Precursor of Life Molecules Found Around Star

Astronomershave found the first signature of complex organic molecules in the dust cloudaround a distant star, suggesting that these building blocks of life may be acommon feature of planetary systems.

In oursolar system, the large carbon molecules, called tholins,have been found in comets and on Saturn's moon, Titan,giving its atmosphere a red tinge.

Tholins arethought to be precursors to the biomolecules that make up living organisms onEarth (though they are no longer found on our planet because the oxygen in ouratmosphere would quickly destroy them).

A new study,detailed in a recent issue of Astrophysical Journal Letters, features observationsof the spectrum of the dust disk surrounding the star HR4796A that indicate thepresence of tholins there.

Thespectrum of scattered visible and infrared light from the disk looks very red,the researchers report, a color known to be produced by tholins. (Thespectrum's signature doesn't seem to match other red substances, such as ironoxides.)

"Untilrecently it's been hard to know what makes up the dust in a disk from scatteredlight, so to find tholins this way represents a great leap in ourunderstanding," said study team member John Debes of the CarnegieInstitution.

HR4796A,located in the constellation Centaurus, is a massive 8-million-year-old starabout 220 light-years from Earth. Its dust disk, discovered in 1991, isconsidered a prime example of a planetary system in formation.

The dust isgenerated by the collisions of small bodies, perhaps similar to our own comets and asteroids, which coulddeliver these tholins to planets that might be orbiting the distant star.

Because thestar is twice as massive and nearly twice as hot as the sun, it provides cluesinto the different conditions under which planets, and life, might potentiallyevolve.

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