Red dust in planet-forming disk may harbor precursors to life

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 1991generated 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.”

Source: Carnegie Institution

Related stories:

Planets by the Dozen
You know the planets of our solar system, each a unique world with its own distinctive appearance, size, and chemistry. Mars, with its bitter-cold, rusty red sands; Venus, a fiery world shrouded in thick clouds of sulfuric acid; sideways Uranus and its strange vertical rings. The variety is breathtaking.
Stellar Birth in the Galactic Wilderness
A new image from NASA's Galaxy Evolution Explorer shows baby stars sprouting in the backwoods of a galaxy -- a relatively desolate region of space more than 100,000 light-years from the galaxy's bustling center.
Catching planets in the making
For many years, astronomers have had a clear, though ever-evolving, picture of how planets are born. It starts with a disk of dust swirling around a newborn star, and then gradually the dust particles stick together to form ever-larger pieces--grains, pebbles, boulders, protoplanets and ultimately planets.
The Vanishing Rings of Saturn
Saturn: jewel of the solar system, taker of breaths, ringed beauty. Even veteran astronomers can't help but gasp when they see her through a small telescope. Red Alert: Saturn's rings are vanishing.
Spitzer Catches Young Stars in Their Baby Blanket of Dust
Newborn stars peek out from beneath their natal blanket of dust in this dynamic image of the Rho Ophiuchi dark cloud from NASA's Spitzer Space Telescope.
New Views of Martian Moons
These two images taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show Mars' two small moons, Phobos and Deimos, as seen from the Mars Reconnaissance Orbiter's low orbit around Mars. Both images were taken while the spacecraft was over Mars' night side, with the spacecraft turned off its normal nadir-viewing geometry to glimpse the moons.
Hubble sees the graceful dance of 2 interacting galaxies
A pair of galaxies, known collectively as Arp 87, is one of hundreds of interacting and merging galaxies known in our nearby Universe. Arp 87 was originally discovered and catalogued by astronomer Halton Arp in the 1970s. Arp’s Atlas of Peculiar Galaxies is a compilation of astronomical photographs using the Palomar 200-inch Hale and the 48-inch Samuel Oschin telescopes.
Arizona State scientists keep an eye on Martian dust storm
Scientists at Arizona State University's Mars Space Flight Center are using the Thermal Emission Imaging System (THEMIS) on NASA's Mars Odyssey orbiter to monitor a large dust storm on the Red Planet. The instrument, a multi-wavelength camera sensitive to five visible wavelengths and 10 infrared ones, is providing Mars scientists and spacecraft controllers with global maps that track how much atmospheric dust is obscuring the planet.

News discussion:

Space & Earth science news