Exoplanet Cloud Atlas

Patchy Clouds on a Distant World

Even though it’s not doing any more planet-searching due to an equipment failure, the Kepler telescope (along with the Spitzer Space Telescope) have returned data about a distant exoplanet called Kepler-7b that show it has clouds in its atmosphere. The data allowed astronomers to create an atlas of cloud forms over this planet, ranging from high clouds and clear skies in the western to somewhat clearer regions elsewhere. This is the first time that a “reflective signature” (that is, data that indicate reflectivity of an object in space) has been seen.

Kepler-7b planet radiates much more heat than most giant planets that Kepler scientists have found and its reflectance definitely implies clouds. It lies much too far away from its star to account for the light scientists see being reflected by the planet. That almost certainly suggest that there are clouds floating in this world’s upper atmosphere.

During its mission, Kepler identified planets by fixing its gaze at a specific point in the sky and watching for dips in starlight that occur as the planets transit, or pass in front of their stars, blocking the light. This technique and other observations of Kepler-7b previously revealed that it is one of the puffiest planets known. If it could somehow be placed in a tub of water, it would float. The planet was also found to whip around its star in slightly less than five days, giving it a very short year.

Kepler’s partner in the observations of Kepler-7b, the Spitzer Space Telescope, can focus on one part of the sky for long periods of time, just as Kepler was designed to do. Spitzer is sensitive to infrared light which means it can “see” the heat coming from a distant object and take its temperature. During its observation, Kepler detected a temperature for Kepler-7b somewhere between 1,500 and 1,800 degrees Fahrenheit. Much hotter than most household ovens.

Using the two of these telescopes together to observe distant worlds gives astronomers a new way to study planets that lie far away circling other stars. It also allows astronomers to fine-tune their search for clouds on smaller, Earth-like worlds. (If you’re interested in more details you can read more about this discovery here.)

Now that Kepler is no longer actively looking for planets, scientists are turning their attention to the immense amount of data Kepler sent back, and using telescopes such as Spitzer (and ground-based instruments) to do observations on already known planet candidates.

I find it amazing that we can see these clouds on such a distant world (it lies trillions of miles from Earth). But, I find really impressive is that even though Spitzer can no longer do the most sensitive observations (due to its losing its instrument coolant), it can definitely still show us some amazing things in the cosmos. There are many more planet candidates discovered by Kepler that scientists will be studying, so look for more Kepler-based announcements in the foreseeable future.