Researchers from the Instituto de Astrofísica de Canarias (IAC) have found evidence that lin the presence of “carbon onions”and other large molecules derived fromfullerenos(a stable, spherical form of carbon) could bewidespread in space. These are the most complex molecules observed so far, and their finding has important implications for understanding circumstellar and interstellar physico-chemistry, as well as molecular processes in the later stages of the evolution of stars.
The study, which combines astronomical observations and theoretical physics, has found these complex molecules in the environment of two planetary nebulae rich in the most common fullerene (C60), suggesting that their presence may be more abundant than previously thought. “Planetary nebulae -low-mass stars in the final stage of their lives- produce organic molecules that are subsequently expelled into space, so they are essential to understand the molecular processes of the interstellar medium in which stars and planets form and to understand the processes of formation of precursor molecules of life “, explains Aníbal García-Hernández, main author of the article, which publishes the journalAstronomy and Astrophysics Letters.
Scientists had speculated in the past with the idea thatfullerenes, which can act as cages for other molecules and atoms, could have carried substances to Earth that would have fueled the beginning of life. Evidence for this theory comes from the fact that C60 fullerenes have been found in meteorites carrying extraterrestrial gases. However, “all this is speculation”, clarifies García-Hernández.
Interstellar diffuse bands
The work also provides new keys to understand the origin and composition of diffuse interstellar bands (DIBs), one of the most enigmatic phenomena in astrophysics. Scattered throughout space, the molecules responsible for these bands trap part of the visible light emitted by the stars, which reaches us dimmed. Discovered 90 years ago,interstellar diffuse bands are present in all directions of space (more than 400 are known), are more intense in areas with abundant interstellar dust and are characterized by trapping part of the visible light emitted by the stars. In fact, we know that they exist because, when observing the visible light spectrum emitted by a star, it is detected that certain wavelengths reach us damped. The researchers then deduce that something stands between the star and us: diffuse bands, so called because they generate characteristic absorption bands in the star’s spectrographs (something like its fingerprint). By studying the optical spectrum of the two planetary nebulae, the researchers found that two of the known DIBs were especially intense and that a new, previously unknown band appeared. “Fullerenes in their various manifestations (carbon onions, clusters of fullerenes, or even complex species formed by fullerenes and other molecules such as hydrocarbons or atoms) could hold the key to solving the mystery of DIBs,” suggests García-Hernández.
“The next step is to characterize all the DIBs of these planetary nebulae, as well as synthesize and characterize new molecules based on fullerenes and compare them with the astronomical data,” adds Jairo Díaz-Luis, co-signer of the study. “Unraveling the secret of the DIBs would allow us to understand what the interstellar medium is made of in all corners of the Universe”, he concludes.
