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This illustration shows one possible scenario for the hot, rocky
exoplanet called 55 Cancri e, which is nearly two times as wide as
Earth. Image credit: NASA/JPL-Caltec.› Full image and caption
The varying brightness of an exoplanet called 55 Cancri e is shown in
this plot of infrared data captured by NASA's Spitzer Space Telescope.
Image credit: NASA/JPL-Caltech/University of Cambridge.› Full image and caption
This animated illustration shows one possible scenario for the rocky
exoplanet 55 Cancri e, nearly two times the size of Earth. New Spitzer
data show that one side of the planet is much hotter than the other -
which could be explained by a possible presence of lava pools. Credit:
NASA/JPL-Caltech.› Larger image
Observations from NASA's Spitzer Space Telescope have led to the
first temperature map of a super-Earth planet -- a rocky planet nearly
two times as big as ours. The map reveals extreme temperature swings
from one side of the planet to the other, and hints that a possible
reason for this is the presence of lava flows.
"Our view of this planet keeps evolving," said Brice Olivier Demory
of the University of Cambridge, England, lead author of a new report
appearing in the March 30 issue of the journal Nature. "The latest
findings tell us the planet has hot nights and significantly hotter
days. This indicates the planet inefficiently transports heat around the
planet. We propose this could be explained by an atmosphere that would
exist only on the day side of the planet, or by lava flows at the planet
The toasty super-Earth 55 Cancri e is relatively close to Earth at 40
light-years away. It orbits very close to its star, whipping around it
every 18 hours. Because of the planet's proximity to the star, it is
tidally locked by gravity just as our moon is to Earth. That means one
side of 55 Cancri, referred to as the day side, is always cooking under
the intense heat of its star, while the night side remains in the dark
and is much cooler.
"Spitzer observed the phases of 55 Cancri e, similar to the phases of
the moon as seen from the Earth. We were able to observe the first,
last quarters, new and full phases of this small exoplanet," said
Demory. "In return, these observations helped us build a map of the
planet. This map informs us which regions are hot on the planet."
Spitzer stared at the planet with its infrared vision for a total of
80 hours, watching it orbit all the way around its star multiple times.
These data allowed scientists to map temperature changes across the
entire planet. To their surprise, they found a dramatic temperature
difference of 2340 degrees Fahrenheit (1,300 Kelvin) from one side of
the planet to the other. The hottest side is nearly 4,400 degrees
Fahrenheit (2,700 Kelvin), and the coolest is 2,060 degrees Fahrenheit
The fact Spitzer found the night side to be significantly colder than
the day side means heat is not being distributed around the planet very
well. The data argues against the notion that a thick atmosphere and
winds are moving heat around the planet as previously thought. Instead,
the findings suggest a planet devoid of a massive atmosphere, and
possibly hint at a lava world where the lava would become hardened on
the night side and unable to transport heat.
"The day side could possibly have rivers of lava and big pools of
extremely hot magma, but we think the night side would have solidified
lava flows like those found in Hawaii," said Michael Gillon, University
of Liège, Belgium.
The Spitzer data also revealed the hottest spot on the planet has
shifted over a bit from where it was expected to be: directly under the
blazing star. This shift either indicates some degree of heat
recirculation confined to the day side, or points to surface features
with extremely high temperatures, such as lava flows.
Additional observations, including from NASA's upcoming James Webb
Space Telescope, will help to confirm the true nature of 55 Cancri e.
The new Spitzer observations of 55 Cancri are more detailed thanks to
the telescope's increased sensitivity to exoplanets. Over the past
several years, scientists and engineers have figured out new ways to
enhance Spitzer's ability to measure changes in the brightness of
exoplanet systems. One method involves precisely characterizing
Spitzer's detectors, specifically measuring "the sweet spot" -- a single
pixel on the detector -- which was determined to be optimal for
"By understanding the characteristics of the instrument -- and using
novel calibration techniques of a small region of a single pixel -- we
are attempting to eke out every bit of science possible from a detector
that was not designed for this type of high-precision observation," said
Jessica Krick of NASA's Spitzer Space Science Center, at the California
Institute of Technology in Pasadena.
NASA's Jet Propulsion Laboratory in Pasadena, California, manages the
Spitzer Space Telescope mission for NASA's Science Mission Directorate,
Washington. Science operations are conducted at the Spitzer Science
Center. Spacecraft operations are based at Lockheed Martin Space Systems
Company, Littleton, Colorado. Data are archived at the Infrared Science
Archive housed at the Infrared Processing and Analysis Center at
Caltech. Caltech manages JPL for NASA.