Dwarf planets are planets only, but much smaller, but not too small either to be considered Minor planet.
Let's dive deep into it.
Dwarf planets are planetary-mass object (just like major planets) that are in direct orbit of Sun and are massive enough to maintain a hydrostatically equilibrious shape (precisely a spheroid shape), but has no 'clearance in the neighbourhood'.
Clearance in the neighbourhood means that the celestial body is gravitationally dominant in the area and there are no bodies of comparable size other than its natural satellites.
What is Dwarf Planet? - According to IAU
IAU (International Astronomical Union), an international body sets definitions for planetary science.
IAU defines Dwarf planet as:
- Body with direct orbit of Sun
- Body has sufficient mass to assume a nearly around shape (spheroid shape)
- Body has no clearance in the orbit / Body is not gravitationally dominant
- Body is not a natural satellite
Dwarf planets of the Solar System
There are five officially recognized dwarf planets by the IAU.
Pluto is the largest dwarf planet in the system. It was long considered as a planet before reclassifying it as dwarf planets.
Etymology of Pluto: Pluto is named after the ancient Roman god of Underworld.
Pluto has 5 known moon: Charon, Hydra, Nix, Kerberos (P4) and Styx (P5).
Ceres is the closest dwarf planet to the Sun as well as to the Earth located in main asteroid belt. Some scientists even call Ceres as 'Embryonic Planet'. It could have became a full-fledged planet, when billions of years ago, Jupiter stepped in its development phase and gravitational perturbations halted this process and and thus stopped it from becoming a planet.
Ceres is also the smallest and the least massive dwarf planet in the solar system.
Ceres is the only dwarf planet with no moons.
Ceres is the only dwarf planet in the inner solar system, rest lies in trans-neptunian region.
Ceres ended up becoming a left-over debris of planet planetary formation.
Etymology of Ceres: Ceres is named after the ancient Roman goddess of corn and harvest.
Eris is the farthest dwarf planet in the solar system. Eris has the greatest mass of all the dwarf planets followed by Pluto.
Etymology of Eris: Eris is named after the ancient Roman goddess of discord and strife.
It is an oddly shaped (an ellipsoid) dwarf planet. Its odd shape is result of fast rotation in the solar system.
Haumea is the least spherical of the dwarf planets.
Etymology of Haumea: Haumea is named after the god of fertility in Rapa Nui mythology (Pascuense mythology).
Moon: Hi’iaka and Namaka
Etymology of Makemake: Makemake is named after the Hawaiian goddess of fertility and childbirth.
Moon: MK 2
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Curated by: Aakash Gautam