Pluto was discovered by the American astronomer Clyde Tombaugh in 1930 and then qualified as a fully-fledged Solar System planet and maintained this status until 2006. It was in this year that the International Astronomical Union (IAU) introduced the concept of a dwarf planet and classified the planet in this category. Therefore, the answer to the question "is Pluto a planet?" is no, not anymore (but who knows what the future holds?).
Pluto Interesting Facts
|Official Name||(134340) Pluto|
|Object Type||Dwarf planet|
|Distance from Sun||39.5 AU|
|Diameter||1,477 miles / 2,377 km|
|Mass||1.303 × 1022 kg (0.0022 M⊕ / 0.22% Earths)|
|Length of Year (Orbit)||247.94 Earth years / 90,560 Earth days|
|Known Moons||5 (Charon, Nix, Hydra, Kerberos, Styx)|
How Is a Dwarf Planet Different From an "Ordinary" Planet?
A dwarf planet is a celestial body that has not cleared its orbit and has not become gravitationally dominant in its area, which is why it shares its orbital space with other celestial bodies of a similar size (however scientists, astronomers, and astrophysicists are still debating this definition).
Moons of Pluto
The planet has 5 natural satellites:
- Charon (I) - Pluto's largest moon. It was first observed by James Christy in 1978. It is so large in relation to Pluto (there is no the slightest comparison to the Earth-Moon system) that the Pluto-Charon system can be considered a double dwarf planet.
- Nix (II) - discovered in 2005.
- Hydra (III) - similarly to Nix, discovered in 2005. Both of these moons (Nix and Hydra) were first sighted by the Hubble Telescope. They don't have a "regular" round shape - they look more like elongated, irregular pieces of rock.
- Kerberos (IV) - discovered in 2011, also by the Hubble Telescope.
- Styx (V) - 2012, again thanks to the Hubble Telescope.
Other Dwarf Planets in the Solar System
At the time of writing this, the International Astronomical Union (IAU) officially recognizes 5 celestial bodies as dwarf planets in the Solar System:
Of this group, only Ceres orbits in the asteroid belt between the orbits of Mars and Jupiter. The remaining objects orbit beyond Neptune's orbit and are therefore also referred to as plutoids.
No, it is no longer a fully-fledged Solar System planet anymore. However, it was until 2006, when the IAU (International Astronomical Union) introduced the concept of a dwarf planet and classified the planet in this category, similarly to planets Ceres, Haumea, Makemake, and Eris.
Hi, I'm Paweł! I'm an astrophotographer, full-time astrophotography blogger, passionate stargazer, and amateur astronomer. Here on Astro Photons, I share my astrophotography, space, and astronomy knowledge to help beginners to make their first steps into the hobbies.