For images and captions, see

http://www.ciw.edu/news/red_dust_planet_forming_disk_may_harbor_precursors_life

For Immediate Release January 3, 2008

Contact:

John Debes
1-202-478-8862, debes@dtm.ciw.edu

PIO Source:

Alan Cutler
1-202-939-1142
acutler@ciw.edu

For copies of the paper go to http://arxiv.org/abs/0712.3283

Red Dust in Planet-Forming Disk May Harbor Precursors to Life

Washington, DC - Astronomers at the Carnegie Institution have found the first
indications of highly complex organic molecules in the disk of red dust
surrounding a distant star. The eight-million-year-old star, known as HR 4796A,
is inferred to be in the late stages of planet formation, suggesting that the
basic building blocks of life may be common in planetary systems.

In a study published in the current Astrophysical Journal Letters, John Debes
and Alycia Weinberger of the Carnegie Institution’s Department of Terrestrial
Magnetism with Glenn Schneider of the University of Arizona report observations
of infrared light from HR 4796A using the Near-Infrared Multi-Object
Spectrometer aboard the Hubble Space Telescope. The researchers found that the
spectrum of visible and infrared light scattered by the star’s dust disk looks
very red, the color produced by large organic carbon molecules called tholins.
The spectrum does not match those of other red substances, such as iron oxide.

Tholins do not form naturally on present-day Earth because oxygen in the
atmosphere would quickly destroy them, but they are hypothesized to have existed
on the primitive Earth billions of years ago and may have been precursors to the
biomolecules that make up living organisms. Tholins have been detected elsewhere
in the solar system, such as in comets and on Saturn’s moon Titan, where they
give the atmosphere a red tinge. This study is the first report of tholins
outside the solar system.

"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," says Debes.

HR 4796A is located in the constellation Centaurus, visible primarily form the
southern hemisphere. It is about 220 light years from Earth. The discovery of
its dust disk in 1991 generated excitement among astronomers, who consider it a
prime example of a planetary system caught in the act of formation. The dust is
generated by collisions of small bodies, perhaps similar to the comets or
asteroids in our solar system, and which may be coated by the organics. These
planetesimals can deliver these building blocks for life to any planets that may
also be circling the star.

"Astronomers are just beginning to look for planets around stars much different
from the Sun. HR 4796A is twice as massive, nearly twice as hot as the sun, and
twenty times more luminous than the Sun," says Debes. "Studying this system
provides new clues to understanding the different conditions under which planets
form and, perhaps, life can evolve."

This research is based on observations with the NASA/ESA Hubble Space Telescope
and was supported by NASA and the NASA Astrobiology Institute.

The Carnegie Institution (www.CIW.edu) has been a pioneering force in basic
scientific research since 1902. It is a private, nonprofit organization with six
research departments throughout the U.S. Carnegie scientists are leaders in
plant biology, developmental biology, astronomy, materials science, global
ecology, and Earth and planetary science.