Grey Hautaluoma
Headquarters, Washington
202-358-0668
Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-4673
RELEASE: 07-109
NASA FINDS EXTREMELY HOT PLANET, MAKES FIRST EXOPLANET WEATHER MAP
WASHINGTON - Researchers using NASA's Spitzer Space Telescope have
learned what the weather is like on two distant, exotic worlds. One
team of astronomers used the infrared telescope to map temperature
variations over the surface of a giant, gas planet HD 189733b,
revealing it likely is whipped by roaring winds. Another team
determined that gas planet HD 149026b is the hottest yet discovered.
Both findings appear May 9 in Nature.
"We have mapped the temperature variations with longitude across the
entire surface of a planet that is so far away, its light takes 60
years to reach us," said Heather Knutson of the Harvard-Smithsonian
Center for Astrophysics in Cambridge, Mass., lead author of the paper
describing HD 189733b.
The two planets are "hot Jupiters" - sizzling, gas giant planets that
zip closely around their stars. Roughly 50 of the more than 200 known
planets outside our solar system, called exoplanets, are hot
Jupiters. Visible-light telescopes can detect these strange worlds
and determine certain characteristics, such as their sizes and
orbits, but not much is known about their atmospheres or what they
look like.
Since 2005, Spitzer has been revolutionizing the study of exoplanets'
atmospheres by examining their infrared light, or heat. In one of the
new studies, Spitzer set its infrared eyes on HD 189733b, located 60
light-years away in the constellation Vulpecula. HD 189733b is the
closest known transiting planet, which means that it crosses in front
and behind its star when viewed from Earth. It races around its star
every 2.2 days.
Spitzer measured the infrared light coming from the planet as it
circled around its star, revealing its different faces. These
infrared measurements, comprising about a quarter of a million data
points, were then assembled into pole-to-pole strips, and,
ultimately, used to map the temperature of the entire surface of the
cloudy, giant planet.
The observations reveal that temperatures on this balmy world are
fairly even, ranging from 1,200 F on the dark side to 1,700 F on the
sunlit side. HD 189733b, and all other hot Jupiters, are believed to
be tidally locked like our moon, so one side of the planet always
faces the star. Since the planet's overall temperature variation is
mild, scientists believe winds must be spreading the heat from its
permanently sunlit side around to its dark side. Such winds might
rage across the surface at up to 6,000 mph. The jet streams on Earth
travel at 200 mph.
"These hot Jupiter exoplanets are blasted by 20,000 times more energy
per second than Jupiter," said co-author David Charbonneau, also of
the Harvard-Smithsonian Center for Astrophysics. "Now we can see how
these planets deal with all that energy."
Also, HD 189733b has a warm spot 30 degrees east of "high noon," or
the point directly below the star. In other words, if the high-noon
point were in Seattle, the warm spot would be in Chicago. Assuming
the planet is tidally locked to its parent star, this implies that
fierce winds are blowing eastward.
In the second Spitzer study, astronomers led by Joseph Harrington of
the University of Central Florida in Orlando discovered that HD
149026b is a scorching 3,700 F, even hotter than some low-mass stars.
Spitzer was able to calculate the temperature of this transiting
planet by observing the drop in infrared light that occurs as it dips
behind its star.
"This planet is like a chunk of hot coal in space," said Harrington.
"Because this planet is so hot, we believe its heat is not being
spread around. The day side is very hot, and the night side is
probably much colder."
HD 149026b is located 279 light-years away in the constellation
Hercules. It is the smallest and densest known transiting planet,
with a size similar to Saturn's and a core suspected to be 70 to 90
times the mass of Earth. It speeds around its star every 2.9 days.
According to Harrington and his team, the oddball planet probably
reflects almost no starlight, instead absorbing all of the heat into
its fiery body. That means HD 149026b might be the blackest planet
known, in addition to the hottest.
"This planet is off the temperature scale that we expect for planets,"
said Drake Deming, a co-author of the paper, from NASA's Goddard
Space Flight Center, Greenbelt, Md.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the
Spitzer Space Telescope mission for NASA's Science Mission
Directorate, Washington. Science operations are conducted at the
Spitzer Science Center at the California Institute of Technology,
also in Pasadena.
For more information about the Spitzer Space Telescope, visit:
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