spacetoday.net: Astronomers determine color of exoplanet

Astronomers determine color of exoplanet

Posted: Fri, Jul 12, 2013, 8:24 AM ET (1224 GMT)
Blue HD 189733b exoplanet illustration (ESA/NASA)

Astronomers for the first time have measured the color of an extrasolar planet, finding that it is a primarily blue world but for reasons very unlike Earth. Astronomers used the Hubble Space Telescope to take spectra of the exoplanet HD 189733b as it passed behind its star. Astronomers noticed a slight decrease in blue light when the planet was hidden from view, but no significant change in green or red light. Astronomers conclude that the planet is predominantly blue in color. The planet is a hot Jupiter, and that blue color likely comes from silicate particles in clouds in its upper atmosphere that preferentially scatter blue light.