Finally – a dream planet for meteorologists. Astronomers using data from NASA’s Kepler and Spitzer space telescopes have created the first cloud map ever of a planet beyond our solar system. Far away on Kepler-7b, clear skies dominate the planet’s eastern hemisphere while high clouds bedeck the west. Even I can forecast the weather working with those odds.
Kepler 7-b was one of the first five planets to be confirmed by the Kepler spacecraft. Orbiting just 5.6 million miles (9 million km) from its host star in the constellation Lyra, the planet sizzles with a surface temperature between 1,500 and 1,800 degrees F (815-980 degrees C). While that’s twice as hot as our solar system’s scorcher planet Venus, scientists were puzzled why Kepler-7b wasn’t even hotter given how close it is to its sun.
Kepler tracked the hot world through its moon-like phases for more than three years to create a rough map that showed a bright spot in its western hemisphere. Unsure as to whether the spot originated from clouds or the glow of intense heat, NASA swung the Spitzer Space Telescope around for a look. Even though it wasn’t designed to study exoplanets, it proved to be the perfect tool to solve the mystery of the white spot.
Spitzer studies celestial objects by the heat they radiate called infrared light. After three years of analysis, scientists determined that Kepler-7b’s temperature was too cool to be the source of the bright spot. Instead, a cloudy western hemisphere fit the data much better. Clouds are excellent reflectors of light; starlight bouncing from the planet’s cloud tops made sense.
“Kepler-7b reflects much more light than most giant planets we’ve found, which we attribute to clouds in the upper atmosphere,” said Thomas Barclay, Kepler scientist at NASA’s Ames Research Center in Moffett Field, Calif. “Unlike those on Earth, the cloud patterns on this planet do not seem to change much over time – it has a remarkably stable climate.”
Sadly, Kepler is no longer operational. One of its four reaction wheels, which keep the space telescope precisely pointed on a target, failed last July. When a second one failed in May, the scope was unable to continue its mission. Kepler needs a minimum of three wheels for accurate aiming.
We can be grateful for the more than 3,500 candidate planets the probe discovered during four years of useful life. They were all found by studying dips in a star’s brightness when a planet crossed or transited in front of it, blocking out a tiny portion of the light.
Just 151 of those planets have been confirmed, but scientists expect more 90 percent to be added to the roster once all the data’s crunched. Despite its unfortunate end, Kepler’s legacy will shine for years to come.