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.

Toy "little green man" alien

Who knows – maybe little green men really exist! (And maybe they like sailing in lime boats, too!) Image: Foxymoron.

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…

All the exoplanets recorded in the first batch of data, arranged by the size of the star they orbit and shown in transit

This amazing image shows all 1,235 objects recorded in Kepler’s first batch of data, arranged by star size. The dark spots show each planet in transit across the front of their star. Image: Jason Rowe/Kepler

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.



  1. Pingback: The ‘Goldilocks planet’ search continues… « Jabberwacky

  2. Pingback: Signs of planets that are ‘just right’ may be wrong after all | Jabberwacky

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