(Photo: M. Kornmesser, NASA/ESA)
Dan Vergano, USA TODAY
Data from the Hubble space telescope has helped determine that a planet orbiting a nearby star likely shares Earth's deep-blue tones, but the similarities stop there, astronomers report.
The planet, HD 189733b, circles a star some 63 light years away, about 372 billion miles, according to the upcoming Astrophysical Journal Letters report led by the University of Oxford's Tom Evans. The Jupiter-sized planet, about 13% heftier than the largest planet in our solar system, orbits very close to its star, circling it once every 2.2 days. That makes it a (very) "Hot Jupiter" planet, the study notes, with cloud temperatures likely around 1,800 degrees Fahrenheit and winds whipping around at 4,350 miles-per-hour.
Astronomers have detected more than 800 "exoplanets" -- planets that orbit stars outside our solar system -- in the last two decades. HD 189733b was discovered in 2005.
The planet's clouds are likely blue, based on spectroscope data from Hubble, according to the international team of astronomers. The space telescope peered at the planet, before, during and after it was eclipsed by its star. That enabled the astronomers to subtract the light from the star from the light reflected off the planet, giving them a sense of its color.
"We saw the brightness of the whole system drop in the blue part of the spectrum when the planet passed behind its star," Evans says, in a statement. "From this, we can gather that the planet is blue, because the signal remained constant."
The team suggests the blue color likely comes from a hazy atmosphere filled with melting glass particles, ones that scatter blue light.
"It is by no means a giant step forward, but a nice observation with implications for clouds in this hot Jupiter's atmosphere, one of the key details for those who model the atmospheres of these hot planets," says planetary theorist Alan Boss of the Carnegie Institution of Washington, D.C. "It is amazing to think that we can now make measurements that tell us something about the cloud cover on distant exoplanets, and is especially amazing when we cannot even see these hot Jupiters directly."