Scientists have long been perplexed by the presence of “buckyballs” — complex carbon molecules with a soccer-ball-like shape – in interstellar space. In a paper published in the Astrophysical Journal Letters, a team of researchers from the University of Arizona hypothesized a mechanism for their creation.
Carbon 60, or C60 for short, is a spherical molecule composed of 60 carbon atoms arranged in five-membered and six-membered rings. Its formal name is Buckminsterfullerene. The term “buckyball” refers to its resemblance to the architectural work of Richard Buckminster Fuller, who created numerous dome structures that resemble C60. Their creation was considered to be solely feasible in lab settings until they were discovered in space, which called this notion into question.
For decades, people assumed that interstellar space was primarily made up of lightweight molecules: single atoms, two-atom molecules, and the rare nine or ten-atom molecule. This was true until the discovery of large C60 and C70 molecules a few years ago.
Researchers were also surprised to discover that they were made entirely of carbon. C60 is created in the lab by blasting together pure carbon sources such as graphite. C60 was discovered in planetary nebulae, which are the remnants of dead stars, in space. There are approximately 10,000 hydrogen molecules for every carbon molecule in this atmosphere.
“Any hydrogen should destroy fullerene synthesis,” said astrobiology and chemistry doctoral student Jacob Bernal, lead author of the paper. “If you have a box of balls, and for every 10,000 hydrogen balls you have one carbon, and you keep shaking them, how likely is it that you get 60 carbons to stick together? It’s very unlikely.”
Bernal and his co-authors began looking into the C60 process after discovering that the transmission electron microscope, or TEM, located at UArizona’s Kuiper Materials Imaging and Characterization Facility could pretty effectively replicate the planetary nebula environment.
“The conditions in the universe where we would expect complex things to be destroyed are actually the conditions that create them,” Bernal said, adding that the implications of the findings are endless.
“If this mechanism is forming C60, it’s probably forming all kinds of carbon nanostructures,” Ziurys said. “And if you read the chemical literature, these are all thought to be synthetic materials only made in the lab, and yet, interstellar space seems to be making them naturally.”
If the findings are any indication, the cosmos may have more to teach us about how chemistry actually works.
Formation of Interstellar C60 from Silicon Carbide Circumstellar Grains, J. J. Bernal et al
Published: October 2019