After Pluto stopped being classified as a planet, there was no lack of interest in announcing the existence of other planets in the Solar System
Astronomical discoveries are some of the science news that invariably make the headlines.
From time to time there are news related to the discovery of new planets in our solar system, but it turns out that many times they are not so new, nor are they planets.
Size does not matter
If they studied their basic education before 2006, it is very likely that when answering how many planets there are in the Solar System they will say that there are nine. Or maybe they hesitate a bit, is it eight?
Because maybe, sometime in the last 14 years, you’ve read something about Pluto stopped being classified as a planet. They were even angry or saddened by the apparent demotion of the category that the planet farthest from the Sun suffered. Well, planetoid or dwarf planet.
The name of dwarf planet seems to indicate a size smaller than normal, although in reality that is not the current reference used by the International Astronomical Union.
Planets and planetoids share two characteristics: they are objects with orbit around the sun and that they have enough mass for their gravity to give them a spherical shape.
Who commands here?
What distinguishes the planets is that they have what is called orbital dominanceIn other words, they have cleared their orbit of other objects – other than their natural satellites.
Pluto does not have orbital dominance: that is, there are many other objects of considerable size there. That is why it is a planetoid. One that looks a lot like a planet because it also has a satellite: Charon. And it is not one of a kind.
Passing the orbit of Pluto are many other smaller objects that have been classified as planetoids: Haumea, Makemake and Eris, among others.
The latter is the second largest planetoid, even at some point it was thought to be larger than Pluto and in the press headlines it was mentioned as a « Tenth » planetBut it is neither bigger than Pluto, nor is either a planet.
The farthest region of the Solar System is not the only suitable neighborhood for planetoids. At asteroid beltBetween Mars and Jupiter, there are a couple of objects that can be classified as planetoids.
One of them, Ceres, was discovered in 1801, even then it was thought to be a planet: later when more and more objects were discovered there, it was classified like all other asteroids. But due to its round gravity, we now consider it as a planetoid.
Until a couple of years ago Ceres was the only internal planetoid, in 2019 it was described that another object in the asteroid belt could be classified as follows: Hygiea, which was discovered in the 19th century, but recently we have been able to see more clearly that it has a very spherical shape.
Although it is certainly interesting to think that we have more or less close neighbors to a pair of planetoids, neither of them can hope that they will soon be upgraded: it is very difficult to achieve orbital dominance when you live in the asteroid belt.
And lest you be sad about Pluto, don’t forget that regardless of the rankings, he is still there in his orbit, after Neptune, circling the Sun, and has no plans to go anywhere else.