Astronomers using the Hubble Space Telescope have surmised the color of another planet beyond our solar system. HD 189733b’s azure blue globe resembles Earth from afar but don’t be fooled. This is a frightening place.
The scorching hot, Jupiter-sized world orbits a faint star 63 light years from the sun in the summer constellation Vulpecula; it’s one of the nearest exoplanets observed to transit or cross the face of its host star. If you could somehow survive a descent through its 1,800 F (1000 C) atmosphere, you’d better batten down the hatches. Howling winds of 4,350 mph (7000 km/hr) fling fine particles of searing glass sideways through the fiery air.
This planet makes Hades feel like a pleasant summer afternoon. Blame its hot temperament on a tight orbit – only 2.8 million miles separate HD 189733 b from its host star. Our local hothead Mercury orbits almost 13 times farther from the sun. Day- and night-side temperatures differ by about 500 degrees F (260 C) at HD 89733b, causing fierce winds to roar across the planet.
Astronomers measured the light of the planet-star system before, during and after the planet passed in front of the star as it orbited. Once the planet disappeared behind the star, not only did the light of the whole system drop slightly, but the overall color balance changed. Instruments on Hubble recorded a decrease in the amount of blue light.
You can guess where the blue went – out of view with the planet. Earth’s blue hue comes from the atmosphere and oceans, but HD 189733b draws its color from a hazy, turbulent atmosphere rich with silicate (rock, glass) particles which scatter blue light.