Getting closer to detecting earth-size exoplanets

There is no reason to think why there won't be any earth-sized planets orbiting other stars. The detection techniques so far have been sensitive to the detection of large planets usually orbiting close to the parent star. We now have the detection of a solar system containing at least 5 Neptune-size planets - and may be two more planets, with at least one comparable to the size of the Earth (about 1.4 times the mass of the Earth). This system is located about 127 light years away and the host star is similar to the Sun. If you want to impress your friends, the name of the host star is HD 10180 (you can find details of the star and the planets if you click on the link to the name of the star).

Yes, this is very cool - especially if the detection of the smaller planet(s) is confirmed. However, couple of cautionary notes: This planetary system, despite all the planets, is quite different than our own solar system. The five Neptune-sized planets are all located within the distance of the orbit of Mars - and that makes it quite a bit crowded than the place we live in. Second, presence of the smaller planet(s) has not been confirmed yet (the detection technique does not involve images - rather, the presence of the planets is inferred from the slight wobble of the parent star - and model-fits to this wobble pattern. This is a very successful method of detecting planets, but as you can imagine, it also gets hard to infer the presence of small planets in a multi-planet system). And even if the detection of earth-size is confirmed, the planet may not be much like our own Earth as it is expected to be orbiting really really close to its sun - with a period of only 1.2 Earth-days! (For comparison, Mercury takes 88 days to around the Sun).

Nevertheless, we are getting closer to detecting earth-like planets. If you want to keep track of the number of extrasolar planets, you should check out The Extrasolar Planets Encyclopedia (488 planets from their count) and  Planet Quest (473 planets around 402 stars from their count). In fact, download this cool widget that will let you keep track of the count just like your computer clock and weather.

It is only a matter of time before we start detecting earth-like planets...

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