 On top of a volcano, on the island of La Palma, lives a curious looking creature called Superwosp. WASP stands for Wide Angle Search for Planets, but these are exoplanets. Planets outside our solar system, orbiting around distant stars. This is Superwosp. It's basically a lens, like a sports photographer would use, and underneath we have a camera. Maudenry Telescope would look at, if you're lucky, an area the size of the full moon. This sees an area a thousand times that. It's designed to look at a lot of sky and to measure the brightnesses of those stars with incredible accuracy. And so during the night we can get a record of how the star changes in brightness during the night. And if we're lucky we'll see a star change very slightly, it will kind of wink at you and it will do that if a large planet moves in front of it. Detecting a planet around a distant star isn't easy. Observing one directly would be like trying to spot a fly next to a floodlight. That's why astronomers have to employ clever alternative techniques to find such planets indirectly. If you imagine that this orange is a planet and this headlight is a star, then when the planet moves in front of the star you can see how the star gets fainted. That is exactly what super-wasp is trying to detect. Measuring the size of the dick in the light can tell astronomers how big the planet is relative to its parent star. But as the planet orbits around its star the force of gravity also causes the star to wobble slightly and by measuring this wobble astronomers can also calculate the mass of the planet relative to the star. Together the mass of the planet and the size of the planet gives us its density. So we can tell if we're dealing with a planet that is composed of gas because it will be very low density or a planet that is composed of rock which will be high density. Most of the more than 400 exoplanets astronomers have found so far are gas giants orbiting close to their parent star. They are called hot Jupiters and one is so close to its star that a year on that planet would last less than a day on Earth. If you're sitting on that planet you're in a very unusual place firstly it's incredibly hot but the other thing is that it's so incredibly close to its star the gravitational effect of that star will be so strong it's busy trying to tear the planet apart and so you would be subject to continual earthquakes. These hot giants are nothing like the Earth and incapable of sustaining life as we know it. Around every star is an area known as the habitable zone a place where it is neither too hot nor too cold for liquid water to form. Detecting a rocky earth-sized planet far enough from its star to lie in the habitable zone isn't easy but the longer we look and the better our telescopes get the closer we come to finding another Earth-like world. We should be able to discover a transit of an Earth-sized planet around a sunlight star within the next few years. The closest we may have come so far is a planet called Gliese 581C a rocky planet around six times the mass of the Earth orbiting its star within the habitable zone. Of course if we do find another Earth-like planet out there what we'll really want to know is whether it harbours life. One of the great things about the transiting planets is that during the transit the light of its star actually shines through its atmosphere so if we compare the light during the transit to the light outside of the transit the difference will tell us something about the atmosphere of that planet and we'll be able to look for signs of life in their atmospheres just like our atmosphere has. Each element in a planet's atmosphere will absorb specific wavelengths of the star's light meaning astronomers can look for signs of elements and compounds indicative of life such as water, oxygen and methane. I always think I'm one of the luckiest people in the world when I was a kid this was my hobby now I get paid to do it and I'm also doing something that was science fiction just 15 years ago. Sooner or later we're going to find planets that as far as we can tell will be able to sustain life and that will be a fantastic day for mankind we'll know that that we're not alone in the universe we may even learn something from them and they may come here and destroy us.