Month: March 2009

Is Pluto a Planet?

Short answer – No, Pluto is no longer a Planet. It is a dwarf Planet.

It was originally classified as a planet, Pluto is now considered the largest member of a distinct population called the Kuiper belt. Pluto, considered a planet for 76 years, was reclassified as a dwarf planet in 2006.

What is a dwarf planet?

Pluto was found by Clyde W. Tombaugh in 1930. A dwarf planet, is a celestial body orbiting the Sun that is massive enough to be rounded by its own gravity but has not cleared its neighbouring region of planetesimals and is not a satellite. More explicitly, it has to have sufficient mass to overcome rigid body forces and achieve hydrostatic equilibrium.

What is a planet?

A planet is a large object such as Earth that orbits a star. It is smaller than a star, and it does not make light. Planets are ball-shaped (or spheres). Objects that orbit planets are called moons. Pluto used to be known as a planet, but in August 2006, a group of astronomers decided it should be called a dwarf planet instead. there are three main conditions for an object to be considered a ‘planet’:

1. The object must be in orbit around the Sun.
2. The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
3. It must have cleared the neighbourhood around its orbit.

Pluto meet the first two conditions, but failed to meet the third condition, hence it is not a Planet. You can learn more about Pluto here at the wikipedia.