Webb finds largest amount of carbon ever seen in a planet-forming disk

The James Webb Space Telescope (JWST) continues to revolutionize our understanding of the cosmos, this time by uncovering a surprising abundance of carbon-rich molecules in the planet-forming disks around very low-mass stars. 

This remarkable discovery challenges our previous assumptions about the composition of these disks and raises intriguing questions about the nature of planets forming in such environments.

Planetary disks around young stars

Planets form within rotating disks composed of gas and dust, which surround young stars. 

The MIRI Mid-Infrared Disk Survey (MINDS) project, under the direction of Thomas Henning at the Max Planck Institute for Astronomy, utilizes the James Webb Space Telescope’s Mid-Infrared Instrument (MIRI) to investigate these protoplanetary disks with exceptional precision. 

By examining the chemical composition and physical characteristics of these disks, researchers seek to unravel the intricate processes that lead to planet formation and determine the potential types of planets that can emerge around stars with varying masses and properties. 

Abundance of carbon gases around star disks

In a recent study the MINDS team focused on a disk around a very low-mass star, just 11% the mass of our Sun. 

What they found was astonishing: the disk was teeming with carbon-bearing molecules like methane, ethane, ethylene, and even benzene, but lacked oxygen-rich compounds like water and carbon dioxide.

“This is profoundly different from the composition we see in disks around solar-type stars, where oxygen-bearing molecules such as water and carbon dioxide dominate,” explained Inga Kamp, a member of the research team from the University of Groningen.

“These molecules have already been detected in our solar system, like in comets such as 67P/Churyumov–Gerasimenko and C/2014 Q2 (Lovejoy),” added  lead author Aditya Arabhavi of the University of Groningen.

“Webb allowed us to understand that these hydrocarbon molecules are not just diverse but also abundant. It is amazing that we can now see the dance of these molecules in the planetary cradles. It is a very different planet-forming environment than we usually think of,” Arabhavi concluded.

Implications for planet formation

This unexpected finding suggests that disks around very low-mass stars evolve differently than those around more massive stars like our Sun. 

This difference in composition could have significant implications for the types of planets that form in these environments.

The abundance of carbon in these disks suggests that rocky planets forming around very low-mass stars might be carbon-rich, unlike Earth. 

Their atmospheres, if any, might be dominated by hydrocarbon compounds rather than oxygen and water vapor.

“Many primary atmospheres of those planets will probably be dominated by hydrocarbon compounds and not so much by oxygen-rich gases such as water and carbon dioxide,” said Thomas Henning.

Mystery of missing oxygen

While the carbon-rich nature of these disks is clear, the reason behind this imbalance remains a mystery. It could be due to an enrichment of carbon or a reduction of oxygen in the disk’s material. Further research is needed to unravel this puzzle.

If the carbon enrichment is caused by the vaporization of carbon from solid particles in the disk, then the resulting rocky planets would be carbon-poor, similar to Earth. However, their atmospheres would still be dominated by carbon-based chemistry.

Webb’s unique capabilities

The discovery of this carbon-rich chemistry was made possible by JWST’s unique capabilities. 

“It’s incredible that we can detect and quantify the amount of molecules that we know well on Earth, such as benzene, in an object that is more than 600 light-years away,” added team member Agnés Perrin of Centre National de la Recherche Scientifique in France.

Its high sensitivity and spectral resolution allowed the researchers to detect faint emissions from less abundant molecules that were previously undetectable.

“These observations are not possible from Earth because the relevant gas emissions are absorbed by its atmosphere,” said Arabhavi.

Planetary disks, carbon, and the search for life

This discovery marks a new era in our understanding of planet formation and carbon molecules within star disks. 

It challenges our preconceived notions and opens up a whole new realm of possibilities for the types of planets that might exist in the universe.

The MINDS team plans to expand their research to study a larger sample of disks around very low-mass stars. 

This will help them determine how common these carbon-rich environments are and shed light on the processes that lead to their formation.

“Expanding our study will also allow us to understand better how these molecules can form,” said Thomas Henning. “Several features in the data are also still unidentified, warranting additional spectroscopy to interpret our observations fully.”

The James Webb Space Telescope continues to push the boundaries of our knowledge, revealing the hidden secrets of the universe and expanding our understanding of our place in the cosmos. 

With each new discovery, we are reminded of the vastness and complexity of the universe and the endless possibilities that await us in our quest for knowledge.

The study is published in the journal Science.

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