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Posted by baalke on October 12, 2006, 4:55 pm
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Oct. 12, 2006
Erica Hupp/Dwayne Brown
Headquarters, Washington
202-358-1237/1726
Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-4673
RELEASE: 06-334
NASA'S SPITZER SEES DAY AND NIGHT ON EXOTIC WORLD
NASA's Spitzer Space Telescope has made the first measurements of the
day and night temperatures of a planet outside our solar system. The
infrared observatory revealed that the Jupiter-like gas giant planet
circling very close to its sun is always as hot as fire on one side,
and potentially as cold as ice on the other.
"This planet has a giant hot spot in the hemisphere that faces the
star," said Joe Harrington of the University of Central Florida,
Orlando."The temperature difference between the day and night sides
tells about how energy flows in the planet's atmosphere. Essentially,
we're studying weather on an exotic planet."
The finding represents the first time any kind of variation has been
seen across the surface of an extrasolar planet, a planet beyond our
solar system. Previous measurements of extrasolar planets described
only global traits like size and mass.
"This is a spectacular result," said Michael Werner, project scientist
for Spitzer at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
"When we designed Spitzer years ago, we did not anticipate that it
would be revolutionizing extrasolar-planet science."
The researchers used Spitzer to determine the temperature variation in
the atmosphere of a nearby planet called Upsilon Andromedae b. This
"hot-Jupiter" planet is a gas giant similar to Jupiter, but it orbits
very close to its scorching star, circling the star once every 4.6
days.
Scientists believe the planet is tidally locked to its star. This
means it is rotating slowly enough that the same side always faces
the star, just as the same side of Earth's tidally locked moon always
faces toward us, hiding its "dark side." However, since this planet
is made of gas, its outer atmosphere could be circulating much faster
than its interior.
According to the astronomers, the observed temperature difference
between the two sides of Upsilon Andromedae b is extreme -- about
2,550 degrees Fahrenheit. Such a large temperature difference
indicates the planet's atmosphere absorbs and reradiates sunlight so
fast that gas circling around it cools off quickly. This is unlike
Jupiter, which is even-temperatured all the way around.
"If you were moving across the planet from the night side to day side,
the temperature jump would be equivalent to leaping into a volcano,"
said the project's principal investigator, Brad Hansen of the
University of California, Los Angeles.
Spitzer used its heat-seeking infrared eyes to periodically stare at
the Upsilon Andromedae planetary system over approximately five days.
It found the system's infrared light, or heat, dimmed and brightened
in time with Upsilon Andromedae b's orbit. This change in heat is the
result of the planet showing its different faces to Spitzer as it
traveled around the star. When the planet's sunlit side was in
Earth's view, Spitzer detected more heat from the system; when its
dark side was facing us, it picked up less heat. Upsilon Andromedae b
does not cross behind or in front of its star, but is always in
Earth's line of sight.
Upsilon Andromedae b was discovered in 1996 around the star Upsilon
Andromedae, which is 40 light-years away and visible to the naked eye
at night in the constellation Andromeda. Upsilon Andromedae is
circled by two other known planets located farther out than Upsilon
Andromedae b.
Harrington and Hansen are presenting their results today at the 38th
meeting of the Division for Planetary Sciences of the American
Astronomical Society in Pasadena, Calif. Harrington is lead author of
a paper appearing online today in Science.
The Jet Propulsion Laboratory 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, Pasadena.
For graphics about this research and more information about Spitzer,
visit:
http://www.nasa.gov/home
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