In 2006, the International Astronomical Union kicked Pluto out of the nine planets and downgraded it to a dwarf planet, even at that time the astronomical community controversy was not small, NASA's chief researcher on Pluto, Alan Stern, openly ridiculed this resolution as annoying and did not represent the views of scientists in the entire astronomical community.
Coincidentally, New Mexico announced that Pluto would be considered a planet forever, and set a special planet day for Pluto, March 13, 2007. The Illinois Senate in 2009 followed suit, and the reasons they gave could not have been more straightforward, because Clyde Tombaugh, who discovered Pluto, was born in Illinois.
It has been many years, but during this time, scientists have called for the need to restore Pluto's planetary identity. At the same time, they also questioned the rules for the definition of planets, arguing that the substantial bodies orbiting the sun can be classified as planets, which means that the number of planets in the solar system will reach about 150!
Regarding the fact that Pluto was kicked out of the nine planets, the problem is actually on the surrounding "Pluto-like celestial bodies", which makes many people wonder how terrible the real Pluto is. And what are the strangely named "Pluto-like objects" around it?
At present, the largest dwarf planet in the known solar system is Pluto, but its mass ranks behind the dwarf planet "Erus", and if the range is expanded to all the stars orbiting the Sun, then Pluto's volume can be shot to the ninth. Some people think that Pluto is terrible, probably because of its name, or it may be because of its unusual orbit.
The mass and volume of Pluto is not as large as that of the Moon, but the inclination and eccentricity of its orbit are very high, with a rotation period of 6 days, 9 hours, 17 minutes and 36 seconds, and an orbital period of 247.94 years. Pluto's orbit can be described by the word "chaos", it is difficult to determine the exact location of millions of years later, and its orbital period and semi-major axis are still moving towards a longer trend. Sometimes it also enters the inner side of Neptune's orbit, which inevitably makes people worry about whether the two will suddenly collide together one day, but fortunately, later scientific studies have shown that such things generally do not happen because of orbital resonance.
Since Pluto's orbit is so unusual, it naturally means that the four seasons on the planet change differently, whether it is the winter solstice or the summer solstice, Pluto has a quarter of the polar day, and a quarter of the polar night.
NASA in the United States in 2006 officially opened the "New Horizons" mission, and Pluto is one of the main objects of observation, 2015 to 2016 have sent back a lot of amazing images, on Pluto, its mountain composition is water ice, weak atmosphere only found methane, nitrogen and carbon monoxide, so far can not determine whether the New Horizons probe photographed whether the clouds. Including Pluto and its five moons, this made researchers realize that the real Pluto looked more like a planet than ever thought!
On the icy Pluto, not only the existence of subsurface oceans and relatively stable atmosphere, but also may be because of the active tectonic activity of volcanic activity, Pluto and the eight planets of the solar system, the same rotation around the sun, the appearance is also spherical, the only non-compliant asteroid requirements are one point, that is, the area near the orbit is not cleared, its own mass is far smaller than the total mass of other objects in the orbit, accounting for about 7%, which makes some scientists feel that the decision to classify Pluto to a dwarf planet at that time. Isn't that sloppy?
The "Pluto-like object" mentioned earlier, in fact, since June 2008, there has been a Pluto-like object, which is specifically used to refer to those natural enemies that are similar to Pluto, not only similar in orbit, but also resonate with the orbit of Neptune.
It is easier to understand that when Neptune orbits the sun for 3 weeks, the object just completes the orbit around the sun for 2 weeks, maintaining a 3:2 resonance law. It should be known that nearly a quarter of the Kuiper Belt where Pluto is located is a Pluto-like object, a term that was specifically set up after Pluto was relegated to a dwarf planet, specifically to refer to those small bodies similar to Pluto that are also trapped by resonance orbits.
All in all, Pluto was indeed once defined as one of the nine planets of the solar system, but when many similar stars were later discovered, there were only eight planets left in the solar system, and then the definition of planets was specially formulated. Some people may wonder, whether a planet is a planet or how much can a dwarf planet have to do with us.
In fact, in addition to not emptying other celestial bodies in their orbits, dwarf planets, although they also look like the shape of a round ball, their volume is generally between the planet and the asteroid.
Whether it is a dwarf planet, asteroid, or a planet, there is a clear basis for its division, Pluto from a planet to a dwarf planet is not unjust, which is very meaningful for scientists to find life planets other than Earth, after all, we know that what can make life flourish is an Earth-like planet like Earth, so when looking for exoplanets, more eyes are also locked on the same Earth-like planets, at least in terms of probability, the possibility of life will be greater.