Photo of the dwarf planet Ceres, taken by the Dawn space probe.
A dwarf planet is a planet that follows 2/3 of the planet criteria. All of them are smaller than our Moon. The IAU made the group in 2006. There are six minor planets that are considered “dwarf planets” in our Solar System, but scientists think there may be hundreds or even thousands more. Their names are Ceres, Pluto, Haumea, Makemake, Quaoar, Eris (for the one accepted by the IAU).
Definition[]
To be a dwarf planet, an object has to…
- It orbits around the Sun.
- It maintains hydrostatic equilibrium.
- It is not a moon of any other planet.
To be a major planet, an object has to…
- It orbits around the Sun.
- It maintains hydrostatic equilibrium.
- (X) It clears its neighborhood (which dwarf planets do not follow)
Size and Mass[]
Dwarf planets are extremely small and not massive compared to planets. Pluto, in fact, is smaller and less massive than Earth's moon, being able to fit in the United States. Eris is less then half of the size of Mercury.
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Charon, the largest moon of Pluto, sometimes referred to Pluto as a binary partner.
Moons[]
Because of their size and mass, they have smaller gravitational pulls, however, they can still maintain hydrostatic equilibrium. Pluto's moon, Charon, is Pluto's largest moon. Pluto, however is home to five other moons, yet they are so far away from Pluto because of Pluto's weak gravitational pull. Currently, there are two moons known around Haumea, one around Quaoar, one around Makemake, and one around Eris.
List[]
| Name | Date Accepted | Diameter (kilometers) | Mass (Earth Masses) | Semi-Major Axis | Number of Moons | Discovery Year |
|---|---|---|---|---|---|---|
| Ceres | August 24, 2006 | 939.4 | 0.000157 | 2.77 AU | 0 | 1801 |
| Pluto | August 24, 2006 | 2,376.6 | 0.0022 | 39.482 AU | 5 | 1930 |
| Haumea | June 2008 | 1,632 | 0.00066 | 43.116 AU | 2 | 2004 |
| Quaoar[1] | December 8, 2023 | 1,159 | 0.0002 | 43.694 AU | 1 | 2002 |
| Makemake | June 2008 | 1,429 | 0.00053 | 45.43 AU | 1 | 2005 |
| Eris | August 24, 2006 | 2,326 | 0.0028 | 67.864 AU | 1 | 2005 |
An artist’s impression of Sedna, one of the most well known dwarf planet candidates.
Dwarf Planet Candidates[]
Dwarf planet candidates are objects similar to dwarf planets and that meet all the criteria, but are not officially considered to be them by the IAU. The largest 4 are Gonggong, Sedna, Orcus, and Salacia. Some other notable ones are Máni, Ixion, Varuna, Varda, 2013 FY27, and Hygiea.
Criteria[]
Mass[]
To be classified as a Dwarf Planet, the object must have enough mass in order for it to maintain hydrostatic equilibrium, the process where an object’s gravity is able to form itself into a nearly spherical shape.
Orbit[]
Dwarf Planets must be in orbit around the sun, not another planet. Also, Dwarf Planets must “not clear their orbit of neighboring objects” or to not be the dominant object in their region compared to objects that orbit close to or intersect it. Any object that does dominate the area it orbits around would be classified as a planet rather than a dwarf planet.
Radius or Diameter[]
The minimum diameter that an object would usually maintain hydrostatic equilibrium is around 400 km. However, factors such as density can cause some doubt for objects that have not been visited by spacecraft.
List of Dwarf Planet Candidates[]
| Name | Diameter (Kilometers) | Accepted by Brown et al. | Accepted by the IAU |
|---|---|---|---|
| 225088 Gonggong | 1230-1535 | Yes | Possibly[2] |
| 50000 Quaoar | 1086 | Yes | Yes |
| 90377 Sedna | 995 | Yes | |
| 90452 Orcus | 910 | Yes | |
| 120347 Salacia | 846 | Yes | |
| 307261 Máni | 797 | Yes | |
| 174567 Varda | 749 | "Highly likely" | |
| 28978 Ixion | 710 | "Highly likely" | |
| 20000 Varuna | 668 | "Highly likely" | |
| 19521 Chaos | 600 | "Highly likely" | |
| 10 Hygiea | 434 | "Probably" |
Ceres, compared to the asteroid Vesta, and the Earth’s moon.
Trivia[]
- Pluto is the largest dwarf planet, with a diameter of 2.376.6 km while Eris is the most massive with a mass of 1.6×1022 kg. Ceres is also the smallest and least massive being 939.9 km in diameter and having a mass of 9.4×1020 kg
- Pluto is the first body to be classified as a dwarf planet after downgraded from a planet. Ceres and Eris came right after.
- Only 2 dwarf planets have been visited by space probes, they are Ceres and Pluto, although the others may be visited soon.
- Pluto was originally a planet until the creation of this group.
- Ceres is both an asteroid and a dwarf planet and is also the only dwarf planet in the Asteroid Belt, all the other dwarf planets are TNOs
- Haumea and Quaoar are the only dwarf planets that are known to have rings.
- Charon the largest moon of Pluto could be considered a dwarf planet, because Charon is spherical and the Pluto-Charon system is a binary system.
- Sedna is the furthest known dwarf planet candidate and has the highest eccentricity among the others, having an eccentricity of 0.85, it also created the category called sednoids.
Gallery[]
References[]
- ↑ https://www.iau.org/static/science/scientific_bodies/divisions/f/division-f-annual-report-2022-2023.pdf
- ↑ TRIENNIAL REPORT 2018-2021, written by Gonzalo Tancredi et al., 2021.