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"Long
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August 03, 2010
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Chemistry of other stars’ planets coming to light
Dec. 9, 2008
Courtesy NASA
and World Science staff
Carbon dioxide has been identified the atmosphere of a planet
outside our solar system, a key step toward finding chemical
signs of possible extraterrestrial life, astronomers say. An artist's impression of the planet HD 189733b behind and slightly beneath its parent star from our point of view. Astronomers using the Hubble Space Telescope have measured carbon dioxide and carbon monoxide in the planet's atmosphere. The planet is a "hot Jupiter," which is so close to its star that it completes an orbit in only 2.2 days. This type of observation is best done when the planet's orbit carries it behind the star (as seen from Earth), which allows an opportunity to subtract the light of the star alone (when the planet is blocked) from that of the star and planet together prior to eclipse, astronomers say. This allows astronomers to isolate the infrared emission of the planet and
chemically analyze the day-side atmosphere. (Credit: ESA, NASA, M. Kornmesser (ESA
The Jupiter-sized planet, called HD 189733b, is too hot for life. But the observations are a “proof of concept” that the basic chemistry of life is measurable on planets orbiting other stars, according to scientists.
On Earth, carbon dioxide is released when animals breathe. It and other carbon-based compounds can be byproducts of various life processes, so their detection on an Earth-like planet could someday provide the first evidence of life beyond Earth.
The researchers used NASA’s and the European Space Agency’s Hubble Space Telescope to search the light spectrum from the planet for telltale signatures of specific chemicals.
Previous observations of HD 189733b by Hubble and the Spitzer Space Telescope found water vapor. Earlier this year Hubble found methane in the planet’s atmosphere.
“Hubble is allowing us to see molecules that probe the conditions, chemistry, and composition of atmospheres on other planets,” said Mark Swain of The Jet Propulsion Laboratory in Pasadena,
Calif. “Thanks to Hubble we’re entering an era where we are rapidly going to expand the number of molecules we know about on other planets.”
Swain and other astronomers used an instrument on Hubble known as the Near Infrared Camera and Multi-Object Spectrometer to study infrared light emitted from the planet, which lies 63 light-years away. A light-year is the distance light travels in a year.
Identification of specific chemicals in celestial objects is possible because particular compounds absorb light of only certain energies. This leaves a mark on the light spectrum we see from that object: it’s devoid of light from those energies, or wavelengths. The team identified not only carbon dioxide, but also carbon monoxide.
“The carbon dioxide is kind of the main focus of the excitement, because that is a molecule that under the right circumstances could have a connection to biological activity as it does on Earth,” Swain said. “The very fact that we’re able to detect it, and estimate its abundance, is significant for the long-term effort of characterize planets both to find out what they’re made of and to find out if they could be a possible host for life.”
This type of observation is best done when the planet's orbit carries it behind
its host star, as seen from Earth, members of Swain’s team said. This provides
an opportunity to subtract the light of the star alone, when the planet is
blocked, from that of the star and planet together prior to eclipse. This
in turn allows astronomers to isolate the infrared light of the planet.
The findings are to appear in an upcoming issue of The Astrophysical
Journal.
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Carbon dioxide has been identified the atmosphere of a planet orbiting another star, a key step toward finding chemical tracers of possible extraterrestrial life, astronomers say. The Jupiter-sized planet, called HD 189733b, is too hot for life. But the observations are a “proof of concept” that the basic chemistry of life is measurable on planets orbiting other stars, according to scientists. On Earth, carbon dioxide is released when animals breathe. It and other carbon-based compounds can be byproducts of various life processes, so their detection on an Earth-like planet could someday provide the first evidence of life beyond Earth. The researchers used the Hubble Space Telescope to search the light spectrum from the planet for telltale signatures of specific chemicals. Previous observations of HD 189733b by Hubble and the Spitzer Space Telescope found water vapor. Earlier this year Hubble found methane in the planet’s atmosphere. “Hubble is allowing us to see molecules that probe the conditions, chemistry, and composition of atmospheres on other planets,” said Mark Swain of The Jet Propulsion Laboratory in Pasadena, Calif., a member of the research team. “Thanks to Hubble we’re entering an era where we are rapidly going to expand the number of molecules we know about on other planets.” The international team of astronomers used an instrument on Hubble known as the Near Infrared Camera and Multi-Object Spectrometer to study infrared light emitted from the planet, which lies 63 light-years away. A light-year is the distance light travels in a year. Identification of specific chemicals in celestial objects is possible because particular compounds absorb light of only certain energies. This leaves a mark on the light spectrum we see from that object: it’s devoid of light from those energies, or wavelengths. The team identified not only carbon dioxide, but also carbon monoxide. “The carbon dioxide is kind of the main focus of the excitement, because that is a molecule that under the right circumstances could have a connection to biological activity as it does on Earth,” Swain said. “The very fact that we’re able to detect it, and estimate its abundance, is significant for the long-term effort of characterizing planets both to find out what they’re made of and to find out if they could be a possible host for life.”