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
http://eyes.nasa.gov/exoplanets.
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
http://www.mit.edu/~demory/preprints/kepler-7b_clouds.pdf .
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
http://www.nasa.gov/spitzer .
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:
http://www.nasa.gov/kepler and
http://www.kepler.nasa.gov .
Source:
ScienceDaily
