On 9th October Dr Peter Wheatley (Warwick University) gave a super and wide-ranging talk on the topic of Extrasolar Planets at the FAS convention in Cambridge. He mentioned the 10cm Schmidt camera STARE which inspired the SuperWASP camera on the Canary Islands, which now has 8 200mm f/1.8 lenses and has discovered 26 exoplanets to date. SuperWASP uses the transit method which allows astronomers to weigh the planets and sometimes to determine their radii too, which together constrain theories for their internal structure. One of the current unsolved mysteries is how some hot Jupiters are so enlarged for their mass, more than can be explained by the super-heating received as the planet hovers over its parent star.
Another remarkable discovery is the planet HAT-P-7b which is in a retrograde orbit according to observations of the Rossiter-McLaughlin effect. Although some moons in our solar system (notably Triton) orbit in the "wrong" direction, it's difficult to imagine how a planet can move against the flow of a rotating protoplanetary disk.
Dr Wheatley showed a chart showing all known exoplanets, grouped according to their size and the distance from their host star. I produced my own version below using data from the Extrasolar Planet Encyclopedia. It's remarkable that we know almost 500 exoplanets now; in 1999 I read "Planet Quest" by the renowned science writer Ken Croswell, at which time only 9 were known! With Kepler and SuperWASP-2 in development, the thousandth exoplanet discovery is just around the corner!
Links
The SuperWASP homepage
Postscript
I plotted Gliese 581g, a very recent discovery currently generating much excitement due to its position within the zone of habitability around its parent star, where liquid water and therefore Earth-like life may exist. It's the 6th planet found orbiting Gliese 581, a rather cool red dwarf star in Libra.
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