viernes, 23 de julio de 2010
Buckyballs Found in Space
The discovery of these carbon structures in space could have a profound impact on our understanding of chemistry in the cosmos.
Scientists have found crystalline forms of carbon -- spheres comprised of 60- and 70-atom clusters -- in a planetary nebula.
Carbon in this form is known as a buckminsterfullerene and was discovered in 1985.
Buckyballs and related spherical cages of carbon molecules sired the field of nanotechnology.
Twenty-five years after the discovery of buckyballs, the 60-packs of carbon molecules are found again -- this time in space, baked into the death shroud of a sun-like star.
The finding promises to open new doors in astronomy, just as the 1985 discovery of the third form of solid carbon (after diamond and graphite) revolutionized chemistry, leading to new materials built one stable molecule at a time.
The buckyballs were found in a planetary nebula called Tc 1, located about 6,000 light-years away. These types of nebula are shells of gas and dust shed by dying stars. In the case of Tc 1, the star, now a white dwarf, is still encased, but not quite dead.
Astronomers believe that as recently as 100 years ago, the star had another outburst. Its layers of hydrogen, however, already had been shed, leaving it with a helium shell and carbon-rich core.
"For a lot of planetary nebulae, that may be an end stage. But then the helium shell started burning, and it shed carbon-rich and hydrogen-poor material," lead researcher Jan Cami with the University of Western Ontario in Canada told Discovery News.
That turned out to be an ideal environment for cooling carbon atoms to cluster into their most stable form, 60-atom molecules shaped like soccer balls, known as buckyballs.
Cami and colleagues found the molecules by looking at Tc 1's infrared emissions with NASA's Spitzer Space Telescope.
When light hits molecules and atoms, they will vibrate in specific, measurable ways -- a field of science known as spectroscopy. One of Cami's colleagues, who was studying Tc 1, found some unfamiliar fingerprints in the nebula's infrared light. Cami recognized them as carbon's 60-atom configuration and its favored 70-atom carbon partner.
"Cami's data is just so beautifully convincing. They have got some observations that there's almost nothing else interfering," Florida State University chemist Harold Kroto said in an interview.
In 1985, Kroto, with the University of Sussex in the United Kingdom at the time, and colleagues at Rice University in Texas were conducting laboratory experiments to try to understand how long chains of carbon molecules could be made. The carbon chains were found in interstellar space with radio telescopes in the 1970s.
They ended up discovering a third form of solid carbon, perfectly symmetrical geodesic spheres, which they named buckminsterfullerene after the American architect Buckminster Fuller. The most widely known fullerene is a buckyball -- 60 carbon atoms arranged by pentagons and hexagons into a hollow molecular cage one-billionth of a meter wide.
The discovery, which earned Kroto and colleagues Robert Curl and Richard Smalley the 1996 Nobel Prize in Chemistry, opened new frontiers in organic chemistry, physics, materials sciences and electronics.
The molecule proved a stable scaffold for creating new molecules that could hold and dispense electrical charges. Nanotechnology, the science of building materials one atom at a time, was born.
The finding of buckyballs in space may be similarly profound. Buckyballs, for example, may be responsible for mysterious sets of chemical fingerprints in the interstellar medium, known as the diffuse interstellar bands.
"Once you form fullerenes, it's hard to destroy them. They survive high energy, harsh radiation, even cosmic rays hitting them. They're very stable," Cami said. "This is actually just the beginning of a new research field."
The study is published in this week's issue of Science.