One of the newest topic in astronomy presented at this year's NAM was the atmosphere's in exosolar planets session. I find it staggering that astronomers can now study the atmospheric composition of planets orbiting distant stars!

The ultimate aim is to find an atmosphere around a planet that could sustain life. That has not been found yet, but it is only a matter of time...

There are two ways to study the atmosphere of a distant exoplanet. If the planet ever passes in front of the parent star, some starlight is blocked by the planet itself, but some of the star-light is absorbed by the planet's atmosphere - and by looking at what wavelength's of starlight is absorbed by the planet's atmosphere, you can work out what chemicals are present in the planet's atmosphere. Also, when the planet moves around to the far side of the star, it can reflect starlight in our direction, and by looking at that reflected starlight astronomers can work our what chemicals are doing the reflection.

Doing this in reality is incredibly difficult, due to the parent star being so bright, and the planets being so small and faint.

An artist depicts the extrasolar planet, TrES-1, and its host star. Courtesy Jeffrey Hall and Lowell Observatory.

The highlight of the session was the research done by Tommi Koskinen at the University College London, on a planet called HD17156b. This planet was actually discovered by amateur astronomers! It is very impressive what new science can be achieved by experienced amateur astronomers. In this example, the planet moved in front of its parent star, hiding 0.6% of the light coming from the star - and this is enough for skilled amateur astronomers to detect the planet.

While amateurs monitor the entire sky, professionals scrutinise individual objects, and this is exact what Tommi and his colleagues have done. They discovered that the orbit of the planet around the parent star is very elliptical (strongly oval shaped), and so the temperature of the planet can vary by a staggering 1000oC depending on where it is in its orbit. They also discovered that when the planet is close to the star it rotates at the same rate at which it orbits, but when it is further away from the star it rotates quicker.