Precursor of life molecules found around star

By Andrea Thompson

updated 4:02 p.m. ET Jan. 7, 2008

Astronomers have found the first signature of complex organic molecules in the dust cloud around a distant star, suggesting that these building blocks of life may be a common feature of planetary systems.

In our solar 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 are thought to be precursors to the biomolecules that make up living organisms on Earth (though they are no longer found on our planet because the oxygen in our atmosphere would quickly destroy them).

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

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

"Until recently it's been hard to know what makes up the dust in a disk from scattered light, so to find tholins this way represents a great leap in our understanding," said study team member John Debes of the Carnegie Institution.

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

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

Because the star is twice as massive and nearly twice as hot as the sun, it provides clues into the different conditions under which planets, and life, might potentially evolve.

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