Information about the solar system

The solar system includes the sun, four inner planets similar to the earth, an asteroid belt composed of many small rocks, and four giant outer planets filled with gas and frozen small rocks, which is called the second small celestial body area of the Kuiper Belt. In addition to the Kuiper Belt, there are ecliptic discrete disks and solar circles, as well as Oort clouds that still belong to the hypothesis.

According to the distance from the sun, the order of planets is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Six of the eight stars are surrounded by natural satellites. These stars are traditionally regarded as the moon, because the satellites of the earth are called the moon. The outer planet is surrounded by a planetary ring composed of dust and many small particles. Except the earth, the planets visible to the naked eye are all named after five acts, while in the west, they are all named after the immortals in Greek and Roman mythology. These three dwarf planets are Pluto, one of the largest celestial bodies in the Kuiper Belt, Ceres, the largest celestial body in the asteroid belt, and Neptune, a discrete celestial body belonging to the ecliptic.

Overview and dynamic observation

The orbit of celestial bodies in the solar system The protagonist of the solar system is the central sun. It is a main sequence star with a spectral classification of G2V, which has 99.86% of the known mass of the solar system and is dominated by gravity. Jupiter and Saturn, the two largest planets in the solar system, account for more than 90% of the remaining mass. At present, they still belong to the hypothetical Oort cloud, and how much mass percentage they will occupy is still unknown.

The orbits of the main celestial bodies in the solar system are all near the orbital plane (ecliptic) of the earth around the sun. Planets are very close to the ecliptic, while comets and celestial bodies in the Kuiper Belt usually have obvious inclination angles.

Looking down at the solar system from the north, all the planets and most other celestial bodies revolve around the sun in a counterclockwise (right-handed) direction. There are some exceptions, such as Halley's comet.

Celestial bodies moving around the sun obey Kepler's law of planetary motion, and their orbits all take the sun as a focus of the ellipse. The closer they are to the sun, the faster their speed will be. The orbits of planets are almost circular, but the orbits of many comets, asteroids and celestial bodies in the Kuiper Belt are highly elliptical.

In such a vast space, the distance between the orbits of the solar system has many expressions. In fact, the farther away from the sun, the farther away from the planet or the ring belt, with a few exceptions. For example, Venus is about 0.33 AU from Mercury, Saturn is about 4.3 AU from Jupiter, and Neptune is about 0/0.5 AU from Uranus/kloc. Some relationships try to explain the interaction between these orbital distance changes, but such a theory has never been confirmed.

Formation and evolution

The protoplanetary disc written by the artist

It is believed that the formation of the solar system should be based on the nebula hypothesis, which was first put forward by Kant in 1755 and Laplace in 1796. According to this theory, the solar system was formed by the collapse of a huge molecular cloud 4.6 billion years ago. This nebula was originally several light-years in size, and several stars were born at the same time. The study of elements dating back to ancient meteorites shows that only the heart part of supernova explosion can produce these elements, so the cluster containing the sun must be near the supernova remnant. It may be that the shock wave generated by the supernova explosion increased the density of the nebula near the sun, which enabled gravity to overcome the expansion pressure of the internal gas and lead to collapse, thus triggering the birth of the sun.

The area identified as the Taiyang Yuan Nebula is where the future solar system will form. The diameter is estimated to be 7,000 to 20,000 astronomical units, and the mass is only a little larger than that of the sun (0. 1 to 0.00 1 solar mass). When the nebula begins to collapse, the law of conservation of angular momentum accelerates its rotation speed and the frequency of internal atoms colliding with each other increases. Its central area concentrates most of the mass, and the temperature is hotter than the surrounding disks. When gravity, air pressure, magnetic field and rotation act on the shrinking nebula, it begins to flatten into a rotating protoplanetary disk with a diameter of about 200 astronomical units and a hot and dense protostar at the center.

It is believed that the mass of the young T-star in Taurus is very similar to that of the sun in the pre-fusion stage, which indicates that there is always a disk of protoplanetary material in the formation stage. These disks can extend to hundreds of astronomical units, and the hottest part can reach thousands of K.

After 100 million years, in the center of the collapsed nebula, the pressure and density will be large enough to make the hydrogen of the primitive sun start thermal fusion, which will increase to hydrostatic equilibrium, so that the thermal energy will be enough to resist the contraction energy of gravity. Only then will the sun become a real star.

It is believed that through accretion, all kinds of planets will be born from the remaining gas and dust in the cloud gas (solar nebula):

When dust particles are still around the central protostar, the planet has begun to grow;

Then, through direct contact, they gather into a cluster with a diameter of 1 to 10 km;

Then through collision, a larger individual is formed and becomes an planetesimal with a diameter of about 5 kilometers;

In the next few million years, it will continue to grow at the rate of 15cm per year through further collisions.

On the inner side of the solar system, because the temperature is too high, the volatile molecules such as water and methane cannot condense, so the planetesimals formed are relatively small (only accounting for 0.6% of the mass of the disk), and the main components are silicates and metals with high melting points. These rocky celestial bodies eventually became terrestrial planets. The planetesimals farther away, influenced by Jupiter's gravity, could not condense into protoplanets, but became the asteroid belt we see now.

At a farther distance, outside the freezing line, volatile substances can also freeze into solids, forming giant gas giants such as Jupiter and Saturn. Uranus and Neptune are called ice giants because their cores are mainly ice (hydride).

Once the young sun begins to generate energy, the solar wind will blow the material in the original planetary disk into interplanetary space, thus ending the growth of the planet. The star wind of the young Taurus T star is much stronger than that of the stable old star.

According to astronomers' speculation, the current solar system will remain until the sun leaves the main sequence. Because the sun uses its internal hydrogen as fuel, in order to use the remaining fuel, the sun will become hotter and hotter, so the burning speed will be faster and faster. This causes the sun to continue to brighten, and the brightening speed is about11million years.

After about 7.6 billion years, the temperature of the sun's inner core will be enough to melt the hydrogen in the outer layer, which will cause the sun to expand to 260 times its current radius and become a red giant. At this time, due to the expansion of volume and surface area, the total luminosity of the sun increases, but the surface temperature decreases and the luminosity per unit area darkens.

Then, the outer layer of the sun was gradually thrown away, and finally the core was exposed as a white dwarf, a kind of extremely dense celestial body, only the size of the earth but only half the mass of Taiyang Yuan.

[Edit this paragraph] Structure and composition

The solar system is a system composed of celestial bodies constrained by the sun's gravity, and it is a small celestial body system in the universe.

The structure of the solar system can be roughly divided into five parts:

sun

The sun is the parent star of the solar system and the most important member. It has enough mass, so that the internal pressure and density are enough to suppress and bear the huge energy generated by nuclear fusion, so that the energy can stably enter space in the form of radiation, such as visible light. The position of the sun on the Herro diagram

The sun is classified as a medium-sized yellow dwarf, but such a name is easily misunderstood. In fact, in our galaxy, the sun is quite big and bright. According to the corresponding relationship between surface temperature and brightness of Hertzog diagram, the stars are classified. Usually, stars with high temperature will be brighter, and stars following this rule will be located in the so-called main sequence zone, with the sun at the center of this zone. However, there are not many stars bigger and brighter than the sun, but there are many darker and colder stars.

The sun is in the heyday of star evolution, and the core nuclear fusion hydrogen has not been used up. The brightness of the sun will still increase day by day, and the early brightness is only 75% now.

By calculating the ratio of hydrogen to helium in the sun, it is considered that the sun has completed half of its life cycle. After about 5 billion years, the sun will leave the main sequence belt and become a bigger and brighter red giant with a lower surface temperature. By then, it will be thousands of times brighter than it is now.

The sun is the first group of stars born in the late evolution of the universe. It has more metals heavier than hydrogen and helium than the stars in the second group (this is an astronomical saying: all atoms with more atoms than helium are metals. )。 Elements heavier than hydrogen and helium are formed in the core of a star and must be released into space by supernova explosion. In other words, these heavy elements only exist in the universe after the death of the first generation of stars. The oldest stars have only a small amount of metal, and later stars have more metal. High metal content is considered to be the key to the development of planetary systems by solar energy, because planets are formed by the accumulation of metal substances.

Interplanetary matter

In addition to light, the sun constantly sends out a stream of electrons (plasma), which is called the solar wind. The speed of this particle flow is 6.5438+0.5 million kilometers per hour, forming a thin atmosphere (solar circle) in the solar system, with a range of at least 654.38+0.000 astronomical units (heliopause), which is what we call interplanetary matter. The sunspot period of the sun (1 1 year) and the interference caused by frequent flash flames and coronal mass ejections in the solar circle have produced space climate. The solar current sheet produced by the magnetic field rotating with the rotation of the sun in interplanetary matter is the largest structure in the solar system.

The earth's magnetic field protects the earth's atmosphere from the solar wind. Mercury and Venus have no magnetic fields, and the solar wind gradually draws their atmospheres into space. Near the magnetic poles near the earth, such as the South Pole and the North Pole, you can see the aurora produced by the interaction between the solar wind and the earth's magnetic field.

Cosmic rays come from outside the solar system, and the solar circle shields the solar system. The planet's magnetic field also provides some protection for the planet itself. The density of cosmic rays in interstellar matter is related to the intensity change of solar magnetic field cycle, so how much cosmic rays change in the solar system is still unknown.

Interplanetary matter gathers into cosmic dust in at least two disk-shaped regions. The first area is the ecliptic dust cloud, which is located in the inner solar system and is the cause of zodiacal light. They may be caused by the collision between celestial bodies and planets in the asteroid belt. The second region extends about 10-40 astronomical units, which may be caused by similar collisions between celestial bodies in the Kuiper Belt.

inner solar system

Traditionally, the inner solar system is the name of the region of terrestrial planets and asteroid belts, which is mainly composed of silicates and metals. This area is squeezed very close to the sun, and the radius is shorter than the distance between Jupiter and Saturn.

Inner planet. All inner planets

The four inner planets or terrestrial planets are characterized by high density, composed of rocks, few or no satellites, and no ring system. They are composed of high melting point minerals such as silicate minerals, the crust is solid surface and semi-liquid mantle, and the metal core is composed of iron and nickel. Three of the four stars (Venus, Earth and Mars) have rich atmospheres, and they all have the surface features of impact craters and geological structures (graben and volcano, etc.). ) The inner planets are easily confused with the inner planets (Mercury and Venus) which are closer to the sun than the Earth. Planets run on a plane and face in one direction.

mercury

Mercury (0.4 astronomical unit) is the closest planet to the sun and the smallest planet (0.055 earth mass). It has no natural satellites, and the only known geological features are folded ridges that may have been produced during early history and contraction, except for impact craters. Mercury, including gas atoms bombarded by the solar wind, has only a negligible atmosphere. At present, it is impossible to explain the relatively huge iron core and thin mantle. The hypothesis includes that a huge impact peeled off its shell, and the solar energy at a young age inhibited the growth of the shell.

Venus

Venus (0.7 astronomical unit) is similar in size to the Earth (0.86 earth mass), and it also has a thick silicate mantle surrounding the core like the Earth, and there is also strong evidence of atmospheric and internal geological activities. However, its atmospheric density is 90 times higher than that of the earth, it is very dry, and there are no natural satellites. It is a hot planet with a surface temperature of over 400℃, which is probably caused by a large amount of greenhouse gases in the atmosphere. There is no clear evidence that Venus' geological activities are still going on, but the atmosphere without magnetic field protection should be exhausted, so it is considered that Venus' atmosphere is supplemented by volcanic eruption.

earth

The earth (1 astronomical unit) is the largest and densest planet among the inner planets, and it is also a living planet whose geological activities are still continuing. Among terrestrial planets, it also has a unique hydrosphere and observed plate structure. The earth's atmosphere is completely different from other planets, and it has been transformed into free oxygen containing 2 1% by the creatures here. It has only one satellite, the moon; The moon is also the only big satellite among terrestrial planets. It takes about 365 days for the earth (sun) to make a revolution, and it takes about 1 day for the earth to make a revolution. The sun doesn't always point directly at the equator, because the earth tilts slightly when it rotates around the sun. )

launch

Mars (1.5 astronomical unit) is smaller than Earth and Venus (0. 17 Earth mass), and has only a thin atmosphere dominated by carbon dioxide. Its surface, such as Mount Olympus, has dense and huge volcanoes, and Mariner Canyon has deep graben, which shows that there was still strong geological activity not long ago. Mars has two natural small satellites, demos and faubus, which may be captured asteroids.

asteroid belt

Asteroid main belt and Trojan asteroid are the most important members of small bodies in the solar system, which are mainly composed of rocks and non-volatile substances.

The main asteroid belt lies between the orbits of Mars and Jupiter, 2.3 to 3.3 astronomical units away from the sun. They are considered to be residual materials disturbed by Jupiter's gravity during the formation of the solar system.

Asteroids range in size from hundreds of kilometers to microns. All asteroids except Ceres, the largest, are classified as small objects in the solar system, but several asteroids such as Vesta and blade master may be reclassified as dwarf planets if they can be confirmed to be in hydrostatic equilibrium.

There are tens of thousands, possibly millions of small celestial bodies with a diameter of more than one kilometer in the asteroid belt. Nevertheless, the total mass of the asteroid belt is still impossible to reach one thousandth of the mass of the earth. The members of the asteroid main belt are still sparse, so so far no spacecraft has had an accident when crossing.

Small celestial bodies with a diameter of 10 to 10-4 meters are called meteoroids.

ceres

Ceres (2.77 astronomical units) is the largest celestial body in the main belt and the only dwarf planet in the main belt. Its diameter is close to 1000 km, so its own gravity is enough to make it a sphere. It was considered a planet when it was discovered in the early19th century, and was reclassified as an asteroid in the1850s because more small objects were discovered. In 2006, it was reclassified as a dwarf planet again.

Asteroid family

Asteroids in the main belt can be divided into several asteroid groups and asteroid families according to orbital elements. Asteroid satellites are small celestial bodies orbiting larger asteroids, and their identification is not as clear as that of satellites orbiting planets, because some satellites are almost as big as their mother bodies.

There are also comets in the main belt, which may be the main source of water on the earth.

The position of the Trouvat asteroid is at the L4 or L5 point of Jupiter (the unstable gravitational equilibrium point before and after the planetary orbit), but the name "Trouvat" is also used for the small celestial bodies located at the Lagrangian point in the orbits of other planets or satellites. The Hilda family is an asteroid family, and its orbital period oscillates with Jupiter's 2: 3 * *. When Jupiter orbits the sun twice, this group of asteroids will orbit the sun three times.

The inner solar system also contains many "naughty" asteroids and dust particles, many of which will cross the orbit of the inner planet.

Intermediate solar system

The central part of the solar system is home to gas giant planets and their planet-sized satellites, and many short-period comets, including Centaurs, are also in this area. This area has no traditional name and is occasionally classified as "the outer solar system", although the outer solar system usually refers to the area outside Neptune. The solids in this area are mainly composed of "ice" (water, ammonia and methane), which is different from the inner solar system dominated by rocks.

superior planet

All the exoplanets are outside the four planets, which are also called woody planets and contain 99% of the known mass around the sun. The atmospheres of Jupiter and Saturn are rich in hydrogen and helium, while those of Uranus and Neptune are rich in "ice", such as water, ammonia and methane. Some astronomers think they should be classified into another category, called "Uranus family" or "ice giant". All four gas giants have planetary rings, but only Saturn's rings can be easily observed from the earth. The name "exoplanet" is easily confused with "exoplanet". In fact, it refers to planets outside the earth's orbit, in addition to Mars.

Jupiter

Jupiter (5.2 astronomical units) is mainly composed of hydrogen and helium, and its mass is 365,438+08 times that of the earth and 2.5 times that of other planets combined. Jupiter's abundant internal heat leads to some almost permanent features in its atmosphere, such as cloud bands and great red spots. Jupiter has discovered 63 satellites, the largest four of which, Ganymede, Calisto, Eo and Europa, show similar characteristics to terrestrial planets, such as volcanism and internal heat. Ganymede is bigger than Mercury and the largest satellite in the solar system.

Saturn

Saturn (9.5 astronomical units) is famous for its obvious ring system, which is very similar to Jupiter, such as the structure of the atmosphere. Saturn is not very big, its mass is only 95 times that of the earth. It has 60 known satellites, Titan and Enceladus, and huge ice and volcanoes, showing signs of geological activity. Titan is bigger than mercury and is the only satellite in the solar system that really has an atmosphere.

Uranus

Uranus (19.6 astronomical unit) is the lightest exoplanet, and its mass is 14 times that of Earth. Its axis of rotation is inclined at 90 degrees to the ecliptic, so it lies horizontally around the sun, which is very unique among the planets. Among gas giants, its core temperature is the lowest, and it only radiates very little heat into space. Uranus has 27 known satellites, the largest of which are Titan, oberon, Ambarel, Ariel and Miranda.

Neptune

Although Neptune (30 astronomical units) looks smaller than Uranus, its high density still makes its mass 17 times that of the earth. Although it radiates more heat, it is far less than Jupiter and Saturn. Neptune is known to have 13 satellites, and the largest triton is still active in geological activities. Geysers erupt liquid nitrogen, and it is also the only retrograde satellite in the solar system. In the orbit of Neptune, there are some asteroids with the orbit of 1: 1, which form the Trojan Group of Neptune.

comet

Comets are small celestial bodies in the solar system, usually only a few kilometers in diameter, and are mainly composed of volatile ice. Their orbits have high eccentricity, perihelion is generally inside the orbit of the inner planet, while apohelion is outside Pluto. When a comet enters the inner solar system, its proximity to the sun will lead to the sublimation and ionization of substances on its ice surface, resulting in coma and dragging out a tail composed of gas and dust particles visible to the naked eye.

Short-period comets are comets with orbital periods shorter than 200 years, and long-period comets have orbital periods as long as thousands of years. Short-period comets, such as Halley's Comet, are thought to come from the Kuiper Belt; Long-period comets, such as Comet Hale Popper, are thought to have originated from Oort Cloud. There are many comets, such as Cruz family comets, which may have originated from a collapsed matrix. Some comets with hyperbolic orbits may come from outside the solar system, but it is difficult to accurately measure these orbits. Comets whose volatile substances are dispersed by solar heat are usually classified as asteroids.

Centaur

Centaurs are scattered in the range of 9 to 30 astronomical units, that is, they orbit Jupiter and Neptune and are ice-based objects similar to comets. The largest celestial body known to centaurs is 10 199 Chariklo, with a diameter of 200 to 250 kilometers. The first one was discovered in Long Xing in 2060. It was classified as a comet because it would produce a comet-like coma when it approached the sun. Some astronomers classify Centaur as a discrete celestial body inside the Kuiper Belt and regard it as a continuation of the external discrete disk.

Outer Neptune region

The area outside Neptune, usually called the outer solar system or the outer Neptune area, is still a vast unexplored space. This area seems to be the world of small celestial bodies in the solar system (the largest diameter is less than one-fifth of that of the earth and the mass is much smaller than that of the moon), which is mainly composed of rocks and ice.

Kuiper belt

The original form of the Kuiper Belt is considered to be an annular belt composed of debris and debris similar in size to asteroids, but mainly composed of ice, which spreads at a distance of 30 to 50 astronomical units from the sun. This area is considered to be the source of short-period comets, such as Halley's Comet. It is mainly composed of small celestial bodies in the solar system, but many of the largest celestial bodies in the Kuiper Belt, such as Chuangshenxing, Varuna, 2003 EL6 1, 2005 FY9 and Elkus, may be classified as dwarf planets. It is estimated that there are more than 100000 celestial bodies with a diameter of more than 50 kilometers in the Kuiper Belt, but the total mass may be only one tenth or even one percent of the mass of the earth. Many celestial bodies in the Kuiper Belt have more than two satellites, and most of their orbits are not on the ecliptic plane.

Kuiper belt can be roughly divided into * * vibration belt and traditional belt. * * The vibration band consists of celestial bodies that have a * * vibration relationship with Neptune's orbit (Neptune orbits the sun three times and twice, or Neptune orbits the sun twice and only once). In fact, Neptune itself is a member of the * * * vibration belt. Traditional members are celestial bodies that do not vibrate with Neptune and are scattered in the range of 39.4 to 47.7 astronomical units. The traditional Kuiper Belt celestial bodies are classified as QB 1 celestial bodies with the name 1992 QB 1, which is one of the first three celestial bodies discovered.

Pluto and Ka Rong.

Pluto and its three known satellites (with an average distance of 39 astronomical units) are dwarf planets and one of the largest known celestial bodies in the Kuiper Belt. When 1930 was discovered, it was considered the ninth planet, and it was not reclassified as a dwarf planet until 2006. Pluto's orbit is inclined to the ecliptic plane 17 degrees, and its distance from the sun is 29.7 astronomical units at perihelion (within Neptune's orbit) and 49.5 astronomical units at aphelion.

At present, it is uncertain whether Ka Rong, the satellite of Pluto, should be classified as a satellite or a dwarf planet, because the orbital centers of mass of Pluto and Ka Rong are not below the surface of either one, forming a Pluto-Ka Rong binary system. Two other small satellites, the Knicks and Xu Dela, revolve around Pluto and Ka Rong.

Pluto vibrates 3:2 * * with Neptune on the * * * vibration band (Pluto orbits the sun twice and Neptune orbits the sun three times). The objects with such orbits in the Kuiper Belt are collectively called ghost-like objects.

Dispersed disk-shaped object

The discrete disks overlap with the Kuiper Belt, but extend outward to further space. The celestial bodies in the discrete disk should be in the early process of the formation of the solar system, because the gravitational disturbance caused by Neptune's outward migration was thrown into the fluctuating orbit from the Kuiper Belt. The perihelion of most ecliptic discrete celestial bodies is in the Kuiper Belt, but the apohelion can be as far as 150 astronomical unit. The inclination angle of the track to the ecliptic plane is also very large, and some of them are even perpendicular to the ecliptic plane. Some astronomers think that the ecliptic discrete celestial bodies should be another part of the Kuiper Belt, and they should be called "Kuiper Belt discrete celestial bodies".

In addition, another purpose of studying celestial systems similar to the solar system is to explore whether there is life on other planets.

The solar system is a system composed of celestial bodies constrained by the sun's gravity, and its maximum range can extend to about 1 light-year. The main members of the solar system are: the sun (star), nine planets (including the earth), countless asteroids, many satellites (including the moon), comets, meteoroids, and a lot of dust and thin gaseous substances. In the solar system, the mass of the sun accounts for 99.8% of the total mass of the solar system, and the sum of the masses of other celestial bodies is less than 0.2% of the sun. The sun is the central celestial body, and its gravity controls the whole solar system, making other celestial bodies revolve around the sun. The nine planets in the solar system (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto) all revolve around the sun in the same direction in nearly circular orbits near the same plane.

distance

(AU)

radius

(Earth)

quality

(Earth)

Path inclination

(degree)

railway

weird

slanting

density

(g/cm3)

Sun 0109 332 800-1.45438+00

Mercury 0.39 0.38 0.057 0.2056 0.15.43

Venus 0.72 0.95 0.89 3.394 0.0068177.45.25

Earth1.01.001.000 0.0167 23.45 5.52

Mars1.5 0.53 0.11.1.850 0.0934 25.193.95

Jupiter 5.211.03181.308 0.0483 3.121.33

Saturn 9.5 9.5 95 2.488 0.0560 26.73 0.69

Uranus19.24.017 0.774 0.861.29.

Neptune 30.1.3.91.774 0.0097 29.561.64

Pluto 39.50.180.00217.150.248219.62.03.