Buckyballs — those intriguing molecular spheres made up entirely of carbon — are found in space near the dying stars, but no one knew the reason why. Now, new research from the Lunar and Planetary Lab in Tucson reveals how these complex structures form in space.
Buckyballs are spherical molecules, consisting entirely of 60 carbon atoms, arranged in a pattern of pentagrams or hexagrams meeting at their edges, like a soccer ball. Known as carbon 60 (or C6O), they were first seen in the laboratory, and were thought to be solely an artificial construct.
However, several years ago, astronomers detected these behemoth molecules in the space between stars. However, no one was able to explain why — or how — buckyballs would form in space.
Now, new research from the Lunar and Planetary Lab in Tucson, Arizona shows a means by which dying stars could produce these molecular structures.
Having a Ball with Carbon
Buckminsterfullerene, or buckyballs, are named in honor of famed architect Buckminster Fuller, best known for his design of domed-shaped buildings.
Much like graphene, these structures are composed solely of a single layer of carbon atoms, but the atoms in graphene form into a flat sheet, while buckyballs take the shape of a sphere.
Until recently, astronomers believed that interstellar space was filled with just single atoms or small molecules. When the presence of C60 in space was first recorded, the discovery marked a significant change in our understanding of the regions between the stars.
“Life on Earth has a love affair with carbon, because carbon chemistry is the chemistry of life… these carbon buckyballs, which have also been found in meteorites and around stars in our own galaxy, are probably quite common in all galaxies,” Letizia Stanghellini of the National Optical Astronomy Observatory (now NSF’s National Optical-Infrared Research Laboratory) stated in 2010.
In addition to C60, researchers discovered buckyballs made of 70 carbon atoms. Even in the depths of space, these structures were composed entirely of carbon, like the molecules produced in laboratories.
These molecules were found in planetary nebulae — the gaseous clouds ejected from a dying star. These clouds hold on to 10,000 molecules of hydrogen for every carbon molecule, adding mystery to the production of the buckyballs.
“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,” said Jacob Bernal, a astrobiology and chemistry doctoral student and lead author of a paper describing the study.
In addition to sheer numbers, hydrogen should have hindered the development of the massive molecules. The mystery of how these molecules formed under natural environments drew the attention of researchers.
“Carbon 60 is a very large molecule for interstellar chemistry, and it consists purely of carbon atoms. It is very puzzling why such a molecule would form in a very hydrogen-rich environment of interstellar space, where the number of H atoms is [around] 10,000 times the number of carbon atoms. More likely, carbon would bond to hydrogen, so why C60? It’s a great chemical question, and it attracted our interest,” Lucy Ziurys, Regents Professor of astronomy, chemistry and biochemistry at the University of Arizona tells The Cosmic Companion.
Using a Microscope to Study Space?
The study was born when Bernal and his team realized the transmission electron microscope (TEM) housed at the Kuiper Materials Imaging and Characterization Facility at the University of Arizona, could closely simulate the conditions found in planetary nebulae.
Operating at extremely low pressures, the instrument is able to eliminate distortions caused by air, allowing TEM to explore matter down to 78 picometers, around 100,000 times thinner than a human hair. This extreme vacuum inside this instrument made it the perfect vessel to use in exploring how C60 could form within the tenuous gas of planetary nebulae.
The team partnered with the Argonne National Lab near Chicago, where another TEM, with the added ability to measure radiation responses of samples, was available for use.
Researchers placed silicon carbide (a dust common in planetary nebula) inside the machine, heated the material to a temperature of 1,000 degrees Celsius (1,830 F), and bombarded it with high energy ions of xenon.
The samples were returned to the LPL in Tucson, where they was analyzed using the TEM at that facility (which provided superior resolution to the Chicago-based instrument). Researchers found evidence that silicon shed during the exposure, exposing pure carbon, showing that C60 could be produced in space through natural processes.
“Sure enough, the silicon came off, and you were left with layers of carbon in six-membered ring sets called graphite. And then when the grains had an uneven surface, five-membered and six-membered rings formed and made spherical structures matching the diameter of C60. So, we think we’re seeing C60,” Ziurys said.
Carbon Just Needs a Little Space
“We are nothing but space dust, trying to find its way back to the stars.”
― David Jones, Love and Space Dust
In the depths of space, dying stars release silicon carbide dust into space. There, the molecules experience high temperatures, impacts by energetic particles, and shockwaves passing through the thin clouds of dust and gas. These conditions peel silicon off the dust, exposing pure carbon which can form into buckyballs and complex structures.
“Other carbon nanostructures, such as nanotubes and other fullerenes, [can form] including endometallofullerenes, or EMFs. There are fullerenes with a metal inside the spherical structure,” Ziurys describes.
The team also identified a grain of silicon carbide surrounded by graphene in the Murchison meteorite, adding evidence to their theory for the formation of C60 in the expanses between the stars.
Future observations of buckyballs in space, looking at wavelengths from infrared to radio, could examine the locations of these products as well as silicon carbide. If the sources and locations of these are usually the same, it would lend evidence to help support the new study, according to Ziurys.
This study, published in The Astrophysical Journal, provides a new way of looking at some of the great questions of astrobiology, including the search for life on other worlds. New studies suggest that even life on Earth may have started in the clouds floating between stars.
“The forms carbon takes on in space also has important implications for astrobiology and ultimately the origin of life,” explained Ziurys.
The same harsh conditions thought to hinder the development of buckyballs in space turns out to be the very processes driving their formation.
Did you like this article? Subscribe to The Cosmic Companion Newsletter!