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Spaceballs? Well, buckyballs at least

Erin Podolak

Researchers have discovered the presence of buckyballs in the nebula surrounding a distant white dwarf star, making the molecules the largest known to exist in space.

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Buckyballs have been found in space, according to researchers from the University of Western Ontario (Canada), SETI Institute (Mountain View, CA), Cornell University (Ithaca, NY) and the Institut d’Astrophysique Spatiale (Paris). The soccer ball–shaped carbon molecules were identified in the planetary nebula Tc-1, surrounding a white dwarf star. The finding establishes buckyball molecules C60 and C70 as the largest confirmed to exist in space.

Buckyballs belong to a class of molecules called fullerenes, named after architect Buckminster Fuller. In a laboratory setting, buckyballs are formed by vaporizing graphite in the presence of helium. The formation of buckyballs requires a carbon-rich and hydrogen-poor environment, because hydrogen inhibits the formation of buckyballs. Since this elemental makeup exists in space, buckyballs have long been thought to be present in the clouds of gas and dust between and around stars. But the molecules have remained elusive.

A rendering of buckyball molecules outside a planetary nebula. Source: NASA.

Now, the research team has found and identified fullerene molecules in space using an infrared spectrograph (IRS) onboard the Spitzer Space Telescope. Molecules in space absorb infrared light at unique wavelengths, which serve as chemical “fingerprints” that can be used in identification. The researchers knew they had found something when they didn’t recognize the fingerprint picked up by the Spitzer-IRS.

“We were not specifically looking for buckyballs,” Jan Cami, assistant professor of astronomy at the University of Western Ontario, told BioTechniques. “One of our collaborators on this work was using data generated by the Spitzer-IRS in the public archive to evaluate the chemical properties of planetary nebulas. He recognized a unique chemical fingerprint, but he wasn’t sure what it was.” Cami, who has previously worked with the Spitzer Space Telescope, and who also has knowledge of fullerenes, evaluated the data and confirmed that the molecules were buckyballs.

From the Spitzer-IRS data, the researchers identified C60 and C70 buckyball molecules (named for the number of carbon atoms each contains). The team’s finding is the only case where the presence of buckyballs—in pristine condition and free of other chemical or molecular contaminants—has been confirmed in space.

The discovery was made in the Tc-1 planetary nebula which is 6,500 light-years away from Earth in the southern constellation Ara. Despite the name, planetary nebulas are clouds of gas around stars, not planets. The Tc-1 planetary nebula surrounds a dense, dim, white dwarf star, and is the outer layer of what used to be a red giant star. The cloud that gathers around this star sheds layers through chemical reactions, and is ionized by radiation from the inner star, creating the planetary nebula.

Typically, this type of nebula would contain hydrogen that stops the chemical reaction that would produce fullerenes. However, the researchers believe the C60 and C70 buckyballs were able to form on grains of dust in the Tc-1 nebula due to an uncharacteristic high-carbon, low-hydrogen environment in the nebula. “We don’t know how the star got rid of its hydrogen millions of years ago,” said Cami. “We have also not yet looked into how common this low-hydrogen environment is in other nebulas.”

According to Cami, the data that led to the discovery of the buckyballs was actually generated by the Spitzer Space Telescope on March 21, 2005, and was made public for analysis one year later. The telescope records a significant amount of data that the researchers intend to continue sorting through, looking for further evidence of buckyballs and determining the conditions necessary for their formation.

“Buckyballs are complex molecules,” said Cami. “The structural arrangement of hydrocarbons in a soccer ball shape—and the very idea that these carbons naturally form this arrangement in space—shows that it is fairly easy to make complex molecules in space. This opens up a lot of questions about what other complex molecules could naturally form.”

The paper, “Detection of C60 and C70 in a young planetary nebula,” was published July 23 in Science.