Introduce the composition and members of the solar system.

The solar system is the star system where we are now. It is a collection of all celestial bodies with the sun as the center and constrained by the sun's gravity: the field of the solar system includes the sun, and four inner planets like the Earth, Mercury, Venus, Earth and Mars; An asteroid belt composed of many small rocks, four giant gas-filled exoplanets Jupiter, Saturn, Uranus and Neptune; The second small celestial body area is called the Kuiper Belt, which is full of frozen rocks. In addition to the Kuiper Belt, there are ecliptic discrete disks, solar circles and Oort clouds, which are still hypothetical. The sun is the parent star of the solar system, the only shining star in 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. 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.

Mercury (0.4 astronomical unit) is the smallest planet closest to the sun (0.055 earth mass), with a daily average distance of 579 10000 km(0.38 AU), a diameter of 4878 km, a mass of 3.30e23 kg, a density of 5.43 gm/cm, a gravity of 0.376 G, and a revolution of 87.97 earth days. 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 (0.7 astronomical unit) is similar in size to the Earth (0.86 earth mass), with a daily average distance of 108200000 km(0.72 AU), a diameter of 12 103.6 km, a mass of 4.869e24 kg and a density of 5.24 gm/cm. 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.

The daily average distance of the earth (1 astronomical unit) 149600000 km( 1 AU), diameter 12756.3 km, mass 5.976e24 kg, density 5.52 gm/cm, gravity1g. Its period of revolution is 365.2422 Earth days and its rotation period is 0.9973 Earth days. It is the largest and densest planet among the inner planets, and the only one with ongoing geological activities and life (so far, scientists have not explored other creatures from space). 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. The earth (sun) makes one revolution for about 365 days, and the earth rotates once for about 1 day. The sun doesn't always point directly at the equator, because the earth tilts slightly when it rotates around the sun.

Mars (1.5 astronomical unit) has a daily average distance of 227,940,000 km (1.52 au), a diameter of 6794 km, a density of 6.42 19e23 kg, a gravity of 3.94 gm/cm and a revolution of 686.98 earth days. 1.026 The rotation of Earth Day is smaller than that of Earth and Venus (0. 1.7 Earth mass), and there is 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, indicating that there was still strong geological activity not long ago. Mars has two natural small satellites, demos and faubus, which may be captured asteroids.

The asteroid belt is mainly composed of rocks and non-volatile substances. They are located between the orbits of Mars and Jupiter, 2.3 to 3.3 astronomical units away from the sun, and are considered to be the 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.

Ceres (2.77 astronomical unit) 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.

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.

Jupiter (5.2 astronomical units) has a daily average distance of 778330000 km(5.20 AU), a diameter of142,984 km, a mass of 1.900e27 kg, a density of 1.3 1 GM/cm, and a gravity revolution of 2.34. The Earth Day with a rotation of 0.4 14 is mainly composed of hydrogen and helium, and its mass is 3 18 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. There are 63 satellites discovered by Jupiter, and the largest four, Ganymede, Calisto, Eo and Europa, show the characteristics similar to terrestrial planets, such as the internal heat of volcanic activity. Ganymede is bigger than Mercury and the largest satellite in the solar system.

Saturn (9.5 astronomical units) has a daily average distance of 1429400000 km(9.54 AU), a diameter of 120536 km (equator), a mass of 5.688e26 kg, a density of 0.69 gm/cm and a gravity of1./kloc-0. 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 icebergs, 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 (19.6 astronomical unit) has a daily average distance of 2870990000 km (19.218au), a diameter of 5120 km (equator), a mass of 8.686e25 kg and a density of/. 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 (30 astronomical units) has a daily average distance of 4504000000 km(30.06 AU), an equal diameter of 49528km, a mass of 1.0247e26 kg, a density of 1.64 GM/cm, and a gravity of1. Rotation period: 15 hours, 57 minutes and 59 seconds. Although it looks smaller than Uranus, its higher 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.

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.

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 500 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 are not sure whether Ka Rong should be classified as a satellite or a dwarf planet at present, 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 microsatellites, Nick and Xu Dela, revolve around Pluto and Ka Rong on Mars (136 199 Eris) (with an average distance of 68 astronomical units), also known as Zener, which is the largest known zodiacal discrete celestial body, and has triggered a debate about what a planet is. Its diameter is at least 15% larger than Pluto, and it is estimated to be 2400 kilometers (1500 miles), making it the largest dwarf planet known. Mars has a satellite called Triton I, and its orbit is as eccentric as Pluto. The distance of perihelion is 38.2 astronomical units (about the average distance from Pluto to the sun), and the apohelion reaches 97.6 astronomical units, and its inclination with the ecliptic plane is also very large.

Oort Cloud is a hypothetical spherical cloud around the solar system, which is covered by many inactive comets. It is about 50,000 to 65,438+000,000 astronomical units from the sun, which is almost equal to one light year, that is, a quarter of the distance from the sun to proxima centauri. Theoretically, Oort Cloud has trillions of icy objects and huge mass, and it orbits the solar system at a distance of about 5,000 astronomical units, up to10,000 astronomical units, which is considered as the source of long-period comets. People think they are comets thrown there from the inner solar system by the gravity of outer planets. Objects in the Oort cloud move very slowly and are affected by some unusual circumstances, such as collisions, or gravity passing through celestial bodies, or galactic tides.

Sedna is a huge red ghostly celestial body with perihelion of 76 astronomical units and apohelion of 928 astronomical units. It takes 65,438+0 to complete a huge orbit with high ellipticity in 2050. Michael brown discovered this celestial body in 2003, because its perihelion is too far away to be affected by Neptune's migration, so he thinks it is not a member of the discrete disk or the Kuiper Belt. He and other astronomers think it belongs to a new classification. Also belonging to this new group are perihelion of 45 astronomical units, apohelion of 4 15 astronomical units, orbital period of 2000 CR 105 of 3420, perihelion of 2 1 astronomical units, apohelion of 1000 astronomical units and orbital period of 60. Brown named this ethnic group "Naiot Cloud". Although it is far from the sun, it is still very close, which may be formed through a similar process. Sedna's shape has been confirmed, very much like a dwarf planet.

The boundary of the solar system There are many unknown things in our solar system. Considering the nearby stars, it is estimated that the solar gravity can control the range of 2 light years (125000 astronomical units). The Oort cloud may not extend more than 50,000 astronomical units. Although Sedna was found between the Kuiper Belt and Oort Cloud, there are still tens of thousands of astronomical unit radius areas that have not been detected. The area between mercury and the sun is still under study. It is still possible to find something in the unknown area of the solar system.

At present, there are five dwarf planets: Ceres, Pluto, Eris, Io and Europa.

I hope I can help you. Good luck.