NASA’s Spitzer Sees the Light of Alien ‘Super Earth’

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News release: 2012-127 May 8, 2012

NASA's Spitzer Sees the Light of Alien 'Super Earth'

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2012-127&cid=release_2012-127

PASADENA, Calif. – NASA's Spitzer Space Telescope has detected light emanating from a "super-
Earth" planet beyond our solar system for the first time. While the planet is not habitable, the
detection is a historic step toward the eventual search for signs of life on other planets.

"Spitzer has amazed us yet again," said Bill Danchi, Spitzer program scientist at NASA Headquarters
in Washington. "The spacecraft is pioneering the study of atmospheres of distant planets and paving
the way for NASA's upcoming James Webb Space Telescope to apply a similar technique on
potentially habitable planets."

The planet, called 55 Cancri e, falls into a class of planets termed super Earths, which are more
massive than our home world but lighter than giant planets like Neptune. The planet is about twice as
big and eight times as massive as Earth. It orbits a bright star, called 55 Cancri, in a mere 18 hours.

Previously, Spitzer and other telescopes were able to study the planet by analyzing how the light from
55 Cancri changed as the planet passed in front of the star. In the new study, Spitzer measured how
much infrared light comes from the planet itself. The results reveal the planet is likely dark, and its
sun-facing side is more than 2,000 Kelvin (3,140 degrees Fahrenheit), hot enough to melt metal.

The new information is consistent with a prior theory that 55 Cancri e is a water world: a rocky core
surrounded by a layer of water in a "supercritical" state where it is both liquid and gas, and topped by
a blanket of steam.

"It could be very similar to Neptune, if you pulled Neptune in toward our sun and watched its
atmosphere boil away," said Michaël Gillon of Université de Liège in Belgium, principal investigator
of the research, which appears in the Astrophysical Journal. The lead author is Brice-Olivier Demory
of the Massachusetts Institute of Technology in Cambridge.

The 55 Cancri system is relatively close to Earth, at 41 light-years away. It has five planets, with 55
Cancri e the closest to the star and tidally locked, so one side always faces the star. Spitzer discovered
the sun-facing side is extremely hot, indicating the planet probably does not have a substantial
atmosphere to carry the sun's heat to the unlit side.

NASA's James Webb Space Telescope, scheduled to launch in 2018, likely will be able to learn even
more about the planet's composition. The telescope might be able to use a similar infrared method to
Spitzer to search other potentially habitable planets for signs of molecules possibly related to life.

"When we conceived of Spitzer more than 40 years ago, exoplanets hadn't even been discovered,"
said Michael Werner, Spitzer project scientist at NASA's Jet Propulsion Laboratory in Pasadena,
Calif. "Because Spitzer was built very well, it's been able to adapt to this new field and make historic
advances such as this."

In 2005, Spitzer became the first telescope to detect light from a planet beyond our solar system. To
the surprise of many, the observatory saw the infrared light of a "hot Jupiter," a gaseous planet much
larger than the solid 55 Cancri e. Since then, other telescopes, including NASA's Hubble and Kepler
space telescopes, have performed similar feats with gas giants using the same method.

In this method, a telescope gazes at a star as a planet circles behind it. When the planet disappears
from view, the light from the star system dips ever so slightly, but enough that astronomers can
determine how much light came from the planet itself. This information reveals the temperature of a
planet, and, in some cases, its atmospheric components. Most other current planet-hunting methods
obtain indirect measurements of a planet by observing its effects on the star.

During Spitzer's ongoing extended mission, steps were taken to enhance its unique ability to see
exoplanets, including 55 Cancri e. Those steps, which included changing the cycling of a heater and
using an instrument in a new way, led to improvements in how precisely the telescope points at
targets.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in
Washington. Science operations are conducted at the Spitzer Science Center at the California Institute
of Technology (Caltech) in Pasadena. 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://www.nasa.gov/spitzer and
http://spitzer.caltech.edu . More information about exoplanets and NASA's planet-finding program
is at http://planetquest.jpl.nasa.gov .

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