The Hubble Space Telescope has identified the true visible-light color of a giant Jupiter-sized planet located 63 light-years away and found it to be cobalt blue. Unlike our blue planet Earth, whose color comes from our world’s oceans, the blue color of planet HD 189733b doesn’t come from water. Instead, the cobalt blue color is believed to come from torrential 4,500-mile-per-hour winds blowing across the surface of this world, which are so hot that they melt silicates into raindrops of sideways-blowing molten glass.
The planet orbits the yellow-orange star HD 189733. It’s one of the closest exoplanets – or planets orbiting distant suns – that can be seen crossing the face of its star.
Winds blowing across the surface of this world are thought to be so hot they melt silicates into raindrops of molten glass, which blow sideways across this world’s surface. The cobalt-blue color of the planet seen from afar comes from these melted glass raindrops, which scatter blue light more readily than green or red light.
The planet’s color provides unique clues to the atmosphere and weather on a truly alien world that orbits much closer to its star than the innermost planet Mercury is to our sun.
Bottom line: Earth appears blue from space because it has oceans. Planet HD 189733b appears blue because of molten glass “raindrops” blowing sideways across its surface!
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.