WHAT IS A PLANET?

Last updated:

USA Date: 02/17/2020

NZL Date: 17/02/2020

What is a planet? This is a fairly simple question! Growing up in school you learnt about planets like Earth, Venus and Mars. Even Pluto was considered a planet until in 2006 when the International Astronomical Union[IAU]classified it as a dwarf planet. So why change Pluto from a planet to a dwarf and what is the difference? 

First of all there are three main factors that make up a planet. The first is that a planet must orbit a star, in our case the Sun. Secondly, the planet must be big enough to have enough gravity to force it into a spherical shape. Thirdly, it must be big enough that its gravity clears away other objects of a similar size near its orbit around the Sun.

1.) It must orbit a star(like the Sun)

2.) It must be big enough to have enough gravity to force it into a spherical shape.

3.) It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun.

Planets are not only in our Solar System. There are other planets in other systems called Exoplanets. For more information, go to the "Exoplanet" page.

Images below-