Home » Science & Nature » The Solar System » Will Pluto Lose its Planet Status?

Will Pluto Lose its Planet Status?

© Pattie Stechschulte

Believe it or not, the International Astronomical Union has never defined what a planet is, but recent and old discoveries may forced them to create one, leading to a reclassification of Pluto.

Many astronomers and scientist would like to classify the Pluto as a comet or part of the Kuiper Belt, which was discovered in 1992 and includes about 70 objects with similar orbits to Pluto, which is titled about 17 degrees from the other planets in the solar system.

There are no set scientific laws for planet classification, but scientists have always followed three general rules (according to NASA definition):
1. It must orbit a star;
2. It must be small enough that it has not be undergoing internal nuclear fusion (i.e. it is not a star or star-like object); and
3. It must be large enough that its self-gravity gives it the general shape of a sphere.

Last year, the Rose Center for Earth and Space at the American Museum of Natural History in New York opened a display of the solar system that did not include Pluto as a planet, but rather a comet. In a recent public statement about the display, Neil deGrasse Tyson, the planetarium's director, stated, "Instead of counting planets or declaring what is a planet and what is not, we organize the objects of the solar system into five broad families: the terrestrial planets, the Asteroid Belt, the Jovian planets, the Kuiper Belt and the Oort Cloud. With this approach, numbers do not matter and memorized facts about planets do not matter. What matters is an understanding of the structure and layout of the solar system."

Background and History

Astronomer Clyde Tombaugh discovered Pluto in 1930 as he doing research on Uranus at the Lowell Observatory. As it orbits, its distance to the sun varies between 2.8 to 4.5 billion miles. It is the smallest major planet, roughly half the size of Mercury and smaller than the Moon. Charon is Pluto's only moon and it is about half the size of the planet, appearing more like a double planet than a planet-moon. From 1979 to 1999, the planet's unusual orbit took Pluto inside Neptune's orbital path, making that planet the furthest planet in the system for 20 years.

One of the main reason astronomers would like to reclassify Pluto is because of its composition of a thick layer of water ice over a rocky core, with a surface coating mostly of frozen nitrogen, methane and water ice. It resembles a comet more than any of the other planets.

The copyright of the article Will Pluto Lose its Planet Status? in The Solar System is owned by Pattie Stechschulte. Permission to republish Will Pluto Lose its Planet Status? in print or online must be granted by the author in writing.