Dwarf Planets
Written by Abby Cessna
After Eris – a celestial body larger than Pluto – was discovered, the International Astronomy Union (IAU) reclassified Pluto. It was stripped of the label planet, which it had held for 76 years and, along with Eris, was named a dwarf planet. Despite what it sounds like, a dwarf planet is not simply a mini version of a planet, although dwarf planets are smaller than the planets in our solar system. The dwarf planet is a classification established by the IAU in 2006 in response to new discoveries.
The IAU's classification system did not meet with universal approval though. Many people were dissatisfied with reducing the number of planets to eight by reclassifing Pluto as well as disagreeing with the actual definition of the classifications.
In order to be classified as a planet, a celestial body has to orbit the Sun, have enough mass to overcome compression forces in order to form a sphere-like shape and have emptied its orbit of the significantly large celestial bodies. A dwarf planet is a non-satellite celestial body that meets all of the requirements for a planet except it shares its orbit with significantly large celestial bodies.
Scientists have identified at least five dwarf planets so far. In addition to Pluto and Eris, astronomers have labeled MakeMake, Haumea, and Ceres as dwarf planets. Astronomers think they will find as many as 2000 more dwarf planets in our solar system in the years to come. They have already identified forty objects that they are trying to prove fall into the category of dwarf planets.
The dwarf planets are located in various parts of the solar system, but most of them are in the Kuiper Belt, which is a region of space filled with icy celestial bodies called Kuiper Belt objects (KBOs). Pluto, Haumea, and MakeMake are all located in the Kuiper Belt. Ceres is located in the asteroid belt and Eris was discovered in the scattered disk, which is a region near the Kuiper Belt. Astronomers think that the Kuiper Belt is the most likely place to find more dwarf planets because of the size of KBOs.
None of the dwarf planets have been studied up close, but NASA's spacecraft New Horizons, which was launched in 2006, is scheduled to visit Pluto and other objects in the Kuiper Belt. Unfortunately, the probe will not reach that region until 2015, so astronomers and the rest of us will have to wait to discover more secrets about the dwarf planets.
Make sure you check out the following articles from Universe Today for more information on the dwarf planet Pluto and Pluto is no longer a planet.
Here are links to an article from NASA on the definition of a dwarf planet and one from Solstation on new dwarf planets.
Don't forget to tune into this episode of Astronomy Cast: how Pluto stopped being a planet.
Filed under: Astronomy
