Spitzer sees the light of alien 'super earth'

May 08, 2012
Super Earths are exotic planets unlike any in our solar system. They are more massive than Earth yet lighter than gas giants like Neptune, and they can be made of gas, rock or a combination of both. There are about 70 known to circle stars beyond our sun, and NASA's Kepler mission has detected hundreds of candidates. These planets' relatively small sizes make them very hard to see. Image credit: NASA/JPL-Caltech

(Phys.org) -- 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 and paving the way for NASA's upcoming to apply a similar technique on potentially ."

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 like Neptune. Fifty-five Cancri e is about twice as big and eight times as massive as Earth. The planet 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 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.

This plot of data from NASA's Spitzer Space Telescope reveals the light from a "super Earth" called 55 Cancri e. The planet is the smallest yet, beyond our solar system, to reveal its direct light. Super Earth's are more massive than Earth but lighter than gas giants like Neptune. While this planet is not habitable, the observations are an important milestone toward being able to eventually perform a similar technique on even smaller, potentially Earth-like planets. The plot shows how the infrared light from the 55 Cancri system, both the star and planet, changed as the planet passed behind its star in what is called an occultation. When the planet disappeared, the total light dropped, and then increased back to normal levels as the planet circled back into view. The drop indicated how much light came directly from the planet itself. This type of information is important for studying the temperatures and compositions of planetary atmospheres beyond our own. Image credit: NASA/JPL-Caltech/MIT

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 being 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 , 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 as 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 (JPL) 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 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.

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User comments : 16

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NickFun
1.2 / 5 (12) May 08, 2012
Though either side of the planet may be uninhabitable, there may be a "Goldilocks zone" where life is possible!
radek
1.2 / 5 (12) May 08, 2012
Though either side of the planet may be uninhabitable, there may be a "Goldilocks zone" where life is possible!


looks like habitable means human being can live there
Lurker2358
2 / 5 (15) May 08, 2012
2000 kelvin guys.

The surface of the planet is hotter than molten lava on Earth, or nearly 5 times hotter than Venus.
bluehigh
1.4 / 5 (14) May 08, 2012
Spitzer discovered the sun-facing side is extremely hot,


How so, if its tidally locked?

Spitzer would have to resolve better than about 8,000km over 41 ly and the window of opportunity would be a tiny fraction of the 18 hour orbit. Must rush the pineapples are calling.
Lurker2358
1 / 5 (10) May 08, 2012
I don't understand how they claim it is a water world, but it doesn't have an atmosphere.

How could a water world NOT have an atmosphere at such a high temperature?

Surface gravity should be almost exactly 2g, which is nowhere near enough to keep 2000k water in a liquid form, at least not without a heavy atmosphere crushing down on top of it. It could very well covered in hundreds or thousands of kilometers of water, but it should have an atmosphere of some kind...even if it's pure H20...
simplicio
5 / 5 (1) May 08, 2012
Surface gravity should be almost exactly 2g, which is nowhere near enough to keep 2000k water in a liquid form

It is not normal liquid water. The text says water is in a "supercritical" state where it is both liquid and gas.
Graeme
5 / 5 (1) May 08, 2012
The IR light curve does not sag off when the planet is edge on to us, so that probably means that the dark side is hot too, and that the atmosphere transfers heat. By averaging over many orbits perhaps a more accurate temperature map of the planet surface can be determined.
bluehigh
1 / 5 (13) May 09, 2012
How could a water world NOT have an atmosphere at such a high temperature?


de Bono would be proud of you with the realization that it doesn't and the prevailing interpretation is flawed.

At best this object is a big hot out-gassing asteroid like rock that has a short (astronomical) lifetime as it burns into the star 55 Cancri. Not a planet.
Vendicar_Decarian
5 / 5 (1) May 09, 2012
"How so, if its tidally locked?" - Bluehigh

Probably due to the lack of enhanced IR emissions as it passes in front of the star, as well as the shape of the light curve as the planet's IR radiation is extinguished and reacquired.
LordKinyambiss
1 / 5 (7) May 09, 2012
Spitzer's feats are truly Herculean in an astronomical sense. I certainly hope JWST will be able to detect molecules related to life, microbial or whatever else is on those near by potential habitat planets. If we see artificial compounds then we'll know that industrial revolutions are cosmic phenomena..
kevinrtrs
1.2 / 5 (17) May 09, 2012
Here the researchers might have an interesting conundrum:

1. It's a water planet - rocky center with water surrounding. Water is in supercritical state with a resulting blanketing plume.
2. The planet is tidally locked, meaning it's very close to the star, hence the extremely high temperature.

Question: How long has this planet been boiling it's water away and at what rate? How much water is there still left? How did this planet get "formed" with so much water on it and so near to the star - via the naturalistic nebular theory? How long has it been in existence given that the water is still there? Was the water there when it was first "formed"?

I guess the logical nebulous answer is that it migrated there from outside - though we cannot ever establish that this was the case.

bluehigh
1 / 5 (12) May 09, 2012
The IR emissions when this dying lump of rock is in front of the star would be obscured by the star itself. When behind the star we get no data. Nine hours remaining and light acquisition angles get almost insignificant. Guess work based on insufficient data but ... well done Spitzer for acquiring some (not quite useless) data.
Lurker2358
1 / 5 (9) May 09, 2012
It is not normal liquid water. The text says water is in a "supercritical" state where it is both liquid and gas.


Sorry, the "Critical point" for 2000K is going to be around 1000 Earth atmospheres, although it's off the scale of any phase diagram I could find, probably because you can't build a machine to actually test it.

Which means the planet still needs an atmosphere 5 times as thick as Venus per meter square surface (multiplied by 2g to get 1000 Earth atmosphere pressures).

Therefore, the scientists "findings" are self-contradictory.
Husky
not rated yet May 12, 2012
2g? it may be twice as big, but 8 times as massive as earth, try 8 g, but still trying to wrap my head around on how that would work
Vendicar_Decarian
5 / 5 (1) May 13, 2012
"try 8 g" - Husky

Mass goes to the third power of radius but given constant density, surface area goes to the second power of radius so gravitational pull at the surface is linear with radius.

Graeme
not rated yet May 16, 2012
If a water atmosphere is boiling away there whould be a lot of steam in that solar system. There should be water and hydroxyl absorption lines at temperatures lower than the star if this is happening.