spacetoday.net: Astronomers find hot, windy exoplanets

Posted: Fri, May 11, 2007, 7:54 AM ET (1154 GMT)
HD 149026b exoplanet illustration (NASA/JPL-Caltech)

Scientists announced this week that they have found an extrasolar planet that is the hottest yet found, and another that may have extremely powerful winds. One team of astronomers used the Spitzer Space Telescope to measure the temperature of exoplanet HD 149026b by measuring the decrease in infrared light from the star system when the planet moved behind the star as seen from Earth. That data showed that the planet, smaller but more massive than Saturn, has a temperature of about 2,000 degrees Celsius, hotter than any other known planet. Astronomers suspect that the planet has an extremely low albedo, allowing it absorb nearly all the light from its star and giving it a black appearance. Another team of astronomers used Spitzer to construct a crude brightness map another exoplanet, HD 189733b. The found that the brightest spot on the planet was not at the sub-solar point but instead offset by 30 degrees, suggesting that strong winds were transferring heat in the planet's atmosphere. Computer models indicate that the winds could approach 10,000 km/h, about 30 times faster than the jet stream in the Earth's atmosphere.