Fullerenes ("buckyballs") & PAHs

Fullerenes are a class of carbonaceous molecules in the shape of a hollow cage (see insets in the above image for a representation). The most famous of the fullerenes is the so-called "buckminsterfullerene" C60, shaped like a soccer ball. These molecules are therefore often referred to as buckyballs. They were discovered on Earth in 1985 by a team led by the late Sir Harry Kroto, and were immediately suggested to be widespread and abundant in space.

In 2010, I led a team that recognized the characteristic spectral fingerprints of C60 (indicated in red in the figure above) and C70 (in blue) in the infrared spectrum of a planetary nebula observed with the Spitzer Space Telescope. You can download our 2010 discovery paper in Science Detection of C60 and C70 in a Young Planetary Nebula by visiting Scholarship@Western and clicking the "full text reprint" link about halfway down the page). If you are interested, you can also read about the background of this discovery, as well as some more context and progress in the field in this Nature Astronomy interview.

Our discovery started the interdisciplinary field of fullerene space research that turned out to be an active and competitive field. Our aim is to understand how these fullerenes form and evolve in space, how they interact with their environment and how they in turn change their surroundings. This requires a large amount of observational data analysis as well as theoretical research, and requires a combination of physics, astronomy, chemistry and computer science.

Fullerenes are the only large carbonaceous species that we have been able to identify in space. However, we do know that about 15% of the carbon in the Universe is in the form of other molecules known as polycyclic aromatic hydrocarbons (PAHs) -- their infrared features shine brightly across the Universe! PAHs have properties that are very similar to those of fullerenes, and together with fullerenes, they play crucial roles in large-scale processes such as star and planet formation, and galaxy evolution. However, the spectral features of different PAHs coincide, and thus we cannot really track what is happening to individual PAH species in different environments. This has greatly hampered our progress in understanding the detailed molecular physics processes that are at play with these large carbonaceous molecules. Fullerenes on the other hand do not suffer from this effect, and they are thus the only species right now that allow us to study in general what happens to large organic species in space!

Current projects on cosmic fullerenes in my group include detailed investigations of C60-rich objects using optical (X-Shooter, UVES and soon also MUSE on the VLT) and infrared (Gemini, Spitzer Space Telescope, FIFI-LS and HAWC+ on SOFIA; and soon also the James Webb Space Telescope) observations. We are also developing a model that includes all the relevant molecular physics to predict the state and spectra of fullerenes in different environments.