The spectacular birthplace of weird carbon molecules known as “buckyballs” came to light in new imagery of a nebula from the James Webb Space Telescope. The gas cloud includes an upside-down question mark shape, which marks a structure scientists don’t yet understand.
The James Webb Space Telescope (JWST) peered 10,000 light-years into space to trace the origin of buckyballs, which are large and hollow molecules resembling a soccer ball. The gas cloud the observatory imaged, known as Tc1, came from a dying star, in the constellation Ara (Latin for “alter”) in the southern hemisphere.
Cami also led the team that first found cosmic buckyballs in 2010, a discovery notable enough to be published in the journal Science. That study was conducted using NASA’s Spitzer Space Telescope which, like JWST, observed in infrared wavelengths.
But Spitzer’s mission ended in 2020. JWST, which has a larger mirror and is further away from Earth, can now pick up where Spitzer left off and zoom in on the details.
Ingredients of life
Buckyballs are more properly known by their chemical name, buckminsterfullerene. This form of carbon is named after Buckminster Fuller, a space futurist and architect known for his work on hemispherical structures called geodesic domes. Buckyballs somewhat resemble the domes, which is how they got their name in a 1985 paper led by Harry Kroto at the University of Sussex. Some team members, including Kroto, later earned the 1996 Nobel Prize in Chemistry based on the paper. Decades later, however, the origin story of these carbon spheres remains enigmatic.
Buckyballs are significant as a type of polycyclic aromatic hydrocarbons (PAHs), which are a class of organic compounds — essentially, ingredients of life. Each of these PAHs has unique “signatures” or spectra of light, although they share properties because they are part of the same family, Cami said.
“We are now in a situation where we can actually see, especially within this object, how these buckyballs change as a function of changes in temperature, density and radiation field,” Cami told Space.com. The insights from this discovery could provide insights into how organic molecules form and evolve.
“We find them [buckyballs] in many more objects, of very different kinds,” Cami said. “It’s not just dying stars. We also find them in young stars. We see them in interstellar clouds. In star-forming regions. We’ve also found them in meteorites. So we see them essentially everywhere … but we don’t see them very frequently. And that’s a bit of the mystery.”
How the sun will die
The gas cloud JWST observed, known as Tc 1, includes a star similar in size to our own sun — but much older. The star has no more fuel to burn and has shed layers of gas and dust in a series of shells, blasting out into space. What’s left behind is a glowing core, known as a white dwarf, which is sending out radiation that causes the gas shells to glow.
It was near this star where Cami’s team first spotted buckyballs in 2010, and there were many reasons for a revisit. JWST not only has higher resolution allowing for much finer details in observations, but in the intervening years, few other such “planetary nebula” like Tc 1 (the moniker has to do with the shape of the gas, not with planets) have been found with buckyballs.
“In several hundred planetary nebulas, we found them in like a handful. Maybe 10 at most. And why in those 10 and not in the other ones, we still don’t know,” Cami said.
Scientists are planning a detailed look at Tc 1, as the analysis is just beginning, to figure out if buckyballs formed in this region similarly to how they do on Earth. (Cami said how terrestrial buckyballs form is a little obscure, although it tends to involve large amounts of carbon, low oxygen, and high temperatures.)
The team also wants to know why cosmic buckyballs are emitting infrared wavelengths in a way not predicted by models of how ultraviolet radiation is absorbed.
“None of our models actually correctly predicts what the correct emission would be, and that tells us that there’s something about these processes that we haven’t fully figured out. Maybe we’re missing some processes. Maybe our laboratory experiments for some of the parameters that we need, are not as accurate as we need them to be,” Cami said.
Box in a box
A first step is mapping where the buckyballs are located. Morgan Giese, a physics and astronomy PhD candidate at Western, discovered the buckyballs are mostly surrounding the white dwarf in their own shell. In a statement, Giese called the shape “buckyballs arranged like one giant buckyball”, and added why that is happening is a mystery.
Other details are coming soon from the JWST image, which was taken with the telescope’s mid-infrared instrument or MIRI. Saunders Secondary School science teacher K. Beecroft processed the image, Cami said; they met through school-outreach events at Western, and also connected through the university’s observatory program.
“She’s an amateur astronomer … I’ve been very impressed with her images, and so I asked her if she was interested in doing this. Within just a few hours, she sent me this image. I was like, ‘Holy cow.'”
Aside from tracing the filaments of gas, the telescope spotted spectroscopic details that will be released soon in a series of science papers. One of the papers will talk about that infrared-emission mystery, Cami said, with the details forthcoming once an embargo lifts.
“We’re actually looking at what the physical processes are that essentially cause the buckyballs to emit in infrared. We found that there’s a few more processes at play than we actually thought before,” he said.
More generally, the observations not only are showing the birthplace of buckyballs, but what happens to the environment as a dying star collapses: that would be the nebula’s temperature, chemical components, density and gas motions. Scientists are calling this the first-ever detailed view of a planetary nebula, and are hoping to bring their insights to similar nebulas elsewhere.
Cami’s team was awarded more time on JWST to look at two other planetary nebulas in the fall, which also have a lot of buckyballs visible in their spectrum. “What’s different in those objects is essentially that the radiation field is very different. So we picked those to see, to really study, what is the impact of the radiation field,” Cami said.
The team suggests that photochemistry and photophysics — chemistry and physics driven by light emissions — likely influences how those environments are shaped, but understanding just how will require more study.