The new Solar System

Our knowledge of the Solar System and planets in general has changed dramatically over recent years. The field of planetary science is currently going through a revolution!

You might think of the Solar System as 4 terrestrial planets, 4 Jovians, Pluto, dozens of satellites, thousands of asteroids, and possibly millions of comets. But lately things have been getting a bit confusing. For example, planetary scientists will tell you there are three clear groups of planets: the terrestrial, gas giants (Jupiter and Saturn), and ice giants (Uranus and Neptune) – though ice giants are a sub-class of gas giants. Some asteroids have comet-like coma (like 2060 Chiron) and as we’ve seen hundreds of new objects are being found orbiting the Sun out past Neptune.

Added to this, over 350 extrasolar planets have been found, none of which look much at all like our Solar System. Many stars seem to host “hot Jupiters” – Jupiter mass planets on extremely short periods (ten times closer to their host star than Mercury is to the Sun), and most planets seem to be on eccentric orbits.

And if you thought all this wasn’t bad enough, free floating “planets” have been found in the Orion star forming region – surely a planet has to at least orbit a star? So with all this new information, there are strong arguments for defining exactly what a planet is. Let’s have a look at the debate about defining planets in more detail.