are eight known planets in the Solar System: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune Pluto does not meet this definition, because it has not cleared its orbit of the surrounding Kuiper Belt objects.
28].
A dwarf planet is a celestial body orbiting the Sun; it is massive enough to maintain a shape close to a round shape under the influence of its own gravitational forces; but it has not cleared the space of its orbit from planetesimals and is not a satellite of the planet[28].
By this definition, y The Solar system has five recognized dwarf planets: Ceres, Pluto, Haumea, Makemake and Eris.
29].
In the future, other objects may be classified
planets: Ceres, Pluto, Haumea, Makemake and Eris[29].
In the future, other objects may be classified as dwarf planets, for example, Sedna, Orc and Quavar.
30].
Dwarf planets whose orbits are located in the region of trans Neptunian objects are called plutoids[31].
The remaining objects orbiting the Sun are small bodies of the Solar system.
28].
The terms gas, ice and rock are used to describe various classes of substances found everywhere in the Solar system.
The stone is used to describe compounds with high condensation or melting temperatures that remained in the protoplanetary nebula in a solid state under almost all conditions[32].
Stone compounds usually include silicates and metals such as iron and nickel[33].
They predominate in the inner part of the Solar System, forming most of the terrestrial planets and asteroids.
Gases are substances with extremely low melting points and high saturated vapor pressure, such as molecular hydrogen, helium and neon, which have always been in a gaseous state in the nebula[32].
They dominate the middle part of the Solar System, making up most of Jupiter and Saturn.
Ices of substances such as water, methane, ammonia, hydrogen sulfide and carbon dioxide[33] have melting points up to several hundred kelvins, while their thermodynamic phase depends on the ambient pressure and temperature[32].
They can occur as ices, liquids or gases in various regions of the Solar System, while in the nebula they were in the solid or gas phase[32].
Most of the satellites of the giant planets contain icy substances, they also make up most of Uranus and Neptune (the so called "ice giants") and numerous small objects located beyond the orbit of Neptune[33][34].
Gases and ices are classified together as volatile substances[35].
Composition The Sun Interplanetary medium The inner region of the Solar system of the Earth group planets 1.
Mercury 2.
Venus 3.
Earth Moon 4.
Mars satellites of Mars Asteroid Belt Ceres Outer region of the Solar System Giant Planets 5.
Jupiter moons of Jupiter rings of Jupiter 6.
Saturn the moons of Saturn the rings of Saturn 7.
Uranus satellites of Uranus rings of Uranus 8.
Neptune satellites of Neptune rings of Neptune Comets Centaurs Trans Neptunian objects Kuiper Belt Pluto [36] satellites of Pluto Haumea [37] satellites of Haumea Makemake S/2015 (136472) 1 Scattered disk of Eris
Disnomy Remote regions Heliosphere Oort Cloud Sedna Various mnemonic techniques can be used to facilitate memorizing the names and order of the 8 planets.
The sun is the star of the Solar system and its main component.
Its mass (332,900 Earth masses)[38] is large enough to maintain a thermonuclear reaction in its bowels[39], in which a large amount of energy is released, radiated into space mainly in the form of electromagnetic radiation, the maximum of which falls on the wavelength range of 400-700 nm, corresponding to visible light[40].
According to the stellar classification, the Sun is a typical yellow dwarf of the G2 class.
This name can be misleading, since compared to most stars in our Galaxy, the Sun is a fairly large and bright star[41].
The class of a star is determined by its position on the Hertzsprung Russell diagram, which shows the relationship between the brightness of stars and their surface temperature.
Usually, hotter stars are brighter.
Most of the stars are located on the so called main sequence of this diagram, the Sun is located approximately in the middle of this sequence.
Brighter and hotter stars than the Sun are relatively rare, and dimmer and colder stars (red dwarfs) are common, accounting for 85 % of the stars in the Galaxy[41][42].
The position of the Sun on the main sequence shows that it has not yet exhausted its supply of hydrogen for nuclear fusion and is approximately in the middle of its evolution.
Now the Sun is gradually becoming brighter, at earlier stages of development its brightness was only 70% of today's[43].
The sun is a type I star of the stellar population, it was formed at a relatively late stage of the development of the Universe and therefore is characterized by a higher content of elements heavier than hydrogen and helium (in astronomy it is customary to call such elements "metals") than older type II stars[44].
Elements heavier than hydrogen and helium are formed in the cores of the first stars, so before the universe could be enriched with these elements, the first generation of stars had to pass.
The oldest stars contain few metals, and younger stars contain more of them.
It is assumed that high metallicity was extremely important for the formation of a planetary system in the Sun, because planets are formed by the accretion of"metals" [45].
Interplanetary environment
Planets of the Solar system
Transit of Venus on the disk of the Sun
Along with light, the Sun emits a continuous stream of charged particles (plasma), known as the solar wind.
This stream of particles propagates at a speed of about 1.5 million km per hour[46], filling the near solar region and creating a kind of analogue of the planetary atmosphere (heliosphere) at the Sun, which is at a distance of at least 100 AU from the Sun[47].
It is known as the interplanetary medium.
Manifestations of activity on the surface of the Sun, such as solar flares and coronal mass ejections, disturb the heliosphere, giving rise to space weather[48].
The largest structure within the heliosphere is the heliospheric current layer; a spiral surface created by the influence of the rotating magnetic field of the Sun on the interplanetary medium[49][50].
The Earth's magnetic field prevents the solar wind from disrupting the Earth's atmosphere.
Venus and Mars do not have a magnetic field, and as a result, the solar wind gradually blows their atmospheres into space[51].
Coronal mass ejections and similar phenomena change the magnetic field and remove a huge amount of matter from the surface of the Sun about 109-1010 tons per hour[52].
Interacting with the Earth's magnetic field, this substance falls mainly into the upper circumpolar layers of the Earth's atmosphere, where such interaction causes auroras, most often observed near the magnetic poles.
Cosmic rays originate from outside the Solar system.
The heliosphere and, to a lesser extent, the planetary magnetic fields of the heliospheric current layer partially protect the Solar System from external influences.
Both the density of cosmic rays in the interstellar medium and the strength of the Sun's magnetic field change over time, so the level of cosmic radiation in the Solar System is unstable, although the magnitude of deviations is not reliably known[53].
The interplanetary medium is the site of the formation of at least two disk like regions of cosmic dust.
The first, the zodiacal dust cloud, is located in the inner part of the Solar System and is the reason why the zodiacal light arises.
It probably arose due to collisions within the asteroid belt caused by interactions with planets[54].
The second region extends from about 10 to 40 AU and probably arose after similar collisions between objects within the Kuiper Belt [55][56].
The inner region of the Solar System The inner part includes the planets of the Earth group and asteroids.
Consisting mainly of silicates and metals, the objects of the inner region are relatively close to the Sun, this is the smallest part of the system — its radius is less than the distance between the orbits of Jupiter and Saturn.
The planets of the Earth group Four inner planets consist mainly of heavy elements, have a small number (0-2) of satellites, they do not have rings.
To a large extent, they consist of refractory minerals, such as silicates, which form their mantle and crust, and metals, such as iron and nickel, which form their core.
The three inner planets Venus, Earth, and Mars have atmospheres; all have impact craters and tectonic terrain details, such as rift basins and volcanoes[57][58][59][60][61][62].
Mercury
The planets of the Earth group.
From left to right: Mercury, Venus, Earth and Mars (scale dimensions, interplanetary distances none)
Mercury (0.4 AU from the Sun) is the closest planet to the Sun and the smallest planet in the system (0.055 Earth masses).
The planet has no satellites.
Characteristic details of the relief of its surface, in addition to impact craters, are numerous blade shaped ledges extending for hundreds of kilometers.
It is believed that they arose as a result of tidal deformations at an early stage of the planet's history at a time when the periods of Mercury's rotation around the axis and around the Sun did not enter into resonance[63].
Mercury has an extremely rarefied atmosphere, it consists of atoms "knocked out" from the planet's surface by the solar wind[64].
The relatively large iron core of Mercury and its thin crust have not yet been satisfactorily explained.
There is a hypothesis suggesting that the outer layers of the planet, consisting of light elements, were torn off as a result of a giant collision, as a result of which the size of the planet decreased[65].
Alternatively, the radiation of the young Sun could prevent the complete accretion of matter[66].
Venus
Venus is close in size to the Earth (0.815 Earth mass) and, like the Earth, has a thick silicate shell around the iron core and an atmosphere (because of this, Venus is often called the" sister " of the Earth).
There is also evidence of its internal geological activity.
However, the amount of water on Venus is much less than that of Earth, and its atmosphere is ninety times denser.
Venus has no moons.
This is the hottest planet in our system, its surface temperature exceeds 400 °C.
The most likely reason for such a high temperature is the greenhouse effect, which occurs due to a dense atmosphere rich in carbon dioxide[67].
Obvious secrets no signs of current geological activity have been detected on Venus, but since it does not have a magnetic field that would prevent the depletion of its dense atmosphere, this allows us to assume that its atmosphere is regularly replenished by volcanic eruptions[68].
Earth
The Earth is the largest and densest of the inner planets.
The Earth has plate tectonics.
The question of the existence of life anywhere other than the Earth remains open[69].
Among the planets of the Earth group, the Earth is unique (primarily due to the hydrosphere).
The Earth's atmosphere is radically different from the atmospheres of other planets — it contains free oxygen[70].
The Earth has one natural satellite the Moon, the only large satellite of the planets of the terrestrial group of the Solar system.
Mars
Mars is smaller than Earth and Venus (0.107 Earth masses).
It possesses an atmosphere consisting mainly of carbon dioxide with a surface pressure of 6.1 mbar (0.6 % of that of Earth)[71].
There are volcanoes on its surface, the largest of which, Olympus, exceeds the size of all terrestrial volcanoes, reaching a height of 21.2 km[72].
Rift depressions (Mariner Valleys), along with volcanoes, indicate former geological activity, which, according to some data, continued even during the last 2 million years[73].
The red color of the surface of Mars is caused by a large amount of iron oxide in its soil[74].
The planet has two moons Phobos and Deimos.
It is assumed that they are captured asteroids[75].
For today (after Earth) Mars is the most thoroughly studied planet in the Solar system.
Asteroids are the most common small bodies of the Solar system.
The asteroid belt occupies an orbit between Mars and Jupiter, between 2.3 and 3.3 AU from the Sun.
Hypotheses about the existence of a planet between Mars and Jupiter (for example, the hypothetical planet Phaeton) were put forward, but in the end were not confirmed, which in the early stages of the formation of the Solar System collapsed so that its fragments became asteroids that formed the asteroid belt.
According to modern views, asteroids are the remnants of the formation of the Solar System (planetozimals), which were unable to unite into a large body due to gravitational perturbations of Jupiter[76].
The sizes of asteroids vary from several meters to hundreds of kilometers.
All asteroids are classified as small bodies of the Solar System, but some bodies currently classified as asteroids, for example, Vesta and Hygeia, can be reclassified as dwarf planets if they are shown to maintain hydrostatic equilibrium[77].
Asteroid Belt (white) and Trojan asteroids (green)
The belt contains tens of thousands, possibly millions of objects larger than one kilometer in diameter[78].
Despite this, the total mass of asteroids in the belt is hardly more than one thousandth of the mass of the Earth[79].
Celestial bodies with diameters from 100 microns to 10 m are called meteoroids[80].
Even smaller particles are considered cosmic dust.
Asteroid groups
Asteroids are grouped into groups and families based on the characteristics of their orbits.
Asteroid satellites are asteroids orbiting other asteroids.
They are not so clearly defined as satellites of planets, being sometimes almost as large as their companion.
The asteroid belt also contains comets of the main asteroid belt, which may have been a source of water on Earth[81].
Trojan asteroids are located at the Lagrange points L4 and L5 of Jupiter (gravitationally stable regions of the planet's influence that move together with it in its orbit); the term "Trojans" is also used for asteroids located at the Lagrange points of any other planets or satellites (in addition to the Jupiter Trojans, the Trojans of Neptune, Earth, Uranus and Mars are known).
Asteroids of the Hilda family are in resonance with Jupiter 2:3, that is, they make three revolutions around the Sun during two full revolutions of Jupiter[82].
There are also groups of asteroids in the inner Solar System with orbits located from Mercury to Mars.
The orbits of many of them intersect the orbits of the inner planets[83].
Ceres
Ceres (2.77 AU) is a dwarf planet and the largest body of the asteroid belt.
Ceres has a diameter of a little less than 1000 km and enough mass to maintain a spherical shape under the influence of its own gravity.
After the discovery, Ceres was classified as a planet, but since further observations led to the discovery of a number of asteroids near Ceres, in the 1850s it was classified as an asteroid[84].
It was re classified as a dwarf planet in 2006.
The outer region of the Solar System is the location of gas giants and their satellites, as well as trans Neptunian objects, asteroid comet gas Kuiper belts, the Scattered Disk and the Oort cloud.
The orbits of many short period comets, as well as centaur asteroids, also pass in this area.
Solid objects in this region, due to their greater distance from the Sun, and therefore a much lower temperature, contain ices of water, ammonia and methane.
There are hypotheses about the existence in the outer region of the planet Tyuhe and, possibly, any other "Planets X", as well as the star of the satellite of the Sun Nemesis.
The four giant planets, also called gas giants, all together contain 99 % of the mass of matter orbiting the Sun.
Jupiter and Saturn are mainly composed of hydrogen and helium; Uranus and Neptune have a large ice content in their composition.
Because of this, some astronomers classify them in their own category — "ice giants" [85].
All four gas giants have rings, although only the ring system of Saturn is easily observed from Earth.
Jupiter
Giant planets.
From left to right: Jupiter, Saturn, Uranus and Neptune (scale dimensions, interplanetary distances none)
Jupiter has a mass 318 times larger than Earth's, and 2.5 times more massive than all the other planets combined.
It consists mainly of hydrogen and helium.
Jupiter's high internal temperature causes many semi permanent vortex structures in its atmosphere, such as cloud bands and the Great Red Spot.
Jupiter has 67 known satellites.
The four largest — Ganymede, Callisto, Io and Europa — are similar to the planets of the Earth group in such phenomena as volcanic activity and internal heating[86].
Ganymede, the largest moon in the Solar system, is larger than Mercury.
Saturn
Saturn, known for its extensive ring system, has a somewhat similar structure to Jupiter's atmosphere and magnetosphere.
Although the volume of Saturn is 60% of the Jovian, the mass (95 Earth masses) is less than a third of the Jovian; thus, Saturn is the least dense planet in the Solar system (its average density is less than the density of water).
Saturn has 62 confirmed satellites; two of them, Titan and Enceladus, show signs of geological activity.
This activity, however, is not similar to the Earth's, since it is largely due to the activity of ice[87].
Titan, which is larger than Mercury, is the only satellite in the Solar system with a significant atmosphere.
Uranus
With a mass 14 times that of Earth, Uranus is the lightest of the outer planets.
What makes it unique among other planets is that it rotates "lying on its side": the inclination of its axis of rotation to the plane of the ecliptic is approximately 98°[88].
If other planets can be compared to spinning tops, then Uranus is more like a rolling ball.
It has a much colder core than other gas giants, and radiates very little heat into space[89].
Uranus has 27 satellites discovered; the largest are Titania, Oberon, Umbriel, Ariel and Miranda.
Neptune
Neptune, although slightly smaller than Uranus, is more massive (17 Earth masses) and therefore denser.
It emits more internal heat, but not as much as Jupiter or Saturn[6].
Neptune has 14 known moons.
The largest is Triton, which is geologically active, with geysers of liquid nitrogen[90].
Triton is the only large satellite moving in the opposite direction.
Neptune is also accompanied by asteroids called Neptune Trojans, which are in resonance with it 1:1.
The ninth planet
On January 20, 2016, astronomers from the California Institute of Technology Konstantin Batygin and Michael Brown announced a possible ninth planet on the outskirts of the Solar System, outside the orbit of Pluto.
The planet is about ten times more massive than Earth, is about 20 times farther away from the Sun than Neptune (90 billion kilometers), and makes a revolution around the Sun in 10,000-20,000 years.
91].
According to Michael Brown, the probability that this planet really exists is " perhaps 90 %"[92].
So far, scientists call this hypothetical planet simply "The Ninth Planet"[93] (Eng. Planet Nine).
Comets are small bodies of the Solar system, usually only a few kilometers in size, consisting mainly of volatile substances (ice).
Their orbits have a large eccentricity, usually with a perihelion within the orbits of the inner planets and an aphelion far beyond Pluto.
When a comet enters the inner region of the Solar System and approaches the Sun, its icy surface begins to evaporate and ionize, creating a long cloud of gas and dust, often visible from Earth with the naked eye.
Short period comets have a period of less than 200 years.
The period of long period comets can be thousands of years.
It is believed that the source of short period comets is the Kuiper Belt, while the source of long period comets, such as the Hale — Bopp comet, is considered to be the Oort cloud.
Many comet families, such as the Near Solar Kreutz comets, were formed as a result of the decay of a single body[94].
Some comets with hyperbolic orbits may be from outside the Solar System, but determining their exact orbits is difficult[95].
Old comets, in which most of their volatile substances have already evaporated, are often classified as asteroids[96].
Centaurs
The Hale — Bopp Comet
Centaurs are icy comet like objects with a large semi axis larger than that of Jupiter (5.5 AU) and smaller than that of Neptune (30 AU).
The largest known centaur, Chariclo, has a diameter of approximately 250 km[97].
The first discovered centaur, Chiron, is also classified as a comet (95P), due to the fact that as it approaches the Sun, it develops a coma, like comets[98].
Trans Neptunian objects The space beyond Neptune, or the "region of trans Neptunian objects", is still largely unexplored.
Presumably, it contains only small bodies, consisting mainly of rocks and ice.
This region is sometimes also included in the "outer Solar system", although more often this term is used to refer to the space beyond the asteroid belt and up to the orbit of Neptune.
Kuiper Belt
The Kuiper Belt is a region of relics from the time of the formation of the Solar System, it is a large belt of fragments, similar to the asteroid belt, but consists mainly of ice[99].
It extends between 30 and 55 AU from the Sun.
It is composed mainly of small bodies of the Solar system, but many of the largest objects of the Kuiper Belt, such as Kvavar, Varuna and Orc, can be reclassified as dwarf planets after clarifying their parameters.
It is estimated that more than 100,000 Kuiper Belt objects have a diameter of more than 50 km, but the total mass of the belt is only one tenth or even one hundredth of the mass of the Earth[100].
Many objects of the belt have multiple satellites[101], and most objects have orbits located outside the ecliptic plane[102].
Known Kuiper Belt objects (green), shown relative to the four outer planets.
The scale is shown in astronomical units.
The dark area at the bottom of the picture is an area located for an earthly observer against the background of the Milky Way, the brightness of the stars of which does not allow you to distinguish dim objects
the angle of inclination to the ecliptic[104].
The Kuiper Belt can be roughly divided into "classical" and resonant objects (mainly plutinos)[99].
Resonant objects are in orbital resonance with Neptune (for example, making two revolutions for every three revolutions of Neptune, or one for every two).
The resonant objects closest to the Sun may cross the orbit of Neptune.
Classical Kuiper Belt objects are not in orbital resonance with Neptune and are located at a distance of approximately 39.4 to 47.7 AU from the Sun[103].
Elements of the classical Kuiper belt are classified as cubivano, from the index of the first detected object — (15760) 1992 QB1 ("QB1" is pronounced as "q bi wan"); and have orbits close to circular with a small
Pluto
Pluto is a dwarf planet, the largest known object of the Kuiper Belt.
After its discovery in 1930, it was considered the ninth planet; the situation changed in 2006 with the adoption of a formal definition of a planet.
Pluto has a moderate eccentricity of the orbit with an inclination of 17 degrees to the Ecliptic plane, and he is approaching the Sun at a distance of 29.6 and.
E., appearing closer to him Neptune, is removed on 49,3 and.
E. Unclear situation with the largest satellite of Pluto — Charon: whether it will continue to be classified as a moon of Pluto or will be reclassified as a dwarf planet.
Since the center of mass of the Pluto — Charon system is located outside their surfaces, they can be considered as a binary planetary system.
Four smaller moons — Nycta, Hydra, Kerber and Styx — orbit Pluto and Charon.
Pluto is located with Neptune in an orbital resonance of 3:2 — for every three revolutions of Neptune around the Sun, there are two revolutions of Pluto, the entire cycle takes 500 years.
Kuiper Belt objects whose orbits have the same resonance are called plutinos[105].
Haumea
Haumea is a dwarf planet.
It has a strongly elongated shape and a rotation period around its axis of about 4 hours.
The two moons and at least eight other trans Neptunian objects are part of the Haumea family, which formed billions of years ago from ice fragments after a large collision destroyed the Haumea ice mantle.
The orbit of the dwarf planet has a large inclination — 28°.
Makemake
Makemake originally designated as 2005 FY9, was named in 2008 and was declared a dwarf planet[29].
Currently, it is the second most visible brightness in the Kuiper Belt after Pluto.
The largest of the known classical objects of the Kuiper belt (not in confirmed resonance with Neptune).
Makemake has not yet found any satellites.
It has a diameter of 50 to 75 % of the diameter of Pluto, the orbit is inclined by 29°[106], the eccentricity is about 0.16.
Scattered disk
The scattered disk partially overlaps with the Kuiper Belt, but extends much further beyond it and is assumed to be the source of short period comets.
It is assumed that the objects of the scattered disk were thrown into disorderly orbits by the gravitational influence of Neptune during its migration at the early stage of the formation of the Solar System: one of the concepts is based on the assumption that Neptune and Uranus formed closer to the Sun than they are now, and then moved to their modern comparative sizes of the largest TNOs and orbits[107][108][109].
Many objects of the scattered disk (SDO) of the Earth.
they have a perihelion within the Kuiper Belt, but their aphelion can Images of objects links to articles extend up to 150 au from the Sun.
The orbits of objects are also very inclined to the ecliptic belt and are often almost perpendicular to it.
Some astronomers believe that the scattered disk is a region of the Kuiper Belt, and describe the objects of the scattered disk as "scattered objects of the Kuiper belt" [110].
Some astronomers also classify centaurs as inward scattered objects of the Kuiper Belt, along with outward scattered objects of the scattered disk[111].
Erida
Eris (68 AU on average) is the largest known object of the scattered disk.
Since its diameter was originally estimated at 2,400 km, that is, at least 5 % larger than that of Pluto, its discovery gave rise to disputes about what exactly should be called a planet.
It is one of the largest known dwarf planets[112].
Eris has one satellite — Dysnemia.
Like Pluto, its orbit is extremely elongated, with a perihelion of 38.2 AU (the approximate distance of Pluto from the Sun) and an aphelion of 97.6 AU; and the orbit is strongly (44.177°) inclined to the plane of the ecliptic.
Remote areas The question of where exactly the Solar system ends and interstellar space begins is ambiguous.
The key factors in their determination are two factors: the solar wind and solar gravity.
The outer boundary of the solar wind is the heliopause, beyond which the solar wind and interstellar matter mix, mutually dissolving.
The heliopause is located about four times farther than Pluto and is considered the beginning of the interstellar medium.
However, it is assumed that the region in which the Sun's gravity prevails over the galactic one — the Hill sphere extends a thousand times further.
113].
The interstellar medium in the vicinity of the Solar system is heterogeneous.
Observations show that the Sun is moving at a speed of about 25 km / s through the Local interstellar cloud and may leave it within the next 10 thousand years.
The solar wind plays an important role in the interaction of the Solar system with interstellar matter.
Our planetary system exists in an extremely rarefied" atmosphere " of the solar wind — a stream of charged particles (mainly hydrogen and helium plasma), flowing out of the solar corona at great speed.
The average speed of the solar wind observed on Earth is 450 km / s.
This velocity exceeds the velocity of propagation of magnetohydrodynamic waves, so when interacting with obstacles, the solar wind plasma behaves similarly to a supersonic gas flow.
As we move away from the Sun, the density of the solar wind weakens, and there comes a moment when it is no longer able to contain the pressure of interstellar matter.
During the collision, several transition regions are formed.
At first, the solar wind slows down, becomes more dense, warm and turbulent[114].
The moment of this transition is called the boundary of the shock wave (English termination shock) and is located at a distance of about 85-95 AU from the Sun[114] (according to data obtained from the Voyager 1[115] and Voyager 2[116] space stations, which crossed this boundary in December 2004 and August 2007).
After about another 40 AU, the solar wind collides with interstellar matter and finally stops.
This boundary separating the interstellar medium from the matter of the Solar system is called the heliopause[47].
In shape, it looks like a bubble, stretched out in the opposite direction to the movement of the Sun.
The region of space bounded by the heliopause is called the heliosphere.
According to the Voyager spacecraft, the shock wave from the south side was closer than from the north (73 and 85 astronomical units, respectively).
The exact reasons for this are still unknown; according to the first assumptions, the asymmetry of the heliopause may be caused by the action of ultra weak magnetic fields in the interstellar space of the Galaxy[116].
On the other side of the heliopause, at a distance of about 230 AU from the Sun, along the head shock wave (bow shock), the interstellar matter flying into the Solar System is decelerated from cosmic velocities[117].
No spacecraft has yet emerged from the heliopause, so it is impossible to know for sure the conditions in the local interstellar cloud.
It is expected that Voyagers will pass the heliopause approximately between 2014 and 2027 and will transmit valuable data on radiation levels and solar wind [118].
It is not clear enough how well the heliosphere protects the Solar System from cosmic rays.
A team funded by NASA has developed the concept of the "Vision Mission" mission sending a probe to the border of the heliosphere[119][120].
In June 2011, it was announced that thanks to the Voyager research, it became known that the magnetic field at the border of the Solar System has a structure similar to foam.
This is due to the fact that magnetized matter and small space objects form local magnetic fields, which can be compared to bubbles[121].
The Oort Cloud The hypothetical Oort cloud is a spherical cloud of icy objects (up to a trillion) that serves as a source of long period comets.
The estimated distance to the outer boundaries of the Oort cloud from the Sun is from 50,000 AU (approximately 1 light year) to 100,000 AU (1.87 sv.years).
It is believed that the objects that make up the cloud formed near the Sun and were scattered far into space by the gravitational effects of giant planets at an early stage of the development of the Solar System Objects of the Oort cloud move very slowly and can experience interactions that are unusual for internal objects of the system: rare collisions with each other, the gravitational influence of a passing star, the action of galactic tidal forces.
122][123].
There are also unconfirmed hypotheses about the existence of a gas giant planet Tyukhe near the inner boundary of the Oort cloud (30 thousand AU) and, possibly, any other "Planets X" in the cloud, including according to the hypothesis of an ejected fifth gas giant.
Sedna
A drawing illustrating the supposed view of the Oort cloud
Sedna (525.86 AU on average) is a large, Pluto like, reddish object with a giant, extremely elongated elliptical orbit, from about 76 AU at perihelion to 1000 AU at aphelion and a period of about 11,500 years.
Michael Brown, who discovered Sedna in 2003, argues that it cannot be part of the scattered disk or the Kuiper Belt, since its perihelion is too far away to be explained by the impact of Neptune's migration.
He and other astronomers believe that this object is the first discovered in an entirely new population, which may also include object 2000 CR105 with a perihelion of 45 AU, an aphelion of 415 AU and an orbital period of 3420 years[124].
Brown calls this population the "inner Oort cloud" because it probably formed through a process similar to that of the Oort cloud formation, although much closer to the Sun[125].
Sedna, very likely, could be recognized as a dwarf planet if its shape was reliably determined.
Border areas Most of our solar system is still unknown.
According to estimates, the Sun's gravitational field dominates over the gravitational forces of surrounding stars at a distance of about two light years (125,000 to a. E.).
In comparison, lower bounds of the radius of the Oort cloud do not place it on 50 000 a.
E.[126]
Despite the open objects such as Sedna, the region between the Kuiper belt and the Oort cloud with a radius of tens of thousands.
E., and especially very Oort cloud and what may be behind him, still practically unexplored.
There is an unconfirmed hypothesis about the existence of a satellite star of the Sun Nemesis in the boundary region (beyond the outer boundaries of the Oort cloud).
The study of the region between Mercury and the Sun is also continuing in the hope of detecting hypothetically possible volcanoid asteroids, although the hypothesis put forward about the existence of a large planet Vulcan there has been refuted[127].
Comparative table of the main parameters of planets and dwarf planets All the parameters below, except for density, distance from the Sun and satellites, are indicated in relation to similar data of the Earth.
Planet (dwarf planet)
Diameter, relative to
Mass, relative to
Mercury Venus Earth [129] Mars Ceres Jupiter Saturn Uranus Neptune Pluto Haumea Makemake Erida
0,382 0,949 1,0 0,53 0,074 11,2 9,41 3,98 3,81 0,186
0,055 0,815 1,0 0,107 0,00015 318 95 14,6 17,2 0,0022 0,00066
~0,11 [131] 0,116 0,182
~0,0005 [132] 0,0028
Orbital period radius, revolutions, a.
e. earth years 0,38 0,72 1,0 1,52 2,76 5,20 9,54 19,22 30,06 39,2[130] 43[130] 45,4[130] 67,8[130]
0,241 0,615 1,0 1,88 4,6 11,86 29,46 84,01 164,79 248,09 281,1 306,28 558,04
Day, relative to 58,6 243[128] 1,0 1,03 0,378 0,414 0,426 0,718[128] 0,671 6,387[128] 0,163 0,324 1,1
Density, kg/m3 5427 5243 5515 3933 2161 1326 687 1270 1638 1860 ~2600 ~1700 [133] 2520
Satellites 0 0 1 2 0 67 62 27 14 5 2 1 1
Distances of planets from the Sun: 1) Mercury 2) Venus 3) Earth 4) Mars Asteroid Belt 5) Jupiter 6) Saturn 7) Uranus 8) Neptune — Kuiper Belt
Approximate ratio of the size of the planets and the Sun.
Interplanetary distances are not on a scale.
The sun is depicted on the left.
Formation and evolution of the Solar system
The life cycle of the Sun.
The scale and colors are conditional.
Timeline in billions of years (approximately)
According to the currently accepted hypothesis, the formation of the Solar System began about 4.6 billion years ago with the gravitational compression of a small part of a giant interstellar gas dust cloud.
This initial cloud was probably several light years in size and was the progenitor for several stars[134].
In the process of compression, the size of the gas dust cloud decreased and, by virtue of the law of conservation of angular momentum, the speed of rotation of the cloud increased.
The center, where most of the mass gathered, became more and more hot than the surrounding disk[134].
Due to the rotation, the compression rates of the cloud in parallel and perpendicular to the rotation axis differed, which led to the flattening of the cloud and the formation of a characteristic protoplanetary disk with a diameter of about 200 AU[134] and a hot, dense protostar in the center[135].
It is believed that at this stage of evolution, the Sun was a T type star of Taurus.
Studies of T type Taurus stars show that they are often surrounded by protoplanetary disks with masses of 0.001-0.1 solar masses, with the overwhelming percentage of the nebula mass concentrated directly in the star[136].
The planets were formed by accretion from this disk[137].
Within 50 million years, the pressure and density of hydrogen in the center of the protostar became high enough to start a thermonuclear reaction 138].
Temperature, reaction rate, pressure, and density increased until a hydrostatic equilibrium was reached with thermal energy opposing the force of gravitational compression.
At this stage, the Sun became a full fledged main sequence star[139].
The solar system, as far as we know today, will last until the Sun begins to develop outside the main sequence of the Hertzsprung — Russell diagram.
As the Sun burns up its hydrogen fuel reserves, the released energy that supports the core tends to run out, causing the Sun to shrink.
This increases the pressure in its interior and heats the core, thus accelerating the combustion of fuel.
As a result, the Sun becomes brighter by about ten percent every 1.1 billion years [140], and will become even 40 % brighter over the next 3.5 billion years[141].
Approximately 7 [142] billion years from now, the hydrogen in the solar core will be completely
Approximately 7 [142] billion years from now, the hydrogen in the solar core will be completely converted into helium, which will complete the main sequence phase; The sun will become a subgiant[142].
In another 600 million years, the outer layers of the Sun will expand by about 260 times compared to the current size — the Sun will pass to the stage of a red giant[143].
Due to the extremely increased surface area, it will be much cooler than when located on the main sequence (2600 K)[143].
Having increased dramatically, the Sun is expected to absorb the nearest planets Mercury and Venus[144].
The Earth will probably avoid being absorbed by the outer solar shells[141], but will become completely lifeless, as the habitable zone will shift to the outer edges of the Solar System[145].
Eventually, as a result of the development of thermal instabilities[145][143], the outer layers of the Sun will be ejected into the surrounding space, forming a planetary nebula, in the center of which only a small stellar core will remain — a white dwarf, an unusually dense object half the original mass of the Sun, but only the size of the Earth[142].
This nebula will return some of the material that formed the Sun to the interstellar medium.
Stability of the Solar system At the moment, it is unclear whether the Solar system is stable.
It can be shown that if it is unstable, then the characteristic decay time of the system is very long[146].
The fact that man was forced to observe the movements of the heavenly bodies from the surface of the Earth rotating around its axis and moving in orbit, for many centuries prevented the understanding of the structure of the Solar System.
The apparent movements of the Sun and planets were perceived as their true movements around the stationary Earth.
The following objects of the Solar System can be observed with the naked eye from Earth: the Sun, Mercury, Venus (both shortly before sunrise or immediately after sunset), Mars, Jupiter and Saturn; as well as the Moon.
With binoculars or a small telescope, you can observe the 4 largest satellites of Jupiter (the so called Galilean satellites), Uranus, Neptune and Titan (the largest satellite of Saturn).
With the naked eye, you can also observe many comets as they approach the Sun.
At high magnification, you can see sunspots, the phases of Venus, the rings of Saturn and the Cassini gap between them[147].
Geocentric and heliocentric systems For a long time, the geocentric model was dominant, according to which the stationary Earth rests in the center of the universe, and all the celestial bodies move around it according to rather complex laws.
This system was most fully developed by the ancient mathematician and astronomer Claudius Ptolemy and allowed describing the observed movements of the luminaries with very high accuracy.
The most important breakthrough in understanding the true structure of the Solar System occurred in the XVI century, when the great Polish astronomer Nicolaus Copernicus developed the heliocentric system of the world[148].
It was based on the following statements: the Sun is at the center of the world, not the Earth; the spherical Earth rotates around its axis, and this rotation explains the apparent daily movement of all the luminaries; The Earth, like all other planets, revolves around the Sun in a circle, and this rotation explains the apparent movement of the Sun among the stars; all movements are represented as a combination of uniform circular movements; the apparent straight and backward movements of the planets do not belong to them, but to the Earth.
The sun in the heliocentric system has ceased to be considered a planet, as well as the Moon, which is a satellite of the Earth.
Soon 4 satellites of Jupiter were discovered, thanks to which the exclusive position of the Earth in the Solar system was abolished.
The theoretical description of the motion of the planets became possible after the discovery of the laws
Kepler at the beginning of the XVII century, and with the formulation of the laws of gravity, the quantitative description of the motion of the planets, their satellites and small bodies was put on a reliable basis.
In 1672, Giovanni Cassini and Jean Richet determined the distance to Mars, thanks to which the astronomical unit was expressed in terrestrial units of distance measurement.
The history of professional study of the composition of the Solar System began in 1610, when Galileo Galilei discovered the 4 largest satellites of Jupiter in his telescope[149].
This discovery was one of the proofs of the correctness of the heliocentric system.
In 1655, Christian Huygens discovered Titan — the largest moon of Saturn[150].
Until the end of the XVII century, Cassini discovered 4 more satellites of Saturn[151][152].
The XVIII century was marked by an important event in astronomy — for the first time, the previously unknown planet Uranus was discovered with the help of a telescope[153].
Soon, J. Herschel, the discoverer of a new planet, discovered 2 satellites of Uranus and 2 satellites of Saturn[154][155].
The XIX century began with a new astronomical discovery — the first planet — like object was discovered the asteroid Ceres, which was transferred to the rank of a dwarf planet in 2006.
And in 1846, the eighth planet was discovered — Neptune.
Neptune was discovered "on the tip of a pen", that is, it was first predicted theoretically, and then discovered through a telescope, and independently of each other in England and in France[156][157][158].
In 1930, Clyde Tombaugh (USA) discovered Pluto, named the ninth planet of the Solar system.
However, in 2006, Pluto lost its status as a planet and "became" a dwarf planet[159].
In the second half of the XX century, many large and very small moons of Jupiter, Saturn, Uranus, Neptune, Pluto were discovered[160][161][162][163].
The most significant role in this series of scientific discoveries was played by the Voyager missions — the American AMS.
At the turn of the XX—XXI centuries, a number of small bodies of the Solar system were discovered, including dwarf planets, plutino, as well as satellites of some of them and satellites of giant planets.
Instrumental and computational searches for trans Neptunian planets, including hypothetical ones, are continuing .
Colonization of the Solar system The practical significance of colonization is due to the need to ensure the normal existence and development of mankind.
Over time, the growth of the Earth's population, environmental and climatic changes can create a situation where the lack of a habitable territory will jeopardize the continued existence and development of the Earth's civilization.
Human activity can also lead to the need to settle other objects of the Solar System: the economic or geopolitical situation on the planet; a global catastrophe caused by the use of weapons of mass destruction; the depletion of the planet's natural resources, etc.
Within the framework of the idea of colonization of the Solar System, it is necessary to consider the so — called "terraforming" (Latin terra — earth and forma — species) - the transformation of the climatic conditions of a planet, satellite or other cosmic body to create or change the atmosphere, temperature and environmental conditions into a state suitable for the habitation of terrestrial animals and plants.
Today, this task is mainly of theoretical interest, but in the future it may also be developed in practice.
Mars and the Moon are primarily considered as the objects most suitable for colonization by colonists from Earth[164].
Other objects can also be transformed for people to live on them, but it will be much more difficult to do this due to both the conditions prevailing on these planets and a number of other factors (for example, the absence of a magnetic field, excessive remoteness or proximity to the Sun in the case of Mercury).
When colonizing and terraforming planets, it will be necessary to take into account the following: the magnitude of the acceleration of free fall[165], the amount of solar energy received[166], the presence of water[165], the level of radiation (radiation background) [167], the nature of the surface, the degree of threat of a collision of the planet with an asteroid and other small bodies of the Solar system.
Galactic orbit
The solar system is part of the Milky Way, a spiral galaxy with a diameter of about 30 thousand parsecs (or 100 thousand light — years) and consisting of approximately 200 billion stars[168].
The solar system is located near the plane of symmetry of the galactic disk (20-25 parsecs higher, that is, north of it), at a distance of about 8 thousand parsecs (27 thousand light years)[169] from the galactic center (almost at an equal distance from the center of the Galaxy and its edge), on the outskirts of the Orion arm [170] — one of the galactic arms of the Milky Way.
The sun rotates around the galactic center in an almost circular orbit with a speed of it travels about 254 km / s[171][172] (updated in 2009) and makes a complete revolution in about 230 million years[12].
This period of time is called the galactic year[12].
The solar apex (the direction of the Sun's path through interstellar space) is located in the constellation Hercules in the direction of the current position of the bright star Vega[173].
The structure of the Milky Way.
The location of the Solar system is indicated by a large yellow dot
In addition to the circular motion in orbit, the Solar System makes vertical oscillations relative to the galactic plane, crossing it every 30-35 million years and ending up in the northern, then in the southern galactic hemisphere[174][175][176].
The location of the Solar system in the galaxy probably affects the evolution of life on Earth.
Its orbit is almost circular; and the speed is approximately equal to the speed of the spiral arms, which means that it passes through them extremely rarely.
This gives the Earth long periods of interstellar stability for the development of life, since the spiral arms have a significant concentration of potentially dangerous supernovae[177].
The solar system is also located at a considerable distance from the crowded star filled surroundings of the galactic center.
Near the center, the gravitational effects of neighboring stars could disturb the objects of the Oort cloud and send many comets into the inner Solar system, causing collisions with catastrophic consequences for life on Earth.
The intense radiation of the galactic center could also affect the development of highly organized life[177].
Some scientists hypothesize that despite the favorable location of the Solar System, even during the last 35,000 years, life on Earth was exposed to supernovae, which could emit particles of radioactive dust and large comet like objects[178].
The immediate galactic neighborhood of the Solar System is known as the Local Interstellar Cloud.
This is a denser section of the rarefied gas region, a local bubble a cavity in the interstellar medium with a length of about 300 sv.
years, which has the shape of an hourglass.
The bubble is filled with high temperature plasma; this suggests that the bubble was formed as a result of the explosion of several recent supernovae[179].
There are relatively few stars within ten sv.
years (95 trillion km) from the Sun.
The nearest is the triple star system Alpha Centauri, at a distance of about 4.3 sv.
years.
Alpha Centauri A and B are a close binary system of stars similar in characteristics to the Sun, while the small red dwarf Alpha Centauri C (also known as Proxima Centauri) orbits this pair at a distance of 0.2 sv.
The next few years.
The next closest stars are the red dwarfs Barnard's star (5.9 sv. years), Wolf 359 (7.8 sv. years) and Lalande 21185 (8.3 sv.years).
The largest star within ten light — years is Sirius, a bright main sequence star with a mass of about two times the mass of the Sun and a companion, a white dwarf called Sirius B. Sirius is located at a distance of 8.6 sv.years.
The remaining systems within ten light years are the double system of red dwarfs Leuthen 726-8 (8.7 sv. years) and the single red dwarf Ross 154 (9.7 sv. years)[180].
The nearest brown dwarf system, Luman 16, is located at a distance of 6.59 light years.
The nearest single star similar to the Sun, Tau Ceti, is located at a distance of 11.9 sv.
years.
It has about 80 percent of the mass of the Sun, but only 60 percent of its brightness[181].
Nearest known
It has about 80 percent of the mass of the Sun, but only 60 percent of its brightness[181].
The nearest known exoplanet is located in the closest star system to us, Alpha Centauri, located at a distance of 4.3 sv.
years.
The only assumed planet in the system — Alpha Centauri B b, with a mass of about 1.1 Earth masses and a rotation period of only 3.2 days[182] - remains unconfirmed at the moment.
Diagram of the location of the Earth and the Solar system in the observable part of the Universe.
(Click here to view an alternative image.)
See also The movement of the Sun and planets along the celestial sphere Satellites in the Solar system Astronomical symbols The Titius Bode rule List of planet like objects List of Solar system objects by size
List of Solar System objects by size Phaethon (planet) History of Solar System Exploration Swedish Solar System
Notes ↑ Show compactly
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23. ↑ Harold F. Levison, Alessandro Morbidelli.
The formation of the Kuiper belt by the outward transport of bodies during Neptune’s migration (https://www n.oca.eu/morby/stuff/NA TURE.pdf) (англ.) (PDF) (2003).
Проверено 23 ноября 2009.
Архивировано из первоисточника 22 августа 2011 (http://ww w.webcitation.org/617F07bx3).
24. ↑ Harold F. Levison, Martin J Duncan.
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Space Physics Center: UCLA (2005).
Проверено 24 ноября 2009.
Архивировано из первоисточника 22 августа 2011 (http://ww w.webcitation.org/617GLJ6fS).
26. ↑ An Overview of the Solar System (http://nineplanets.org/o verview.html) (англ.).
The Nine Planets.
Проверено 2 декабря 2009.
Архивировано из первоисточника 22 августа 2011 (http://ww w.webcitation.org/617GOaHb6).
27. ↑ Amir Alexander.
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The Planetary Society (2006).
Проверено 2 декабря 2009.
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28. The Final IAU Resolution on the definition of «planet» ready for voting (http://www.iau.org/news/pressreleases/deta il/iau0602/) (англ.).
International Astronomical Union (24 August 2006).
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29. Dwarf Planets and their Systems (http://planetarynames.wr.u sgs.gov/Page/Planets#DwarfPlanets) (англ.).
Working Group for Planetary System Nomenclature (WGPSN).
U.S. Geological Survey (7 Nov 2008).
Проверено 5 декабря 2009.
Архивировано из первоисточника 17 августа 2011 (http://www.webc itation.org/610c8g3sc).
30. ↑ Ron Ekers.
IAU Planet Definition Committee (http://ww w.iau.org/public press/news/release/iau0601/newspaper/) (англ.) International Astronomical Union.
Проверено 5 декабря 2009.
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31. ↑ Plutoid chosen as name for Solar System objects like Pluto (http://www.iau.org/news/pressreleases/detail/iau080 4/) (англ.).
International Astronomical Union (11 June 2008, Paris).
Проверено 5 декабря 2009.
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32. M. Podolak; J. I. Podolak; M. S. Marley.
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33. M. Podolak; A. Weizman; M. Marley.
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34. ↑ Michael Zellik.
Astronomy: The Evolving Universe.
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(англ.) 35. ↑ Kevin W. Placxo;
