• Question: What are exoplanets like? What is their atmosphere like?

    Asked by Harrysimp710 to Stefan, Rob on 12 Nov 2014.
    • Photo: Rob Appleyard

      Rob Appleyard answered on 12 Nov 2014:

      We don’t know the whole answer to this yet, but it will depend on the planet. Some planets in our solar system, like Mercury, have almost no atmosphere. Some planets, like Jupiter, are made of almost nothing but atmosphere. It’s likely planets outside our solar system are just as different.

    • Photo: Stefan Lines

      Stefan Lines answered on 12 Nov 2014:

      You will have noticed that in our Solar System, there is great diversity. We have the rocky or ‘terrestrial’ planets such as Mercury, Earth and Mars. Of these some have barely any atmosphere (Mercury), some have a toxic atmosphere (Venus) and some have an ideal atmosphere for life (Earth). Then we have the Gas Giants like Jupiter. It is thought they were once rocky planets like us, but got so big they started to pull gas onto them – although it’s amazing to think we’re still not quite sure whether they have a rocky core inside (still need someone to answer this). Then you have the Ice Giants like Neptune. Oh… and then also the Dwarf Planets like Pluto and Sedna!

      In that case, it probably doesn’t come as a surprise if I say that Exoplanets also come in great diversity. We see different planets to our own too, like massive Jupiter like planets that orbit closer to their sun than us. That makes them really hot. So we gave them the boring and obvious name… hot jupiters. We’ve found planets that rotate at 90,000km/h (Beta Pictoris b) which means it has a day in just 8 hours. We’ve found planets in binary systems too (Kepler-34b).

      We are often able to measure the mass of the planet, as well as its radius – which means we can calulate the density – and determine if it is rocky or gas like. The problem is probing their atmospheres. We don’t know so much about this. But it’s a big area of research. We have telescopes being built that will be able to tell us much more about this in the next decade.

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