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Giant step in search for alien life
An artist’s impression of the planet called Osiris

London, Feb. 22: 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.

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 degrees Celsius — 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 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.

Similar conclusions are reached using the same data, analysed by a team led by Mark Swain at JPL.

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