[concentric circles]

Found: one Earth-like planet - Nature 1/25/06
Astronomers use gravity lensing to spot homely planets.

"...More than 170 planets have been discovered outside our Solar System. Astronomers usually detect them by watching how they make their parent star wiggle, a technique known as the Doppler method. This is ideal if you are looking for massive planets orbiting very close to their star, which induce a lot of wobble."

"But there is no way this can be used to find small, blue-green planets approximately 150 million kilometres from a yellow sun. It is simply not sensitive enough, says Didier Queloz, an astronomer from Geneva Observatory in Switzerland who was part of the team that found the first extrasolar planet, just 11 years ago."

"The new sighting relies on an effect called gravitational lensing, where a massive object such as a star warps space so that it behaves like a lens. This means that it bends and slightly magnifies light from a more distant star before it reaches our telescopes. Adding a planet to the mix modifies the lensing effect by a tiny amount, just enough to work out its mass and orbit..."

[Verginius Rufus]

Astronomers use gravity lensing to spot homely planets.

I'm really impressed that their telescopes are so good that they can distinguish homely planets from good-looking ones at that distance.

[IYAAYAS]

But there is no way this can be used to find small, blue-green planets approximately 150 million kilometres from a yellow sun
I doubt this is true. We just don't have enough dynamic sensitivity in the instruments, assuming space is continuous.

[lmr]

Astronomers usually detect them by watching how they make their parent star wiggle, a technique known as the Doppler method.

These planets aren't actually seen, they are 'detected' by the gravitational forces that are present in a system. These planets are hence 'inferred' to be there. Could there be other things causing the 'wobble" like other stars or black holes or something?