Nasa closer to discovering life on other planets
By Roger Highfield, Science Editor
21/02/2007
Astronomers have captured enough light from two planets far beyond our own solar system to reveal details of their chemical make-up, marking a new phase in the search for extraterrestrial life.
An artist's impression of a cloudy Jupiter-like planet, like the one analysed using the Spitzer Space Telescope
By analysing the faint glow of one of these alien worlds they have found tentative evidence that suggests the presence of chemicals which play a role in one theory of how life began on Earth.
The chemicals, polycyclic aromatic hydrocarbons, may have helped the formation of RNA, the ancestral genetic material of DNA, the building-blocks of life on our own planet.
Although this planet seems to lack water and is at a searing 800 C - which is thought to be much too hot for life - three teams announce today they have successfully carried out the feat on this and one other alien world, marking a breakthrough in the development of techniques capable of scouring the cosmos for signs of life.
The research builds on earlier work with the Hubble Space Telescope which detected sodium, hydrogen and carbon from starlight passing through the atmosphere of the planet with polycyclic aromatic hydrocarbons and shows that it is possible to measure the chemical make-up of "extrasolar" planets - those outside our solar system - and to hunt for the chemical markers of life in the far-flung reaches of space.
Of the 200 alien planets (those outside our Solar System) so far detected in the 20 billion planetary systems estimated to be in our galaxy alone, 14 pass in front of their parent stars of which two are bright enough to be analysed by the new method, which reveals the signatures of particles and gases present in a planet's spectrum, like fingerprints.
By reading these fingerprints, researchers can learn about an atmosphere's composition and even deduce the presence of clouds, perhaps even the presence of life - if it comes in a form that we can recognise.
Jeremy Richardson of the NASA Goddard Space Flight Centre in Greenbelt, Maryland, and colleagues describe today in the journal Nature how they have obtained the infrared spectrum of the extrasolar planet, HD 209458b, nicknamed Osiris, which orbits a Sun like star in the constellation Pegasus using the Spitzer Space Telescope, a £400 million instrument launched in 2003.
Similar conclusions are reached using the same data, analysed by a team led by Mark Swain at JPL. And another spectrum is reported by Carl Grillmair of the Spitzer Science Centre Caltech and colleagues who studied another exoplanet, HD 189733b. This is a technical tour de force because light from the parent stars swamps the relatively dim glow of the planets.
Working with Drake Deming, Karen Horning, Sara Seager and Joseph Harrington, Richardson observed the infra red light spectrum of the planet and parent star together before the planet passed behind the star, and again whilst it was hidden behind the star.
By subtracting their measurements during these two three-hour long eclipses, they were able to infer the planet's own rainbow like spectrum, even though it took the light around 150 years to reach the Spitzer. Because the spectrum contains lines corresponding to where chemicals absorb or emit light, forming dark and bright bands, they can probe the conditions of its atmosphere.
The planet is a so called "hot Jupiter," that is a gas giant like our own Jupiter, but orbiting much closer to its parent star, some 10 times closer than Mercury is to our Sun. Calculations of what the spectrum of such a planet would look like if it contained water vapour do not fit today's measurements, suggesting it is dry, or that the vapour is hidden under thick clouds.
The planet seems to contain silicate dust at high altitudes, according to one broad emission peak, a mineral common on Earth and in our Solar System. There is also an unidentified feature in the spectrum, a much sharper peak at a wavelength of around 7.78 micrometres, which is hard to identify but may correspond to polycyclic aromatic hyrocarbons, or PACs, ("a more exotic possibility"), and what the team says are "several other suggestive features."
Another planet, known as HD 189733b. was studied in a similar way by a team led by Grillmair.
"In a sense, we're getting our first sniffs of air from an alien world," said his colleague David Charbonneau of the Harvard-Smithsonian Centre for Astrophysics.
And what we found surprised us. Or more accurately, what we DIDN'T find surprised us."
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Alien planet facts
By Roger Highfield, Science Editor
21/02/2007
• The exosolar planets - that is, planets which lie beyond our own Solar System - were studied by the Spitzer Space Telescope, a £400 million instrument launched in 2003.
• Neither of the parent stars for HD 209458b or HD 189733b can be seen with the naked eye.
• Spitzer revealed that HD 209458b and HD 189733b had no water in the tops of their atmospheres, a finding which surprised astronomers.
• HD 209458b, nicknamed Osiris, is a "hot Jupiter" that orbits a Sun like star in the constellation Pegasus and bakes at 800 deg C
• HD 189733b is another hot, cloudy Jupiter-like planet, having a mass 365 times that of the Earth and a radius 14 times larger. Its density is comparable to that of Saturn.
• HD 209458b is located about 153 light-years away in the constellation Pegasus, while HD 189733b is about 62 light-years away in the constellation Vulpecula.
• One light year - the distance light covers in one year - is equivalent to 5.9 million million miles.
• Both planets zip around their stars in very tight orbits; HD 209458b circles once every 3.5 days, while HD 189733b orbits once every 2.2 days.
• Of the more than 200 known exoplanets, there are 12 besides HD 209458b and HD 189733b whose orbits are inclined in such a way that, from our point of view, they pass in front of their stars.
telegraph.co.uk
By Roger Highfield, Science Editor
21/02/2007
Astronomers have captured enough light from two planets far beyond our own solar system to reveal details of their chemical make-up, marking a new phase in the search for extraterrestrial life.
An artist's impression of a cloudy Jupiter-like planet, like the one analysed using the Spitzer Space Telescope
By analysing the faint glow of one of these alien worlds they have found tentative evidence that suggests the presence of chemicals which play a role in one theory of how life began on Earth.
The chemicals, polycyclic aromatic hydrocarbons, may have helped the formation of RNA, the ancestral genetic material of DNA, the building-blocks of life on our own planet.
Although this planet seems to lack water and is at a searing 800 C - which is thought to be much too hot for life - three teams announce today they have successfully carried out the feat on this and one other alien world, marking a breakthrough in the development of techniques capable of scouring the cosmos for signs of life.
The research builds on earlier work with the Hubble Space Telescope which detected sodium, hydrogen and carbon from starlight passing through the atmosphere of the planet with polycyclic aromatic hydrocarbons and shows that it is possible to measure the chemical make-up of "extrasolar" planets - those outside our solar system - and to hunt for the chemical markers of life in the far-flung reaches of space.
Of the 200 alien planets (those outside our Solar System) so far detected in the 20 billion planetary systems estimated to be in our galaxy alone, 14 pass in front of their parent stars of which two are bright enough to be analysed by the new method, which reveals the signatures of particles and gases present in a planet's spectrum, like fingerprints.
By reading these fingerprints, researchers can learn about an atmosphere's composition and even deduce the presence of clouds, perhaps even the presence of life - if it comes in a form that we can recognise.
Jeremy Richardson of the NASA Goddard Space Flight Centre in Greenbelt, Maryland, and colleagues describe today in the journal Nature how they have obtained the infrared spectrum of the extrasolar planet, HD 209458b, nicknamed Osiris, which orbits a Sun like star in the constellation Pegasus using the Spitzer Space Telescope, a £400 million instrument launched in 2003.
Similar conclusions are reached using the same data, analysed by a team led by Mark Swain at JPL. And another spectrum is reported by Carl Grillmair of the Spitzer Science Centre Caltech and colleagues who studied another exoplanet, HD 189733b. This is a technical tour de force because light from the parent stars swamps the relatively dim glow of the planets.
Working with Drake Deming, Karen Horning, Sara Seager and Joseph Harrington, Richardson observed the infra red light spectrum of the planet and parent star together before the planet passed behind the star, and again whilst it was hidden behind the star.
By subtracting their measurements during these two three-hour long eclipses, they were able to infer the planet's own rainbow like spectrum, even though it took the light around 150 years to reach the Spitzer. Because the spectrum contains lines corresponding to where chemicals absorb or emit light, forming dark and bright bands, they can probe the conditions of its atmosphere.
The planet is a so called "hot Jupiter," that is a gas giant like our own Jupiter, but orbiting much closer to its parent star, some 10 times closer than Mercury is to our Sun. Calculations of what the spectrum of such a planet would look like if it contained water vapour do not fit today's measurements, suggesting it is dry, or that the vapour is hidden under thick clouds.
The planet seems to contain silicate dust at high altitudes, according to one broad emission peak, a mineral common on Earth and in our Solar System. There is also an unidentified feature in the spectrum, a much sharper peak at a wavelength of around 7.78 micrometres, which is hard to identify but may correspond to polycyclic aromatic hyrocarbons, or PACs, ("a more exotic possibility"), and what the team says are "several other suggestive features."
Another planet, known as HD 189733b. was studied in a similar way by a team led by Grillmair.
"In a sense, we're getting our first sniffs of air from an alien world," said his colleague David Charbonneau of the Harvard-Smithsonian Centre for Astrophysics.
And what we found surprised us. Or more accurately, what we DIDN'T find surprised us."
----------------------------------------------
Alien planet facts
By Roger Highfield, Science Editor
21/02/2007
• The exosolar planets - that is, planets which lie beyond our own Solar System - were studied by the Spitzer Space Telescope, a £400 million instrument launched in 2003.
• Neither of the parent stars for HD 209458b or HD 189733b can be seen with the naked eye.
• Spitzer revealed that HD 209458b and HD 189733b had no water in the tops of their atmospheres, a finding which surprised astronomers.
• HD 209458b, nicknamed Osiris, is a "hot Jupiter" that orbits a Sun like star in the constellation Pegasus and bakes at 800 deg C
• HD 189733b is another hot, cloudy Jupiter-like planet, having a mass 365 times that of the Earth and a radius 14 times larger. Its density is comparable to that of Saturn.
• HD 209458b is located about 153 light-years away in the constellation Pegasus, while HD 189733b is about 62 light-years away in the constellation Vulpecula.
• One light year - the distance light covers in one year - is equivalent to 5.9 million million miles.
• Both planets zip around their stars in very tight orbits; HD 209458b circles once every 3.5 days, while HD 189733b orbits once every 2.2 days.
• Of the more than 200 known exoplanets, there are 12 besides HD 209458b and HD 189733b whose orbits are inclined in such a way that, from our point of view, they pass in front of their stars.
telegraph.co.uk
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