How many planets are there in space?

As of 20 13, there are eight planets in the solar system, namely: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

1, mercury

Mercury (English: Mercury, Latin: 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 and is smaller than Pluto. 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

Venus, one of the eight planets in the solar system, is the second planet in the distance sequence 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, which is called Chang Geng.

2065438+September 2, 2008, Tianyu staged a beautiful celestial phenomenon of "combination" of planet Venus and star corner. These two bright stars will be in close contact, and a romantic "star attraction" will be staged for the public.

3. Earth

The earth is one of the eight planets in the solar system, ranking third in the order from near to far from the sun. It is also the earth-like planet with the largest diameter, mass and density in the solar system, with a distance of1.500 million 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.

4. Mars

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% and a mass of 14% of the earth.

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).

Mars is called "the twinkling star" in China's ancient books and "the mythical star of Mars" in ancient western countries (ancient Rome). It is the only guardian star of Aries in the twelve constellations, not the guardian planet of Scorpio.

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.

5. Jupiter

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.

Because Jupiter, Saturn, Uranus and Neptune are all gaseous planets, they are also collectively called woody planets (Jupiter and Saturn are collectively called gaseous giants).

Jupiter is a giant gas planet, accounting for 70% of the mass of all planets in the solar system. It is mainly composed of hydrogen, accounting for 75% of its total mass, followed by helium, accounting for 25% of its total mass. The rock 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.

6.saturn

Saturn (English Saturn, Latin Saturn) is one of the eight planets in the solar system, with the sixth distance (from near to far) from the sun. The mass and diameter are second only to Jupiter, and they belong to the gas giant planet with Jupiter.

In ancient Europe (ancient Greece), Saturn was called Cronus (ancient Greek: κ ρ? νο? ; English: Chronos), also called revitalization or revival in ancient China.

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. Saturn's rings can be seen in the outermost atmosphere, although they sometimes exist for a long time.

Saturn's wind speed is as high as 1800 km/h, which is obviously faster than Jupiter. Saturn's planetary magnetic field strength is between the earth and Jupiter, and the airflow is very fast.

7. Uranus

Uranus, one of the eight planets in the solar system, 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 it may be rich in 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

Neptune is a distant planet among the eight planets in the solar system. 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.

Neptune's 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.

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