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Thursday, October 21, 2010

New method for finding exoplanets

An international team of astronomers has successfully tested a novel way to find extrasolar or exoplanets. By using a special lens called an Apodizing Phase Plate (APP), they were able to cancel out the light of the star Beta Pictoris and directly see its planet Beta Pictoris b.

Caption: The planet Beta Pictoris b imaged using the Apodizing Phase Plate coronagraph. The "bad" (bright) side of the image is visible to the right while the central bright regions of the central star (Beta Pictoris) have been masked out to enable the viewer to clearly see the planet to the left of the star.

Credit: European Southern Observatory (ESO)

Close to 500 exoplanets (planets orbiting stars other than our sun) have already been discovered with more being found all the time. A variety of methods are used to find these planets, among them direct observation. However, in order to see a planet in the vicinity of its star, which may be a million times brighter than the planet, special lenses have to be employed. In the past, coronagraphs have been used to physically block starlight. These devices have to be lined up exactly right and are limited to detecting planets at least 30 astronomical units (about the distance from Neptune to the sun) from their stars.

Thanks to some complicated mathematics that I won’t even try to decipher, the new APP lens causes the light from the star to cancel itself out, leaving only the background visible. The astronomers were able to see Beta Pictoris b even though it’s only seven astronomical units from Beta Pictoris. This new method will make it easier to find Earth-like planets that might contain life.

Caption: The Apodizing Phase Plate causes light waves coming from a star to interfere with each other, exposing the faint glow of a nearby planet. Shown here is an early version.

Credit: University of Arizona