Building blocks of life found around star HR 4796A

William Atkins
Tuesday, 08 January 2008 18:42

Science - Space

A new U.S. study has found complex organic molecules, tholins, in the dust cloud around the star HR 4796A. The important conclusion of these researchers is that this discovery provides good evidence that living organisms are common throughout planetary systems.            

Tholins (from a Greek word for muddy) are heteropolymers (polymers made up of more than one polymer) formed by solar ultraviolet irradiation from simple organic compounds such as methane.

In the atmosphere, tholins act as a protective screen for ultraviolet radiation, helping to protect the planet below them. On the surface of planets, they allow bacteria within soil to use carbon as their food. Tholins give planetary surfaces their reddish-brown color.

Telescopes, such as the NASA Hubble Space Telescope (HST), have been used to discover these large carbon molecules called tholins in comets, on Titan, a moon of Saturn, and Triton, a moon of Neptune. For instance, the atmospheres around Triton and Titan are almost entirely made up of nitrogen, with small amounts of methane and other trace gases.

In this study, astronomers found the “first” sign of complex organic molecules—what scientists call the precursors to biomolecules that make up living organisms—around a star, specifically within the dust cloud around the star HR 4796A.

Astronomers found tholins around the star HR 4796A because the spectrum of scattered visible and infrared radiation (light) from the star, along with other celestial bodies, appears orange-red to brown-red, a color that is known to come from tholins.

The researchers used the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) aboard the Hubble Space Telescope to discover the reddish spectrum of tholins around the star.

In this study the astronomers suggest that these building blocks of life may be a common feature of planetary systems. This statement is very important to astronomers and scientists in general in their search for life in the universe.