On 17/10/2012 2:20 PM, wrote:
I'd like to know why they have just found a planet at Alpha Centauri,
our nearest star, when they have been searching the skies for years
and have found 600 or so planets (iirc). it must've been the first
place they looked, mustn't it? Strikes me as odd.

Most of the 1000's of exoplanets found so far have been discovered by
Kepler. Kepler only looks for planets by the Transit Method, which when
you get right down to it, is the easiest method of detecting planets.
Before Kepler, we used the Wobble Method. The Wobble Method uses Doppler
shifts to determine if a planet is tugging on a star. It works really
well when the planets are really massive and/or very close in to their
stars. Smaller planets are harder to detect using this method. We
couldn't use the Transit Method like with Kepler because this star
system doesn't seem to be aligned to our line of sight. Also Kepler
probably doesn't even point in the direction of this star system.

So our only hope was to find a planet with the Wobble method, which as I
said before, is better at detecting Big planets. But they've refined the
Wobble Method, and it can detect far smaller planets now. It's much
harder to detect planets with the Wobble method, but it can detect
planets that aren't perfectly aligned with our line of sight.

Yousuf Khan