Kepler-7b (left), which is 1.5 times the radius of
Jupiter (right), is the first exoplanet to have its clouds mapped.
Image Credit: NASA/JPL-Caltech/MIT
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PASADENA, Calif. -- 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.
The planet is marked by high clouds in the west and clear skies in the east.
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, and Kepler-7b was one of the first. The telescope's problematic
reaction wheels prevent it from hunting planets any more, but astronomers
continue to pore over almost four years' worth of collected 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 were not enough on their own to decipher whether the bright spot was
coming from clouds or heat. 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 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 -- within 0.06 astronomical units (one astronomical unit is
the distance from Earth and the sun) -- 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 located on the west side of the
planet.
"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 an early step toward using similar techniques to study the
atmospheres of planets more like Earth in composition and size.
"With Spitzer and Kepler together, we have a multi-wavelength tool for
getting a good look at planets that are trillions of miles away," said Paul
Hertz, director of NASA's Astrophysics Division in Washington. "We're at a point
now in exoplanet science where we are moving beyond just detecting exoplanets,
and into the exciting science of understanding them."
Kepler identified planets by 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 just less
than five days.
Explore all 900-plus exoplanet discoveries with NASA's "Eyes on Exoplanets,"
a fully rendered 3D visualization tool, available for download at
The
program is updated daily with the latest findings from NASA's Kepler mission and
ground-based observatories around the world as they search for planets like our
own.
Other authors include: Julien de Wit, Nikole Lewis, Andras Zsom and Sara
Seager of Massachusetts Institute of Technology; Jonathan Fortney of the
University of California, Santa Cruz; Heather Knutson and Jean-Michel Desert of
the California Institute of Technology, Pasadena; Kevin Heng of the University
of Bern, Switzerland; Nikku Madhusudhan of Yale University, New Haven, Conn.;
Michael Gillon of the University of Liège, Belgium; Vivien Parmentier of the
French National Center for Scientific Research, France; and Nicolas Cowan of
Northwestern University, Evanston, Ill. Lewis is also a NASA Sagan Fellow.
The technical paper is online at
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space
Telescope mission for NASA. Science operations are conducted at the Spitzer
Science Center at Caltech. Data are archived at the Infrared Science Archive
housed at the Infrared Processing and Analysis Center at Caltech. Caltech
manages JPL for NASA. For more information about Spitzer, visit: http://spitzer.caltech.edu
and
Ames is responsible for Kepler's ground system development, mission
operations and science data analysis. JPL managed Kepler mission development.
Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler
flight system and supports mission operations with the Laboratory for
Atmospheric and Space Physics at the University of Colorado in Boulder. The
Space Telescope Science Institute in Baltimore archives, hosts and distributes
Kepler science data. Kepler is NASA's 10th Discovery Mission and was funded by
the agency's Science Mission Directorate. For more information about the Kepler
mission, visit:
and
NASA
Gguillermo Gonzalo Sánchez Achutegui
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