This is an artist’s impression of a young star surrounded by a disk of gas and dust. An international team of astronomers used NASA’s James Webb Space Telescope to study the disk around a young, very low-mass star known as ISO-ChaI 147. The results reveal the richest hydrocarbon chemistry yet observed in a protoplanetary disk. Credit: NASA/JPL-Caltech
The habits James Webb Space TelescopeScientists have discovered a rich variety of carbon molecules in a protoplanetary disk around a low-mass star, indicating a unique kind of planet-forming environment that could lead to the creation of low-carbon planets.
An international team of astronomers has studied the disk of gas and dust surrounding a young, very low-mass star NASA‘s James Webb Space Telescope (JWST). The results reveal the largest number of carbon-containing molecules observed in such a disk to date. These findings have implications for the potential composition of any planets that could form around this star.
Implications for planet formation
Rocky planets are more likely to form around low-mass stars than gas giants, making them the most common planets around the most common stars in our Milky Way. Little is known about the chemistry of such worlds, which may be similar or very different from Earth. By studying the disks from which such planets form, astronomers hope to better understand the planet formation process and the compositions of the resulting planets.
Planet-forming disks around very low-mass stars are difficult to study because they are smaller and fainter than disks around high-mass stars. A program called MIRI (Mid-Infrared Instrument) Mid-INfrared Disk Survey (MINDS) aims to use Webb’s unique capabilities to bridge the gap between the chemical inventory of disks and the properties of exoplanets.
“Webb has better sensitivity and spectral resolution than previous infrared space telescopes,” explains lead author Aditya Arabhavi from the University of Groningen. “These observations are not possible from Earth because the emissions from the disk are blocked by our atmosphere.”
The spectrum of the star ISO-ChaI 147, revealed by MIRI (Mid-Infrared Instrument) on NASA’s James Webb Space Telescope, shows the richest hydrocarbon chemistry yet observed in a protoplanetary disk, consisting of 13 carbonaceous molecules. This includes the first extrasolar detection of ethane (C2H6). The team also successfully detected ethylene (C2H4), propyne (C3H4) and the methyl radical CH3 in a protoplanetary disk for the first time. Credit: NASA, ESA, CSA, R. Crawford (STScI)
Groundbreaking discoveries in exoplanetary chemistry
In a new study, this team explored the region around a very low-mass star known as ISO-ChaI 147, a 1- to 2-million-year-old star that weighs only 0.11 times as much as the Sun. The spectrum revealed by Webb’s MIRI shows the richest hydrocarbon chemistry yet observed in a protoplanetary disk: a total of 13 different carbonaceous molecules. The team’s findings include the first detection of ethane (C2H6) outside our solar system, as well as ethylene (C2H4), propyne (C3H4), and the methyl radical CH3.
“These molecules have already been detected in our solar system, such as in comets such as 67P/Churyumov-Gerasimenko and C/2014 Q2 (Lovejoy),” Arabhavi said. “Webb helped us understand that these hydrocarbon molecules are not only diverse but also abundant. It’s amazing that we can now see the dance of these molecules in the planetary cradles. It’s a very different planet-forming environment than we usually think.”
The team indicates that these results have major implications for the chemistry of the inner disk and the planets that could form there. Because Webb revealed that the gas in the disk is so rich in carbon, there is likely little carbon left in the solid materials from which planets would form. As a result, the planets that could form there could end up being low-carbon. (The Earth itself is considered low-carbon.)
“This differs greatly from the composition we see in disks around solar-type stars, where oxygen-containing molecules such as water and carbon dioxide dominate,” says team member Inga Kamp, also from the University of Groningen. “This object confirms that this is a unique class of objects.”
“It is incredible that we can detect and quantify the amount of molecules we know well on Earth, such as benzene, in an object more than 600 light-years away,” said team member Agnés Perrin of the Center National de la Recherche Scientifique. In France.
Future research directions
Next, the science team plans to expand their research to a larger sample of such disks around very low-mass stars, to gain insight into how common or exotic such carbon-rich planet-forming regions are on Earth. “The expansion of our research will also allow us to better understand how these molecules can form,” explains team member and principal investigator of the MINDS program, Thomas Henning, from the Max Planck Institute for Astronomy in Germany. “Several features in the Webb data also remain unidentified, so more spectroscopy is needed to fully interpret our observations.”
This work also highlights the critical need for scientists to collaborate across disciplines. The team notes that these results and associated data could contribute to other fields, including theoretical physics, chemistry and astrochemistry, to interpret the spectra and explore new features in this wavelength range.
For more information about this discovery, see Webb Unmasks the Carbon-Rich Secrets of Protoplanetary Disks.
Reference: “Abundant hydrocarbons in the disk around a very low mass star” by AM Arabhavi, I. Kamp, Th. Henning, E.F. van Dishoeck, V. Christiaens, D. Gasman, A. Perrin, M. Güdel, B. Tabone, J. Kanwar, LBFM Waters, I. Pascucci, M. Samland, G. Perotti, G. Bettoni, SL Grant, PO Lagage, TP Ray, B. Vandenbussche, O. Absil, I. Argyriou, D. Barrado, A. Boccaletti, J. Bouwman, A. Caratti o Garatti, AM Glauser, F. Lahuis, M. Mueller, G Olofsson, E. Pantin, S. Scheithauer, M. Morales-Calderón, R. Franceschi, H. Jang, N. Pawellek, D. Rodgers-Lee, J. Schreiber, K. Schwarz, M. Temmink, M. Vlasblom. , G. Wright, L. Colina and G. Östlin, June 6, 2024, Science.
DOI: 10.1126/science.adi8147
The James Webb Space Telescope is the world’s premier observatory for space science. Webb solves mysteries in our solar system, looks beyond to distant worlds around other stars and investigates the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA and its partners ESA (European Space Agency) and CSA (Canadian Space Agency).