Pluto was once one of the nine planets, what caused it to be kicked out of the ranks of the nine?

Pluto is currently a dwarf planet. A long time ago, everyone may know the nine planets of the solar system, these nine planets are: Mercury, Venus, Earth, Mars, Saturn, Jupiter, Uranus, Neptune and Pluto, and later scientists found that Pluto does not seem to fit the characteristics of the planets, so Pluto was removed and downgraded, so the nine planets became the eight planets.

Pluto is about 70 kilometers from the Sun, and it takes 5 hours for the sun's light to reach Pluto, which is a very long time. At the same time, it also means that Pluto is very cold, its day and night temperature are basically the same, it is located outside the cold zone of the solar system, and Pluto because its orbit and the ecliptic are very consistent, and its mass and distance are consistent, and finally the International Astronomical Union decided to name Pluto the ninth planet.

Later, with the continuous development and progress of science and technology, scientists have discovered several celestial bodies similar to Pluto, and their size is generally larger than Pluto, this celestial body is Eris, and observing other planets at the same time, you will find that they all have their own moons, and although Pluto has satellites, their mass is too small to have this characteristic of planets.

In the end, the International Astronomical Union voted unanimously at the 2005 World Astronomical Congress to remove Pluto and downgrade it to a dwarf planet, and astronomers later decided that Planet Nine must be defined again. But when astronomers discovered Sedna, the decision was canceled, and the solar system became eight planets.

But there are still many scientists who believe that there is a ninth planet in the solar system, and that it may be very large, but because it does not emit light, it is like looking for a needle in a haystack to find it in the vast solar system. The reason why Planet 9 is believed to exist is that the solar system is so large that it has a diameter of 2 light-years, and it takes 2 years to fly out of the solar system at the speed of light.

It is clear that scientists have not given up the search for Planet 9, and there have been many international competitions to discover Planet 9, but at present, none of the candidates meet the characteristics of Planet 9, and scientists have begun to simulate the environment and orbit of the planet Earth in the laboratory. As for discovering it, it is still a fantasy for now.

Mainly because Pluto is particularly small. Moreover, this trajectory parameter of Pluto is completely different from that of the Sun, so it is excluded. It also does not meet the requirements of this planet.

This is because after studying the planets, people found that Pluto is too small. Not enough to be the nine planets.

Because Pluto is very far away from the Earth and relatively small, with the development of science, scientists have discovered that Pluto does not belong to the planetary series.

In fact, the answer has only been available since 2006, which means that before that, there were more than eight planets in the solar system. At this point, many readers might be confused, right? Impossible.

How can we still be confused about the number of planets in the 21st century? It was even confirmed that there were eight planets in the solar system in 2006? Well, that's not true, either, because before 1930, it was known that there were eight planets in the solar system.

Until today's protagonist, Pluto, one of the original nine planets, was introduced, confirmed by humanity in 1930. So Pluto was a member of the solar system for 76 years, from 1930 to 2006. So why are scientists kicking a 76-year-old planetary out of the top nine?

<>Maybe you think it's a good idea, since Pluto is no longer considered one of the nine planets, it doesn't fit the definition of a planet, so some eager readers looked it up online for that definition. You see, the definition of planets says. Rules.

The object must orbit the sun. This object must have enough mass for its gravitational pull to exceed its solid stress and reach hydrostatic equilibrium, which means it has a spherical shape. This object has enough gravitational pull to clear the area around its orbit (no objects with more mass than it are allowed).

For Pluto, the first two are true, but the third is a problem. It was found that Pluto's orbit is markedly different from that of the other eight planets, with a large inclination between the orbit and the ecliptic (17 degrees), and because its perihelion is shorter from the Sun than Neptune's perihelion, it is periodically located within Neptune's orbit; In addition to this, the Kuiper area, where Pluto is located, has a number of smaller objects, including one called Eris, which is even more massive than Pluto. It is clear that Pluto cannot be called a planet.

Note, however, that while Pluto clearly does not fit the definition of a planet, when did that definition come about? Yes, in 2006, to put it bluntly, a new definition of planets (or a clear classification of objects in the solar system) was proposed, removing Pluto from the list of planets.