Dwarf Planets by Lily Toto 5/23/13

Our solar system is massive, containing many different things. There are the planets, the sun, meteoroids, comets, and dwarf planets. Dwarf planets are very different from other planets. For something to be considered a planet, it must be in orbit around the sun, have enough mass and gravity to give it a nearly round shape, and have cleared its neighborhood. Dwarf planets fit the first two criteria, but not the third. Dwarf planets are objects which are in orbit around the sun, are nearly round in shape, but have not cleared their neighborhood. 

The five known dwarf planets. Image from http://the-mysterious-universe.blogspot.com/2011/09/dwarf-planet.html

Dwarf planets have been discovered in two places in our solar system. One place, where the majority of dwarf planets have been detected, is the Kuiper Belt, a vast region of our solar system beyond the orbit of Neptune. The other place where a dwarf planet has been found is the Asteroid Belt, an area between Mars and Jupiter. There is only one known dwarf planet in the Asteroid Belt. The total amount of dwarf planets in our solar system is unknown, but so far astronomers have recognized only five. These five are called Pluto, Ceres, Eris, Makemake, and Haumea.

This map of our solar system shows the locations of the Asteroid Belt and Kuiper Belt. Image from http://awcase.hubpages.com/hub/spacey#slide1507864

The most well-known dwarf planet is Pluto. Pluto is the second largest dwarf planet, as well as the 10th largest body orbiting our sun. It was originally thought to be a planet, but later was recognized as a dwarf planet because it hasn't cleared its neighborhood. Pluto is mainly composed of rock and ice. Pluto’s surface has many colored patches on it. The bright areas of its surface are thought to be covered with ices composed of nitrogen, ethane, methane, and carbon monoxide. The composition of the darker areas on Pluto is unknown, but may be caused by organic material on its surface. Pluto also has 3 moons. The largest is called Charon, and the two smaller ones are called Hydra and Nix. As Pluto is extremely far from the sun, 3,670,050,000 miles away, it is very cold. Its temperatures vary from -235 to -210 C.

Pluto and its moons, Charon, Hydra, and Nix. Image from http://xenopandora.deviantart.com/art/Pluto-and-Its-Moons-251846414

Ceres is the only known dwarf planet in the asteroid belt,  the region of the Solar System located between the orbits of the planets Mars and Jupiter. It’s also the smallest known dwarf planet. The surface of Ceres is assumed to be a mixture of water, ice, and various hydrated minerals such as carbonates and clays. Ceres appears to contain a rocky inner core and a mantle composed of water and ice. Ceres might even have an ocean of liquid water underneath its surface, inside of the icy mantle. Ceres is very cold, although it isn’t as cold as Pluto, and has a maximum temperature of −38 °C.

Ceres has very interesting layers. Image from https://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29

Eris is the largest dwarf planet and the ninth largest body in our solar system, and is located in the Kuiper Belt. It has one moon, Dysnomia. Eris has a grey surface. Eris is usually so far from the sun, it’s 97 times further from the sun than Earth, that its atmosphere collapses and freezes on the surface in an icy glaze. Its temperature varies from about -217 degrees Celsius to -243 degrees Celsius, depending on where it is in its orbit. Under the ice, Eris is thought to be rocky, much like Pluto.

Eris and its moon, Dysnomia. Image from http://apod.nasa.gov/apod/ap070619.html

Makemake is another dwarf planet, and it is located in the Kuiper Belt. It’s red in color. This is thought to be the result of tholins. Tholins are substances which form as a result of the interaction between ultraviolet light and certain substances. Makemake is the only dwarf planet in the Kuiper Belt that has no moons or satellites orbiting it. Scientists believe there is frozen ethane and methane on Makemake's surface and have also discovered evidence of frozen nitrogen. Like Eris, Makemake does not have a significant atmosphere.

Makemake. Image from http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level1/makemake.html

Haumea is unique among the dwarf planets, especially in shape. It isn’t a sphere, but is instead an ellipsoid. The reason for its odd shape lies in its extremely fast rotation, Haumea takes only four Earth hours to complete a full rotation. It spins so fast that it has been stretched out.  Haumea is very dense, which has led scientists to believe that its surface is covered in rock. Haumea also has two known satellites, moons called Hi'iaka and Namaka.

Haumea and its two moons, Hi’iake and Namaka. Image from http://en.wikipedia.org/wiki/Haumea_%28dwarf_planet%29

            For more information and facts about our solar system’s dwarf planets, click this link : http://www.windows2universe.org/our_solar_system/dwarf_planets/dwarf_planets.html