Earth is often referred to as the "blue planet," or "pale blue dot," due of course to the abundance of liquid water on its surface (about 70 percent is covered by water). But now astronomers have found another blue planet, and on this world, instead of water, it likely rains glass — and sideways at that, thanks to the planet's unfathomably strong 4,500 mile-per-hour winds. The gigantic, Jupiter-sized planet, designated HD 189733b, was actually first discovered by French astronomers in 2005. But recent observations made with NASA's Hubble Space Telescope have revealed far more fascinating details about its surface conditions and the color of its atmosphere.
Hubble is equipped with a specific instrument called a spectrograph that performs a prism-like effect (the light separating glass object, not the NSA program). The instrument is capable of distinguishing 500-different points in one exposure, so it's able to drill down into a faraway planet's atmosphere. In this case, Hubble's spectrograph recorded the light reflected off this planet as it passed behind its parent star, revealing that it scattered the color cobalt blue.
The color comes not from water like the blue hue here on Earth, but in this case, the planet's atmosphere. That atmosphere is basically "blow-torched," according to NASA, thanks to the planet's extremely close orbit to its parent star (2.9 million miles), and high surface temperature (around 2,000 degrees Fahrenheit). The atmosphere contains particles of silicate, the most abundant class of minerals on Earth, which scientists believe condense into glass on this planet, a result of the extreme heat. The glass then causes additional reflection of the blue color. Still, scientists have much to learn about this alternate blue world. "We obviously don't know much on the physics and climatology of silicate clouds, so we are exploring a new domain of atmospheric physics," said UK astronomer Frederic Pont, one of the scientists behind the new findings. The details appear in a paper published online today in the The Astrophysical Journal letters.