Is Pluto the Nine Planets and why is Pluto not one of the Eight Planets?

It used to be. Even our high school geography teacher summed up the distance between the nine planets and the sun in this way: water, gold, earth, fire, wood, earth, heaven, sea, and underworld.

Pluto is no longer considered a planet, but is included as a "dwarf planet".

At 9:20 p.m. Beijing time on the 24th, the General Assembly of the International Astronomical Union voted on Resolution 5, partially adopting a new definition of planets, and Pluto was excluded from the list of planets and included it as a "dwarf planet".

The International Astronomical Union (IAU) relinquished the idea that the eight planets of the solar system other than Pluto were "classical planets", thus confirming that there were only eight planets in the solar system and that Pluto had been downgraded to a "dwarf planet". The first plan that was previously rumored proposed that the solar system would be aborted with plans to add three more second-order planets.

In 1930, the American astronomer Tombo discovered Pluto, and at that time misestimated the mass of Pluto, thinking that Pluto was larger than the earth, so he named it a large planet. However, after nearly 30 years of further observation, it was found that its diameter was only 2,300 kilometers, which was smaller than that of the Moon.

The original proposal of the Planetary Definition Committee was to downgrade Pluto to a second-class planet in addition to identifying Venus, Saturn, Jupiter, Mercury, Earth, Mars, Uranus, and Neptune as classical planets, and to add Ceres, Charon, and 2003UB313 to second-class planets.

This one is inside, good luck.

The reason why Pluto is not one of the eight planets (on the afternoon of August 24, 2006, at the 26th International Astronomical Union, a resolution was passed by astronomers to officially classify Pluto as a dwarf planet and remove it from the list of self-stars).

1. Pluto is very small: Many people think that Pluto is very small, like an ordinary asteroid, but in fact this dwarf planet is 2,360 kilometers in diameter, which is two-thirds the diameter of the Moon and three-quarters of Europa. Pluto's largest moon, Charon, is about 1,207 kilometers in diameter.

2. Pluto was once a "moon" of Neptune: In 1965, researchers discovered an orbital resonance - there is an optimal gravitational point in the orbit between Pluto and Neptune, and this orbital resonance can prevent the two planets from getting too close to each other.

3. Pluto is an icy planet: Pluto's surface is covered with a large amount of ice, including frozen nitrogen and methane, but Pluto as a whole is twice as dense as ice water, and the mass of this dwarf planet is made up of two-thirds of rock and one-third of icy water, so Pluto is precisely a rocky planet with an ice crust.

4. Pluto is always in "darkness": Pluto orbits about 4.8 billion kilometers from the Sun, so many people speculate that the planet's surface has been in darkness.

Alan Stern, project leader of the New Horizons probe at the Southwest Research Institute in Colorado, said: "This is not the case, even the midday sunlight that hits Pluto is lower than one would expect, and it could be like very gloomy weather on Earth or twilight." ”

5. Pluto lacks air: In the 80s of the last century, researchers discovered that Pluto has an atmosphere, which mainly contains nitrogen, just like the Earth's atmosphere. But Pluto's air also contains carbon monoxide and methane, which is thinner than Earth's atmosphere and extends more into the space environment.

6. Pluto's orbit is too flat: Pluto's orbit is elliptical, with the closest distance to the Sun being 100 million kilometers and the farthest distance being 100 million kilometers. The dwarf planet's orbit is inclination of 17 degrees relative to the ecliptic, the plane of the Earth's orbit around the Sun, and Pluto's orbital parameters are completely different from those of the other eight solar system planets.

No.

The eight planets are the eight large planets of the solar system, according to the distance from the sun from near to far, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, in the 26th session of the International Astronomical Union held in Prague on August 24, 2006 in Resolution 5, Pluto (Pluto) is classified as a dwarf planet, in addition to the name of the eight planets.

Pluto (asteroid number: 134340pluto; Astronomical code: , unicode code:

U+2647) is a dwarf planet in the Kuiper Belt. Pluto was the first Kuiper Belt object to be discovered. Pluto is the largest known dwarf planet in the solar system and the second most massive.

Categories: Education, Science, >> Science & Technology.

Problem description: Data comparison. Analysis:

Since Pluto is significantly different from the other eight planets, it is not considered the ninth planet in the solar system, but should be classified as an asteroid. The reasons for this are:

First, the track is special. The eight planets orbit the Sun in an elliptical orbit that is close to circularity, while Pluto's orbit is extremely long and flattened, with a heart rate of 0 248. Its aphelion is 7.4 billion kilometres, while its perihelion is only 4.5 billion kilometres, and it is within Neptune's orbit.

Pluto is the only one whose orbit is inserted into the adjacent planets;

The second is the abnormal rotation. Except for Mercury and Venus, which rotate slowly due to the gravitational pull of the sun, the rotation period of the eight planets is within 9 to 25 hours, while the rotation period of Pluto, which is far away from the sun, is 6 days, 9 hours and 17 minutes, which is contrary to the physical nature of the planetary sequence.

The third is small. According to the material available so far, Pluto may be smaller than the Moon;

Fourth, it has geostationary satellites. On July 7, 1978, American astronomer Christie discovered that Pluto's moon "Charon" is about one-third the diameter of Pluto, and its orbital period is equal to Pluto's rotation period. Among the many natural satellites of the planets of the solar system, this is the only synchronous satellite.

For Pluto, the "Charon" moon appears so large that it is thought that it may not be a moon of Pluto, but a binary star system with Pluto;

Fifth, its composition is the same as that of the Kuiper object. Since the 90s of the 20th century, astronomers have discovered a number of asteroids near Neptune and Pluto, which are similar in composition to Pluto, mainly rocks and ice, known as the Kuiper Object or the Kuiper Asteroid Belt. As a result, some astronomers believe that Pluto could also be one of these asteroids.

Pluto is a dwarf planet.

Pluto was discovered by Clyde Tombaugh in 1930 and considered it the ninth planet. The discovery of a number of ice-made objects in the Kuiper Belt after 1992 with a mass similar to that of Pluto challenged Pluto's status as a planet. In 2005, the discovery of Eris was even 27% more massive than Pluto, and the International Astronomical Union (IAU) officially defined the concept of planets the following year.

The new definition excludes Pluto from the planetary range, classifying it as a dwarf planet (Pluto-like object).

According to the definition of a planet voted by the Assembly of the International Astronomical Union in Prague, the Czech capital, on 24 August 2006, the difference between a planet and a dwarf planet is whether it has cleared other celestial bodies in its orbit. In other words, if a celestial body is defined as a planet, it should be the largest of the local celestial groups. A local group of objects refers to a collection of objects that pass through and approach the orbit of a celestial body, and in layman's terms, other celestial bodies around the orbit of this celestial body.

Planets are larger than the other celestial bodies around their orbits combined.

According to the new definition, a celestial body that also has sufficient mass and is spherical in shape, but cannot clear other objects in the vicinity of its orbit is called a "dwarf planet". Pluto is a dwarf planet. Other objects orbiting the Sun that do not meet the above conditions are collectively referred to as "small bodies of the solar system".

Not the ninth largest planet, because Pluto is classified as a dwarf planet, which is between a planet and an asteroid in size, so it cannot be called a large planet. Check the encyclopedia for details.

Or a planet anyway!