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Webb Telescope Exposes New Clues in the Search for Alien Life

The disk surrounding a young red dwarf contains a surprising mix of chemicals that could inform the search for life in these common systems.
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Image: Getty Images

The world’s most powerful space telescope has captured an unprecedented glimpse of a young star system that contains clues about the existence of extraterrestrial life, reports a new study. The results shed light on the potential habitability of planets that form around red dwarf stars, which are much smaller and far more common than stars like the Sun.

Astronomers used the NASA-led James Webb Space Telescope (JWST) to peer at the swirling disk of gas and dust around a star called J160532, which is a red dwarf about 15 percent as massive as the Sun that is located 500 light years from Earth. J160532 is only a few million years old, making it a newborn in stellar terms—especially given that red dwarfs are expected to live for trillions of years.  

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Young star systems can serve as useful natural laboratories because they expose the raw ingredients that get baked into alien worlds, which have implications for their capacity to host life. The habitability of red dwarf systems is particularly interesting because many Earth-sized rocky exoplanets have been discovered orbiting these small stars, suggesting they may be promising candidates in the search for aliens. 

Now, scientists led by Benoît Tabone, an astrophysicist with the French National Centre for Scientific Research based at Paris-Saclay University, have discovered a weird mix of elements surrounding J160532, including an abundance of carbon and a scarcity of oxygen and water. The team also spotted benzene and diacetylene in the planet-forming zone surrounding J160532, marking the first time these organic molecules have ever been seen in this region of a star system.

The “much higher spectral resolution” of JWST, relative to previous telescopes, revealed these “important consequences for the composition of forming exoplanets,” according to a study published on Thursday in Nature Astronomy

“M dwarfs are the most common stars in the Galaxy and are known to host exoplanets in abundance,” Tabone and his colleagues said in the study. “However, the terrestrial planet-forming zones of the disks around M dwarfs have been largely inaccessible with previous observations due to limited spatial and spectral resolution and the dim nature of these objects.”

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“​​Our JWST data reveal that the chemistry in disks around such very low-mass stars may have an even higher gaseous carbon/oxygen ratio in the planet-forming zones than thought before,” the team added. “This, in turn, could significantly affect the composition of planets that may form around them.”

Tabone and his colleagues are part of a larger international collaboration known as the  Mid-Infrared Disk Survey (MINDS) that uses JWST’s sharp mid- infrared instrument (MIRI) to resolve fine details about the disks surrounding stars. While J160532 has previously been observed with NASA’s Spitzer space telescope, the new JWST images, captured in August 2022, offer the most detailed look at this fledgling star system yet.

The planet-forming disk surrounding the young red dwarf turned out to be rich in hydrocarbons, which are complex carbon molecules, and depleted in oxygen and water. Simple carbon compounds, such as carbon monoxide and carbon dioxide, are very common in young disks, but Tabone’s team are the first to see such an unusual hydrocarbon cocktail that included benzene and diacetylene.

“The most striking feature of the J160532 MIRI spectrum is the dominance of hydrocarbon emission” while “in contrast, at best weak [water] emission is found,” the team said. “Hydrocarbon molecules such as diacetylene and benzene have been found previously in some astrophysical environments, including asymptotic giant branch stars, comets and moons in our own Solar System, but not yet in the planet-forming zones of disks.” 

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“These detections therefore highlight that the inner disks around very low-mass objects are indeed very rich in carbon-bearing molecules as suggested on the basis of Spitzer data,” the researchers said.

The team speculated that disks around low-mass stars may become depleted in oxygen, and therefore water, because these essential ingredients for life get locked into ice grains that condense on pebbles and small rocks farther from the star. This scenario seems as if it would produce carbon-rich planets with almost no water, but that outcome isn’t assured because the dynamics of planet formation are complicated and filled with unknowns.

For instance, Tabone and his colleagues suggest that “carbon-rich gas could be lost from the system over time, with only a small fraction of carbon eventually included in planets,” according to the study. Meanwhile, planets that are initially devoid of water and oxygen may obtain these important substances from icy bodies, such as asteroids and comets, that collide with them later in the evolution of a star system. 

In other words, the new study has collected a few more pieces of the planetary puzzle, but it will take more research to understand how new worlds are forged around these small stars, and whether they might one day support extraterrestrial life. To that end, Tabone and his colleagues hope to examine more observations of young systems like J160532, while also looking at the planets that have formed around their older counterparts.

“These two competing scenarios—making carbon-rich versus carbon-poor terrestrial planets—can be tested by comparing high sensitivity JWST observations of the chemical composition of significant samples of disks around very low-mass young stars with that of the atmospheres of terrestrial-sized planets around mature brown dwarfs and M stars such as the Trappist I system,” the team said in the study.

“Carbon is an essential element for life but how much can be delivered to young planets is still an open question,” the researchers concluded. “The chemical characterization of planet-forming disks is a crucial step in our understanding of the diversity and habitability of exoplanets.”