Possibly catching a glimpse of a rare moment in space and time, researchers using NASA's Spitzer Space Telescope's Infrared Spectrograph (IRS) have detected fullerenes, or buckyballs -- carbon structures long thought to be likely features of the interstellar medium, but never before observed.
The finding, reported recently online in the journal Science by a team led by Jan Cami of the University of Western Ohio, could explain some puzzling chemical signatures, known as diffuse interstellar bands, that have been observed by various researchers in the interstellar medium since 1922. It also raises the potential for the existence of other, unseen elements or chemical reactions in the region.
Jeronimo Bernard-Salas, formerly a research associate working on Cornell's Spitzer team now at the Institut d'Astrophysique Spatiale in Orsay, France, was the first to notice the unusual features that were later identified as fullerenes in a young planetary nebula called Tc1. (A planetary nebula is one of the last phases of evolution of a star like the sun.)
"Tc1 was putting [on] quite a show," Bernard-Salas said. "These were not faint features, these were features that were dominating the whole spectrum."
Fullerenes (C60 and C70), also called buckminsterfullerenes or buckyballs, are the third form of carbon after graphite and diamond. Discovered in 1985 and named for geodesic dome designer Buckminster Fuller, they are spherical and highly stable, making them well-suited to survive the harsh conditions of the interstellar medium. Previous efforts to find them, though, have been unsuccessful.
Still, their presence in Tc1 is a surprise. During their last phases of evolution, stars experience mass ejection events in which they release large amounts of hydrogen. But while fullerenes can exist in hydrogen-rich environments, they can only form in hydrogen-poor ones -- leaving the question of why Tc1 was lacking in hydrogen at the time of their formation.
"It could be that we have caught this planetary nebula at a very specific time in terms of conditions," Bernard-Salas said. "In a few hundred years from now -- a short time in astrophysical scales -- the fullerenes could cool down enough to be no longer visible in the infrared."
So while the discovery is a milestone, it raises as many new questions as it answers, he added. "The ball game has just started."
The Spitzer telescope is the last of NASA's Great Observatories. The IRS, one of three science instruments on the observatory, is managed by NASA's Jet Propulsion Laboratory and was built by Ball Aerospace & Technologies Corp. under the direction of James Houck, Cornell's Kenneth A. Wallace Professor of Astronomy.