#冥王星到底该不该被降为矮行星? #
In 2006, Pluto was removed from the list of planets in the solar system and demoted to a dwarf planet. Of course, long before 2006, the astronomical community was controversial about Pluto's status, and finally in 2006, Pluto lost its status as a planet and became a dwarf planet.
However, to this day, there are still many people who are haunted by Pluto's downgrading. So, should Pluto be downgraded to a dwarf planet?
1. Subjective and objective
In fact, from a certain point of view, astronomy has both subjective and objective components.
The so-called objectivity is because no matter how human beings establish Pluto's identity, it does not affect Pluto's existence since ancient times. And when it comes to the time when there was no living thing on the earth since ancient times, Pluto has existed and revolved around the sun. And this also shows the objectivity of astronomy - even if there is no such thing as human beings on the earth, it does not affect the objective existence of the solar system and various celestial bodies in the solar system.
The so-called subjective is because human beings need to classify celestial bodies according to their characteristics, and formulate concepts based on summaries, determine the criteria for planets, and determine the criteria for stars. And this criterion is summarized and then summarized and prescribed by human beings based on objective facts. This is subjectivity. Of course, there is not much room for maneuver in this subjectivity. After all, no matter how subjectively human beings formulate concepts, they cannot define the Sun as a planet and Mars as a satellite. There must always be certain objective criteria.
So with that in mind, we can consider the concept of Pluto.
2. Is Pluto a planet or not?
In fact, the concept of astronomy is constantly revised, and the concept is constantly revised according to different times and different degrees of development of astronomy.
Mankind's initial observation of astronomy was relatively primitive and intuitive. Therefore, the concept of astronomy is simply divided into three types: the sun, the moon, and the stars. Of course, there are also some "stars" among these stars: such as Sirius, Mars, and Jupiter, all of which are typical "stars". The ancients also classified Mars and Sirius into the same category, that is, they are both stars.
However, in modern times, with the development of human astronomical research technology, human beings have discovered that the previous division is undoubtedly full of extensive patterns: that is, according to the attributes, Sirius belongs to the star, and Mars belongs to the planet, and the two cannot be classified into the same category; according to the galaxy to which it belongs, Mars is a celestial body inside the solar system, and Sirius is a star outside the solar system. Therefore, astronomy has further divided the classification of celestial bodies: the concepts of stars, planets and moons, and even the concept of asteroids, have a relatively clear concept.
When Pluto was discovered in 1930, it was believed that all the conditions of Pluto met the standards of a planet at that time, so Pluto should be a planet - although later humans also realized that Pluto's actual size was not large enough to affect the orbits of Uranus and Neptune, but it did not affect mankind to continue to regard Pluto as a planet.
However, with the advancement of human astronomical observation technology, humans have discovered a large number of celestial objects similar to Pluto in the vicinity of Pluto. At the same time, many details of these celestial bodies are different from those of planets (such as orbital problems), so humans decided to revise the concept of planets, and with the revision of the concept, Pluto was also downgraded to a dwarf planet - those objects that are similar to Pluto are also classified as dwarf planets.
Therefore, whether Pluto is considered a planet or not depends on the astronomical theory of which era.