Dwarf planets did not actually exist until 2006. Then they were allocated to a new class of space objects. The purpose of this transformation was to introduce an intermediate link between large planets and numerous asteroids to prevent confusion in the names and statuses of new bodies found beyond the orbit of Neptune.
Definition
Then, back in 2006, the next meeting of the IAU (International Astronomical Union) took place. On the agenda was the issue of specifying the status of Pluto. In the process of discussion, it was decided to deprive him of the "rank" of the ninth planet. MAS has developed definitions of some space objects:
- A planet is a body that revolves around the Sun, massive enough to maintain hydrostatic equilibrium (that is, have a rounded shape) and clear its orbit from other objects.
- An asteroid is a body that revolves around the Sun, has a small mass that does not allow it to achieve hydrostatic equilibrium.
- A dwarf planet is a body that revolves around the Sun, maintaining hydrostatic balance, but not massive enough to clear its orbit.
Pluto was among the latter.
New status
Pluto is also classified as a trans-Neptune object. Like some other dwarf planets, it belongs to the bodies of the Kuiper belt. The impetus for the revision of the status of Pluto was the numerous discoveries of objects in this remote part of the solar system. Among them was Eris, superior to Pluto in mass by 27%. Logically, all these bodies had to be classified as planets. That is why it was decided to revise and concretize the definitions of such space objects. So there were dwarf planets.
Tenth
Not only Pluto was "demoted." Eris, before the meeting of the IAU in 2006, claimed to be the "title" of the tenth planet. It surpasses Pluto in mass, but inferior to it in size. Eris was discovered in 2005 by a group of American astronomers searching for trans-Neptune objects. Originally it was called Xena or Xena, but later they began to use the modern name.
Eris, like other dwarf planets of the solar system, has hydrostatic equilibrium, but is not able to clear its orbit from other cosmic bodies.
Third on the list
The next largest after Pluto and Eris is Makemake. This is a classic Kuiper belt object. An interesting story has the name of this body. As always, after opening it was assigned the number 2005 FY 9 . For a long time, the team of American astronomers who discovered Makemake called him “Easter Bunny” (the discovery was made a few days after the holiday).
In 2006, when the new column “Dwarf planets of the solar system” appeared in the classification, it was decided to name 2005 FY 9 differently. According to tradition, the classical objects of the Kuiper belt are named after the deities associated with the creation. Make-make is the creator of humanity in the mythology of the Rapanuy, the original inhabitants of Easter Island.
Haumea
Dwarf planets in the solar system include another trans-Neptune object. This is Haumea. Its main feature is a very fast rotation. According to this parameter, Haumea is ahead of all known objects with a diameter of more than one hundred meters in our system. Among dwarf planets, the object takes fourth place in size.
Ceres
Another cosmic body belonging to this class is located in the Main asteroid belt lying between the orbits of Jupiter and Mars. This is Ceres. It was opened in early 1801. For some time it was considered a full planet. And in 1802, Ceres was attributed to asteroids. The status of the cosmic body was revised in 2006.
Dwarf planets from their large neighbors are mostly distinguished by their inability to clear their own orbit of other bodies and space debris. It’s hard to say how convenient this innovation is for use - time will tell. In the meantime, only a little subsided debate over the downgrade of Pluto. However, the value of the former ninth planet and its bodies for science remains high regardless of how they are called.