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Light from “super-Earth” reported seen for first time

May 9, 2012
Courtesy of NASA Jet Propulsion Laboratory
and World Science staff

NASA’s Spitzer Space Tel­e­scope has de­tected light from a “su­per-Earth” plan­et be­yond our so­lar sys­tem for the first time, as­tro­no­mers re­port.

While that hefty world isn’t thought to be hab­it­a­ble, sci­ent­ists call the achieve­ment a his­tor­ic step to­ward the search for signs of life on oth­er plan­ets. The Spitzer craft “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,” said Bill Danchi, Spitzer pro­gram sci­ent­ist at NASA Head­quar­ters in Wash­ing­ton.

As this artist's con­cept shows, a plan­et is hard to see in the glare of its par­ent star—when viewed in vis­i­ble light. But viewed in in­fra­red light, the plan­et stands out bet­ter. This is large­ly due to the fact that the plan­et's scorch­ing heat blaz­es with in­fra­red light. Even on our own bod­ies em­a­nate more in­fra­red light than vis­i­ble due to our heat. (Im­age cred­it: NA­SA/JPL-Caltech)


The plan­et, called 55 Can­cri e, falls in­to a class of plan­ets termed su­per Earths, which are heav­i­er than our home world but light­er than gi­ant plan­ets like Nep­tune. It’s about twice as big and eight times as mas­sive as Earth, and hugs its home star—55 Can­cri—in such a tight or­bit that its year lasts 18 hours.

Spitzer and oth­er tele­scopes pre­vi­ously stud­ied the world by an­a­lyz­ing how the light from 55 Can­cri changed as the plan­et passed in front of the star. In the new work, Spitzer meas­ured how much in­fra­red light comes from the plan­et it­self. 

In­fra­red is a type of low-energy light that we feel as heat but can­not see with our eyes. A plan­et is hard to see in the glare of its par­ent star when viewed in vis­i­ble light. But viewed with ca­mer­as that re­cord in­fra­red light, it stands out bet­ter.

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, re­search­ers said. The new da­ta, they added, fits 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 55 Can­cri sys­tem is fairly close to Earth, 41 light-years away (a light-year is the dis­tance light trav­els in a year). It has five plan­ets, with 55 Can­cri e the clos­est to the star and tid­ally locked—mean­ing one side al­ways faces the star, just as the Moon is tid­ally locked to Earth.

The Spitzer craft is full of surprises, said Mi­chael Wer­ner, Spitzer proj­ect sci­ent­ist at NASA’s Jet Pro­pul­sion Lab­o­r­a­to­ry in Pas­a­de­na, Ca­lif. “When we con­ceived of Spit­zer more than 40 years ago, exo­plan­ets [plan­ets out­side our so­lar sys­tem] had­n’t even been dis­cov­ered,” he noted.  “Be­cause Spitzer was built very well, it’s been able to adapt to this new field and make his­tor­ic ad­vanc­es such as this.”


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NASA’s Spitzer Space Telescope has detected light emanating from a “super-Earth” planet beyond our solar system for the first time, astronomers report. While the hefty world is not considered habitable, the achievement is seen as a historic step toward the eventual search for signs of life on other planets. The Spitzer craft “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,” said Bill Danchi, Spitzer program scientist at NASA Headquarters in Washington. The planet, called 55 Cancri e, falls into a class of planets termed super Earths, which are heavier than our home world but lighter than giant planets like Neptune. It’s about twice as big and eight times as massive as Earth, and hugs its home star—55 Cancri—in such a tight orbit that its year lasts 18 hours. Spitzer and other telescopes previously studied the world by analyzing how the light from 55 Cancri changed as the planet passed in front of the star. In the new work, Spitzer measured how much infrared light comes from the planet itself. Infrared is a type of low-energy light that we feel as heat but cannot see. 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, researchers said. The new data, they added, fits 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 55 Cancri system is fairly close to Earth, 41 light-years away (a light-year is the distance light travels in a year). It has five planets, with 55 Cancri e the closest to the star and tidally locked, meaning one side always faces the star, just as the Moon is tidally locked to Earth. “When we conceived of [the Spitzer telescope] 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.”