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Small, cool planet found (27/01/2006)
The planet was discovered using a new technique called gravitational microlensing. Until now, planets were spotted by the way their gravitational pull makes their host star wobble, a technique which uses the Doppler effect (see Plus article Brave young worlds). But for this to work, the planet has to be massive enough or close enough to its star to exert the necessary pull. Consequently, all planets found so far are much more massive than OGLE-2005-BLG-390Lb.
Gravitational microlensing uses a different approach: as a star passes in front of a more distant reference object, its gravity acts like a lense and increases the object's brightness for a period of a few weeks. If the moving star has a companion planet, then this gives the brightness an extra spark. Although this is the third exoplanet discovered using gravitational microlensing, it's the first one of such low mass. Scientists think that these small worlds are much more common in the universe than was previously assumed. To find out more and see some pictures read this article from the European Southern Observatory.
posted by Plus @ 2:11 PM