Earlier observations from NASA's Hubble Space Telescope found evidence of blue light scattering from the planet, and recent measurements from Hubble's Imaging Spectrograph confirmed that the planet is indeed blue.
But the blue is not a reflection of water, as it is on Earth. Rather, the cobalt color is the result of hazy, high clouds full of silicate particles essentially "blow-torched" in the atmosphere.
HD 189733b is only 2.9 million miles from its star, so close it is gravitationally locked, meaning one side always faces the star. Day side and night side temperatures can differ by about 500 degrees Fahrenheit, causing fierce winds.
On this planet, day side temperatures can reach nearly 2,000 degrees Fahrenheit. Silicates condensing in the heat could form very small drops of glass that rain, possibly sideways in 4,500-mph winds.
Hubble and other observatories studying HD 189733b have found its turbulent atmosphere to be "changeable and exotic."
The planet belongs to an unusual class known as "hot Jupiters," which orbit precariously close to their stars. Researchers say these findings can help explain the the chemical compositions and cloud structures of the entire class.