NASA's Spitzer sees the light of alien ‘Super-Earth’
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 towards
the eventual search for signs of life on other planets.
“Spitzer has amazed us yet again,” said Bill Danchi, Spitzer
programme 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.”
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An artist's concept shows, in visible light, a planet is lost in
the glare of its star (top view).
When viewed in infrared, the planet becomes brighter relative to
its star. This is largely due
to the fact that the planet's scorching heat blazes with
infrared light. Credit: NASA |
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 analysing 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 towards 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.
ScienceDaily |
