One way to find extrasolar planets is to look for the slight dimming that occurs when such a planet crosses the path of its star. This method is known as ‘the transit method’. The planets found by this method have tended to be extremely large. Not the type of planet on which one would expect to find life. Now, an international group of astronomers led by Gracjan Maciejewski of Jena University in Germany, have used a variation of the transit method to find Earth-sized planets.
The new technique is called the Transit Timing Variation, or TTV. So far the team has used it to detect a new planet in the star system called WASP-3. That system contains a previously discovered planet known as WASP-3b, a gas giant with 630 times the mass of the Earth. With TTV, the astronomers carefully measure slight deviations in the transit time of WASP-3b across its star. Those tiny deviations are caused by another, much smaller planet, which is exerting a pull on WASP-3b. The new planet, with about 15 times the mass of the Earth, was duly dubbed WASP-3c.
This is the first time this method has been used. WASP-3c is one of the smallest exoplanets found to date, leading astronomers to hope that TTV can be used to find even smaller and thus more Earth-like planets.