Light from Exoplanets Detected |
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Written by spacetravel.org
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Two independent teams of astronomers announced on March 22, 2005 that, using the Spitzer Space Telescope, they had detected light from two exoplanets orbiting close to two stars. Both of these exoplanets, HD209458b and TrES-1, had been discovered previously, and had been found to transit the discs of their stars as seen from Earth. Using Spitzer, astronomers compared the amount of infrared light that was observable when both star and planet were visible with the amount of observable infrared light when the planet was behind the star. They calculated the difference in observable infrared light to be the light produced by the planet.
The studies used infrared, rather than visible light, because of the differences in relative brightness between the planet and the star. With visible light, the glare of the star completely overwhelms any light reflected by the planet. The planet emits its own infrared light, however, so the contrast between the star and the planet is more favorable.
Astronomers can use information about the light coming from these planets to learn about these planetsÂ’ characteristics. They have discovered that both planets have temperatures of at least 1,000 Kelvins, and believe that they can learn about their atmospheres as well.
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