Buckyballs Discovered in Another Galaxy

27 October 2010

Astronomers using NASA’s Spitzer Space Telescope have detected arrangements of carbon atoms known as buckyballs outside of the Milky Way galaxy for the first time. Sir Harry Kroto of Florida State University, who won a Nobel Prize for discovering buckyballs, says life may even owe its existence to the atom “cages” which resemble soccer balls. The discovery of buckyballs in the Small Magellanic Cloud suggests that these complex molecules may be present around many stars where it was predicted they would be unlikely to form. Extensive follow-up studies using ground-based telescopes will be used to establish the conditions helpful for the formation of buckyballs in our galaxy and other galaxies.

Astronomers using NASA’s Spitzer Space Telescope have detected arrangements of carbon atoms known as buckyballs outside of the Milky Way galaxy for the first time. Sir Harry Kroto of Florida State University, who won a Nobel Prize for discovering buckyballs, says life may even owe its existence to the atom “cages” which resemble soccer balls. The discovery of buckyballs in the Small Magellanic Cloud suggests that these complex molecules may be present around many stars where it was predicted they would be unlikely to form. Extensive follow-up studies using ground-based telescopes will be used to establish the conditions helpful for the formation of buckyballs in our galaxy and other galaxies.

Letizia Stanghellini of the National Optical Astronomy Observatory in Tucson, Arizona, and her team from Europe used Spitzer telescope data to find the characteristic infrared signature of spherical fullerenes called buckyballs in four planetary nebulae. The fullerenes are created in the shells of gas and dust ejected from the dying stars at the center of these often-photogenic nebulae.

“Life on Earth has a love affair with carbon, because carbon chemistry is the chemistry of life,” Stanghellini explains. “Our discovery shows that these carbon buckyballs, which have also been found in meteorites and around stars in our own galaxy, are probably quite common in all galaxies.”

“These complicated molecules were once thought to be very rare, while now they are found in the rather common objects that planetary nebulae are,” said NOAO team member Richard Shaw. “It is clear that there is a lot of fullerene out there.”

Around one star observed by the Stanghellini team, the total mass of C₆₀, a common type of fullerene, is more than 3 times the mass of the planet Mercury. These carbon compounds are dispersed around the star and may form on small grains of dust in the material ejected from the star.

Using the Spitzer Infrared Spectrometer instrument, the team searched in dozens of planetary nebulae that were known to have hydrogen-rich shells of gas that had been ejected from the dying star. This ejected material contains carbon grains (much like soot) that had condensed farther from the star. In this cooling process, and under the exposure to ultraviolet radiation, the grains not only can form fullerenes but other carbon molecules called polycyclic aromatic hydrocarbons (PAHs) – which can be created on Earth in the exhaust of diesel engines.

“The four fullerene-rich planetary nebulae detected by us are within reach of the NOAO telescopes for follow-up spectroscopy,” said Shaw, “as well as the large sample of planetary nebulae we searched for fullerene. We are planning a scrupulous follow-up to determine the temperatures and composition of their hot gas flows, with the aim of determining the physical and evolutionary characteristics of the fullerene-rich objects compared to the general planetary nebula population.”

Previous work had identified dying stars called planetary nebula as possible sources of fullerenes. However it was expected that only stars with gas surrounding them that was depleted in hydrogen would be able to form fullerenes.

“We have been studying all kinds of planetary nebula from the ground and from space for 15 years, examining more than 250 nebulae in the Milky Way and beyond, in search for common trends and special features. Our Spitzer observations were designed to have the sensitivity to detect both gas and dust features, including carbon molecules such as fullerene”, says Stanghellini.

“The prevailing view has been that fullerenes cannot occur in hydrogen-rich outflows from these stars. On the contrary, we have found that these fullerenes may be fairly common in these kinds of hydrogen-rich environments” added team member Pedro García-Lario of the European Space Astronomy Centre in Spain.

Buckyballs and related fullerenes such as nanotubes are certainly one of the more interesting and elegant patterns of carbon atoms, and have very different properties than diamond, where carbon bonds in all directions, or graphite, where it occurs in sheets and flakes off easily. In the chemistry lab, scientists are hard at work making super strong carbon nanotubes and in trying to insert atoms or even drugs inside the carbon balls. The creative possibilities of how these molecules can be used are extensive but largely undeveloped. The little ball-shaped molecules can be made into threadlike tubes that are visible to the eye, and extremely strong. Scientists are investigating whether these tubes can be made into very thin body armor that could stop any bullet or even be used in a “space elevator” cable to haul materials to and from geosynchronous orbit.

Scientists can verify the existence of fullerenes by looking at how they emit infrared light – each molecule has a unique fingerprint. The infrared signature was used by the astronomers to distinguish fullerenes from other carbon compounds, such as PAHs.

The team has concluded that significant chemical reprocessing of the carbon has occurred, indicating that more complex carbon chemistry might be also occurring. This means that the fullerenes could be altered in even more unusual ways.

Although the molecules were detected using a space-based infrared telescope, many new studies of their cosmochemistry are being done with laboratory chambers simulating the stellar and interstellar environment and with ground-based telescopes that can yield clues on the nature of stellar ejecta.

According to team member Arturo Manchado, “We hope this discovery stimulates the cosmochemists to understand better the large number of ways that these compounds can be made. Most of the luminous mass in the Universe is in low-mass stars, and almost all of these stars go through the planetary nebula phase. Our results indicate that fullerenes can form under conditions which are common to essentially all Solar-like stars at the end of their lives.”

The measurements made with the Spitzer Space Telescope could only have been made from space because the infrared sky is too bright from the ground, and much of the infrared radiation emitted by these fullerenes is absorbed by the Earth’s atmosphere.

The members of the team are Anibal García-Hernández and Arturo Manchado of the Instituto de Astrofísica de Canarias (Spain), Pedro García-Lario of the European Space Agency Centre (Madrid, Spain), Letizia Stanghellini and Richard Shaw of the National Optical Astronomy Observatory (Tucson, Arizona), Eva Villaver of the Universidad Autónoma de Madrid (Madrid, Spain), Ryszard Szczerba of the Nicolaus Copernicus Astronomical Center (Toruń, Poland), and José V. Perea-Calderon of the European Space Astronomy Centre, Ingeniería y Servicios Aerospaciales, in Spain.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA.

More information

NOAO is operated by AURA under a cooperative agreement with the National Science Foundation.

Contacts

Dr. Letizia Stanghellini
National Optical Astronomy Observatory
950 N. Cherry Ave. Tucson, AZ 85719, USA
Tel: (520) 318-8205
Cell: (520) 465-3052
Email: letizia@noao.edu