An exoplanet is a planet that orbits a star in another solar system – in other words, it has a different sun to us.
Exoplanets are a growing, and pretty exciting field of astrophysics. Scientists are looking to find as many of these planets as possible, to find out their size and distance from their suns. There’s a chance that they’ll find a ‘Goldilocks’ planet – a planet that’s ‘just right’ to support human life, and maybe already supports life of its own.
To find these planets, astrophysicists are using the Kepler probe. It’s basically a big light detector in space: it picks up the light from distant stars. If the light from the star varies in a certain way, that means that an orbiting planet has passed between Kepler and the star – i.e., there’s an exoplanet!
This method seems to be pretty efficient: here’s an image of the 1,235 objects that have been catalogued so far…
Awesome or what? Kepler looks at over 150,000 stars, searching for the tell-tale signs of a planet in transit. The astrophysicists can work out the planet’s size and distance from the star, and from that they can tell what kind of planet it is (a gas giant, like Jupiter, a hot desert rock like Mercury or maybe even an Earth-like planet) and what temperature it’s at, i.e. if it has liquid water, ice or steam at its surface. And that’s the clincher: to support life as we know it, a planet needs an oxygen-rich atmosphere with enough greenhouse gases to hold in the heat, and it needs to be kept at the right temperature to have water on the surface. Just like Baby Bear’s porridge.