EUROPEAN planet hunters are stealing a march on their American rivals. After last week鈥檚 discovery of a 鈥渉abitable鈥� extrasolar planet the mass of five Earths 鈥� the smallest yet found 鈥� European astronomers have had more good news. Their new space telescope, called COROT, is proving 10 times as sensitive as expected. The spacecraft seems sharp enough to detect planets as small as Earth, a task widely thought impossible in advance of the launch of NASA鈥檚 Kepler telescope in October 2008.
The realisation came as astronomers analysed the first data beamed back from COROT, which launched on 27 December 2006. 鈥淲e are no longer talking about just detecting super-Earths,鈥� says Malcolm Fridlund, COROT mission scientist at the European Space Agency (ESA). 鈥淲e are talking about detecting Earths.鈥�
When an exoplanet passes in front of its parent star, it causes a subtle dimming in the light reaching us 鈥� a dimming COROT鈥檚 sensitive detectors are designed to spot. After 60 days of initial observations, two possible planets stood out strongly in the raw data. A follow-up campaign of observations from ground-based telescopes across Europe showed that one of these candidates was indeed a planet. Weighing in at 1.3 Jupiter masses, it was whipping around a host star of 1.17 solar masses in just 1.5 days. The other object was a previously unknown red dwarf star in orbit around a larger, yellow star.
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鈥淭he big news is that by doing this we got our first estimates of the instrument鈥檚 capability,鈥� says Fridlund. And the news is very good. Even before removing contaminating 鈥渂ackground鈥� light that fell into the telescope and correcting for the blur in the image caused by jitters in the apparatus, COROT exceeded all expectations. By the time the team has created the software to enable these final refinements in data, Fridlund says COROT may be performing up to 30 times better than its design specification.
The project is headed up by the French national space agency, CNES, with partners including ESA, which supplied the telescope鈥檚 optics and tested it on the ground prior to launch. During its three-year mission, COROT will monitor tens of thousands of stars. Working at its newly estimated sensitivity, it should easily find Earth-sized worlds in the habitable zone of red dwarf stars, with orbital periods of about a fortnight.
鈥淲orking at its new sensitivity, COROT should easily find Earth-sized worlds in the habitable zone of red dwarf stars.鈥�
The team, which includes astronomers from Europe and Brazil, is hurrying to develop new software to process raw COROT data automatically. If they are successful, the telescope could bag its first Earth-sized world later this year.
