Building blocks of life found around star HR 4796A

William Atkins
Tuesday, 08 January 2008 19:42

Science - Space

Earth no longer contains tholins because oxygen deletes them very rapidly. However, it is assumed that tholins were present in the early formation of the Earth, before oxygen came so abundant on our planet.

The study was published in Astrophysical Journal Letters. In the paper that was submitted to arXiv.org (“Complex Organic Materials in the Circumstellar Disk of HR 4796A”), the authors—John H. Debes, A.J. Weinberber, and G. Schneider—state in their abstract:

“We combine HST/NICMOS imaging photometry of the HR 4796A disk at previously unobserved wavelengths between 1.71-2.22\micron with reprocessed archival observations to produce a measure of the dust's scattering efficiency as a function of wavelength. The spectrum of the dust, synthesized from the seven photometric measures, is characterized by a steep red slope increasing from 0.5 \micron to 1.6 \micron followed by a flattening of the spectrum at wavelengths $>$ 1.6 \micron. We fit the spectrum with a model population of dust grains made of tholins, materials comprised of complex organic materials seen throughout the outer parts of our Solar System. The presence of organic material around a star that may be in the later stages of giant planet formation implies that the basic building blocks for life may be common in planetary systems.”
HR 4796A is a young star located in the constellation Centaurus. It is about eight million years old and is about 220 light-years from our solar system. HR 4796A is about twice as large as our Sun and about twenty times more bright than it. Its protoplanetary dust disk (a rotating disk of dense gas surrounding a young newly formed star) was discovered in 1991, and is considered a good example of a planetary system in formation.

The dust cloud around stars was formed by collisions of small bodies. Comets and asteroids probably came from such dust clouds. It is possible that comets and asteroids hitting our planet early in its formation, helped to bring life to our planet.