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“Cloud map” of planet beyond our system a first

Oct. 1, 2013
Courtesy of NASA Jet Propulsion Laboratory
and World Science staff

As­tro­no­mers us­ing da­ta from NASA’s Kep­ler and Spitzer space tele­scopes have cre­at­ed what they call the first cloud map of a plan­et be­yond our so­lar sys­tem. It’s a siz­zling, Ju­pi­ter-like world known as Kep­ler-7b.

High clouds in the west and clear skies in the east mark the plan­et, the map in­di­cates. Pre­vi­ous stud­ies from Spitzer have re­sulted in tem­per­a­ture maps of plan­ets or­bit­ing oth­er stars, but this is the first look at cloud struc­tures on a dis­tant world.

This diagram represents the cloud map of Kepler 7b, left, with Jupiter shown alongside for size comparison. (Image credit: NASA/JPL-Caltech/MIT)


“By ob­serv­ing this plan­et with Spit­zer and Kep­ler for more than three years, we were able to pro­duce a very low-re­so­lu­tion ‘map’ of this gi­ant, gas­e­ous plan­et,” said Brice-Oli­vier De­mory of Mas­sa­chu­setts In­sti­tute of Tech­nol­o­gy in Cam­bridge. 

He is the lead au­thor of a pa­per on the work, ac­cept­ed for pub­lica­t­ion in the jour­nal As­t­ro­phys­i­cal Jour­nal Let­ters

“We would­n’t ex­pect to see oceans or con­ti­nents on this type of world, but we de­tected a clear, re­flec­tive sig­na­ture that we in­ter­preted as clouds.”

Kep­ler has dis­cov­ered more than 150 exoplan­ets, which are plan­ets out­side our so­lar sys­tem. Kep­ler-7b, about 50 per­cent wid­er than Ju­pi­ter, was one of the first. The tel­e­scope is out of com­mis­sion for plan­et-hunting, but as­tro­no­mers are still por­ing over al­most four years’ worth of old da­ta.

Kep­ler’s visible-light ob­serva­t­ions of Kep­ler-7b’s moon-like phases led to a rough map of the plan­et that showed a bright spot on its west­ern hem­i­sphere. But these da­ta alone weren’t enough to de­ci­pher wheth­er the bright spot was com­ing from clouds or heat, ac­cord­ing to the as­tro­no­mers. The Spitzer tel­e­scope helped an­swer that.

Like Kep­ler, Spitzer can fix its gaze at a star sys­tem as a plan­et or­bits around the star, gath­er­ing clues about the plan­et’s at­mos­phere. Spitzer’s abil­ity to de­tect in­fra­red light, a low-energy form of light in­vis­i­ble to the un­aided eye, means it was able to meas­ure Kep­ler-7b’s tem­per­a­ture, es­ti­mat­ing it to be be­tween 1,500 and 1,800 de­grees Fahr­en­heit (1,100 and 1,300 Kelv­in). 

This is rel­a­tively cool for a plan­et that or­bits so close to its star – less than 1/15 as close to its sun as we are to ours – and ac­cord­ing to as­tro­no­mers, too cool to be the source of light Kep­ler ob­served. In­stead, they de­ter­mined, light from the plan­et’s star is bounc­ing off cloud tops on the plan­et’s west side.

“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.”

The find­ings are seen as an early step to­ward us­ing si­m­i­lar tech­niques to study the at­mos­pheres of plan­ets more like Earth in make­up and size.


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Astronomers using data from NASA’s Kepler and Spitzer space telescopes have created the first cloud map of a planet beyond our solar system, a sizzling, Jupiter-like world known as Kepler-7b. High clouds in the west and clear skies in the east mark the planet, the map indicates. Previous studies from Spitzer have resulted in temperature maps of planets orbiting other stars, but this is the first look at cloud structures on a distant world. “By observing this planet with Spitzer and Kepler for more than three years, we were able to produce a very low-resolution ‘map’ of this giant, gaseous planet,” said Brice-Olivier Demory of Massachusetts Institute of Technology in Cambridge. Demory is lead author of a paper accepted for publication in the Astrophysical Journal Letters. “We wouldn’t expect to see oceans or continents on this type of world, but we detected a clear, reflective signature that we interpreted as clouds.” Kepler has discovered more than 150 exoplanets, which are planets outside our solar system. Kepler-7b, about 50% wider than Jupiter, was one of the first. The telescope is out of commission for planet-hunting, but astronomers are still poring over almost four years’ worth of old data. Kepler’s visible-light observations of Kepler-7b’s moon-like phases led to a rough map of the planet that showed a bright spot on its western hemisphere. But these data alone weren’t enough to decipher whether the bright spot was coming from clouds or heat, according to the astronomers. The Spitzer Space Telescope played a crucial role in answering this question. Like Kepler, Spitzer can fix its gaze at a star system as a planet orbits around the star, gathering clues about the planet’s atmosphere. Spitzer’s ability to detect infrared light, a low-energy form of light invisible to the unaided eye, means it was able to measure Kepler-7b’s temperature, estimating it to be between 1,500 and 1,800 degrees Fahrenheit (1,100 and 1,300 Kelvin). This is relatively cool for a planet that orbits so close to its star – less than 1/15 as close to its sun as we are to ours – and according to astronomers, too cool to be the source of light Kepler observed. Instead, they determined, light from the planet’s star is bouncing off cloud tops on the planet’s west side. “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.” The findings are seen as an early step toward using similar techniques to study the atmospheres of planets more like Earth in makeup and size.