1. Mercury is the innermost and smallest of the eight planets in the solar system and the closest planet to the sun. China, known as Chen Xing, has the largest orbital eccentricity among the eight planets. It orbits the sun once every 87.968 Earth Days and rotates once every 2.0 1 for 3 times.
Among the planets in the solar system, Mercury has the smallest orbital inclination. The perihelion precession of Mercury orbit is 43 arc seconds more than predicted by Newtonian mechanics every century. It was not until the 20th century that Einstein's general theory of relativity explained this phenomenon.
Mercury is a planet similar to the earth. Because it is close to the sun, it will only appear as a morning star in the morning or as a dim star at dusk. Mercury is usually invisible in the sun unless there is a solar eclipse.
2. Venus, one of the eight planets in the solar system, is the second in distance from the sun, with a distance of 0.725 astronomical unit. It is the closest planet to the earth (Mars is sometimes closer). The ancient Romans called it Venus, China called it Chang Geng, Qi Ming, Taibai or Taibai Venus, and Aphrodite in ancient Greek mythology. Period of revolution is 224.7438+0 Earth Day.
The brightness in the night sky is second only to the moon, and Venus will reach its maximum brightness before sunrise or after sunset. It appears in the eastern sky in the morning and is called "Qi Ming". Dusk is in the west of the sky, called Chang Gung.
2065438+September 2, 2008, Tianyu will stage a beautiful astronomical phenomenon of "merging" Venus and Jiaokou Star. At that time, the two bright stars will be in close contact and stage a romantic "star attraction" for the public.
3. The earth is one of the eight planets in the solar system, ranking the third in the order from near to far from the sun, and the earth-like planet with the largest diameter, mass and density in the solar system, with a distance of 65.438+0.5 billion kilometers from the sun. The earth rotates from west to east and revolves around the sun at the same time. At present, there is a natural satellite-the moon, which forms a celestial system-the earth-moon system. It originated from the primitive solar nebula 4.6 billion years ago.
The equatorial radius of the earth is 6378. 137 km, the polar radius is 6356.752 km, the average radius is about 637 1 km, and the equatorial circumference is about 40076 km. It is an irregular oval sphere with slightly flat poles and slightly bulging equator. The surface area of the earth is 5 1 100 million square kilometers, of which 7 1% is ocean and 29% is land. Seen from space, the earth looks blue.
There are core, mantle and shell structures inside the earth, and hydrosphere, atmosphere and magnetic field outside the earth. The earth is the only known celestial body with life in the universe at present, and it is the home of millions of creatures, including human beings.
Mars is one of the eight planets in the solar system and the fourth planet in the solar system from the inside out. It is a terrestrial planet, with a diameter of about 53% of the Earth's and a mass of 1 1% of the Earth's. Due to the axial tilt, the rotation period is similar to that of the earth, and one circle is about twice that of the earth. The orange appearance is the surface hematite (iron oxide). In China's ancient books, Mars was called "the twinkling star", while in ancient western countries (ancient Rome) it was called "the star in the myth of Mars".
Mars is basically a desert planet, its surface is covered with sand dunes and gravel, and there is no stable liquid water body (2065438+September 28th, 2005, NASA announced that there is a small amount of water on Mars.
According to Agence France-Presse reported on July 25th, 20 18, researchers from the European Space Agency (ESA) said that the first liquid groundwater lake was discovered on Mars. The atmosphere dominated by carbon dioxide is thin and cold, and dust is suspended in it, and dust storms often occur every year. The polar caps composed of water ice and dry ice at the poles of Mars will fluctuate with the seasons.
Compared with the earth, the geological activities of Mars are relatively inactive. Most of the surface landforms were formed in ancient times, with dense craters, volcanoes and canyons, including Mount Olympus, the highest peak in the solar system, and Mariner Canyon, the largest canyon. Another unique topographical feature is the obvious difference between the northern and southern hemispheres: the southern part is an ancient highland covered with craters, while the northern part is a younger plain.
Mars has two natural satellites: Phobos and Phobos, which are irregular in shape and may be captured asteroids. On earth, Mars is visible to the naked eye, with the highest brightness reaching -2.9. Among the eight planets, it is darker than Jupiter and Venus. On September 28th, 20 15, NASA announced the existence of running water on Mars.
Jupiter is the largest and fastest rotating planet among the eight planets in the solar system, and the fifth planet from the inside out. Its mass is one thousandth of that of the sun and 2.5 times that of the other seven planets in the solar system combined. Jupiter, Saturn, Uranus and Neptune are all gaseous planets, so they are also collectively called woody planets (Jupiter and Saturn are collectively called gaseous giants).
Jupiter is a gas giant planet, accounting for 70% of all planets in the solar system. The main component is hydrogen, followed by helium, accounting for 25% of the total mass. The core contains other heavier elements. What humans usually see is the cloud top in the atmosphere, and the air pressure is slightly higher than 1 atmospheric pressure.
Jupiter is a flat sphere (with a slight but obvious bulge near the equator) because it rotates very fast. The outer atmosphere is obviously divided into several regions according to latitude, and turbulence and storms are easy to appear at the edge of regional connection. The most prominent example is the Great Red Spot, which was first discovered by telescope in the17th century. Surrounding this planet is a loose planetary ring system and a powerful magnetosphere. Jupiter has at least 79 moons.
2065438+In February 2008, NASA released a set of images of Jupiter's South Pole taken by Juno satellite. The striking blue vortex is twisted, changing into gorgeous patterns and creating amazing wonders.
In 20 18, astronomers discovered 12 new Jupiter satellites, bringing the number of known satellites of this gas giant planet to 79. When scientists observed the objects in the Kuiper Belt from a further distance, they photographed them. The two newly added satellites are named "S/20/KOOC-0/6 J/KOOC-0/"and "S/20/KOOC-0/7 J/KOOC-0/",which are 2/KOOC-0/10,000 km away from Jupiter and 24 million km away from Jupiter respectively.
6. Saturn, one of the eight planets in the solar system, ranks sixth in distance (from near to far) from the sun, and its mass is second only to Jupiter. Like Jupiter, it belongs to a gas giant planet. In ancient Europe (ancient Greece), Saturn was called Cronian, and in ancient China, it was also called revitalization or filling star.
Saturn is mainly composed of hydrogen, with a small amount of helium and trace elements. Its core includes rocks and ice, and its periphery is surrounded by several layers of metallic hydrogen and gas. The outermost atmosphere is usually flat in appearance, although it sometimes has long-standing characteristics. Saturn's wind speed is as high as 1800 km/h, which is obviously faster than Jupiter's.
Saturn's planetary magnetic field strength is between the earth and the stronger Jupiter.
Saturn has a remarkable planetary ring (which can be directly observed through a telescope), and its main components are ice particles and less rock fragments and dust. Saturn has 62 confirmed moons. Among them, Titan is the largest satellite in Saturn system and the second largest satellite in the solar system (with a radius of 2575km) (the largest satellite in the solar system is Jupiter's Ganymede with a radius of 263 1km).
7. Uranus is the seventh planet in the solar system from the inside out (18.37~20.08 astronomical units). Its volume ranks third in the solar system (larger than Neptune) and its mass ranks fourth (smaller than Neptune), and it rotates almost horizontally around the sun.
Uranus' atmosphere is mainly composed of hydrogen, helium and methane. It is speculated that the interior may contain rich heavy elements. The mantle is composed of methane and ammonia ice, which may contain water. The inner core consists of ice and rocks. Uranus is the coldest planet in the solar system, with a minimum temperature of only 49K(-224℃).
8. Neptune is a distant planet among the eight planets. According to the distance between the planet and the sun, Neptune is the eighth planet, the fourth largest planet in diameter and the third largest planet in mass. Its brightness is only 7.85, which can only be seen by astronomical telescopes. Because of its light blue light, westerners call it Neptune, the sea god in Roman mythology. Translated into Neptune in Chinese.
Neptune is smaller in diameter and volume than Uranus, but its mass is larger than Uranus, which is about 17 times that of the earth, while its sister planet Uranus is about 14 times that of the earth because of its low density.
Neptune's atmosphere is dominated by hydrogen and helium, with a trace of methane. Methane in the atmosphere is one of the reasons why the earth appears blue. Neptune has the strongest storm in the solar system, and the measured wind speed is as high as 2100 km/h/h.
The temperature of Neptune's cloud top is -2 18 ℃(55K), because it is farthest from the sun and is one of the coldest regions in the solar system. Nevertheless, Neptune has a fiery interior, and the temperature of Neptune's core is about 7000℃, which is similar to most known planets.
Extended data:
The eight planets in the solar system all run in nearly circular orbits on almost the same plane and revolve around the sun in the same direction. Except Venus, the rotation direction and revolution direction of other planets are the same. Comets revolve around the sun in the same direction, mostly in elliptical orbits, and generally have a long period of revolution.
The celestial bodies orbiting the sun are divided into three categories: planets, dwarf planets and small celestial bodies in the solar system.
Planets are celestial bodies with sufficient mass around the sun.
Such celestial bodies:
1. Enough mass to make it a sphere;
2. Small celestial bodies that can empty adjacent orbits.
3. A satellite that is not a planet or a celestial body that is not a star.
There are eight celestial bodies that can be called planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
On August 24th, 2006, the 26th International Astronomical Union was held in Prague, Czech Republic, which redefined the word planet, excluded Pluto from the big planet for the first time, and formed a new classification of Pluto, Ceres and Eris: dwarf planet. A dwarf planet does not need to remove small objects near its orbit. Other celestial bodies that may become dwarf planets include Cedena, Ercus and Chuangshen.
From the first discovery of 1930 to 2006, Pluto was regarded as the ninth largest planet in the solar system. However, at the end of the 20th century and the beginning of the 20th century, many celestial bodies similar in size to Pluto were discovered in the solar system, especially Mars, which was clearly pointed out to be bigger than Pluto (according to the data sent back by 20 15 travelers, Mars was still bigger than Pluto), which seriously threatened Pluto's status.
Other celestial bodies orbiting the sun belong to the solar system.
Satellites (the moon and other celestial bodies) are not small celestial bodies in the solar system because they revolve around planets, dwarf planets or small celestial bodies in the solar system instead of the sun.
Astronomers use astronomical units (AU) to measure distances in the solar system. 1AU is the average distance from the earth to the sun, which is about1.500 million kilometers (93 million miles). The distance between Pluto and the sun is about 39AU, while Jupiter is about 5.2AU.
The most commonly used length unit for measuring the distance between stars is light years, and 1 light year is equivalent to about 63240 astronomical units. The distance between the planet and the sun changes periodically with period of revolution. The closest position to the sun is called perihelion, and the farthest position is called apohelion.
Sometimes the solar system is informally divided into several different regions: "inner solar system", including four terrestrial planets and the main asteroid belt; The rest is the "outer solar system", including all celestial bodies outside the asteroid belt. Other definitions include areas outside Neptune, and the four big planets are called "intermediate zones".
reference data
Baidu encyclopedia-solar system