A bizarre planet-forming disk is full of carbon dioxide in the regions where Earth-like planets could form, fresh observations from the James Webb Space Telescope (JWST) show.
Usually, such planet-forming disks contain water, but “water is so scarce in this system that it’s barely detectable — a dramatic contrast to what we typically observe,” Jenny Frediani, a doctoral student in the Department of Astronomy at Stockholm University and lead author of the research, said in a statement.
The findings, published Aug. 29 in the journal Astronomy & Astrophysics, challenge current ideas about planetary formation.
The science team still isn’t sure what’s going on at the star in NGC 6357, which is located 8,000 light-years from Earth, Frediani told Live Science in an email. However, further investigation into this system could help us understand more about the formation of Earth-like planets.
“These are the most common environments for the formation of stars and planets, and they also likely resemble the environment in which our own solar system formed,” Frediani told Live Science.
Oddball star
Typically, newborn stars are swaddled in gas clouds. They create disks of material from which planets and other objects, like comets or asteroids, may eventually form.
Previous models have suggested that, as these disks evolve, bits of rocky material rich in water ice move from the outer and colder edges of the planet-forming disk to the warmer center. As the pebbles move in toward the young stars, temperatures on the surface of the rocks rise and make the ices sublimate. JWST can then spot this sublimation through the signature of water vapor.
But when JWST examined this star, known as XUE 10, it spotted a surprise: the signature of carbon dioxide.
There are two theories that could explain the weird environment, Frediani explained.
One possibility is a strong source of ultraviolet (UV) radiation from the newborn star or from some massive nearby stars. “Both can emit enough UV radiation to significantly deplete the water reservoir in a disk early on,” she said.
Another reason may be due to dust grains in the region. Instead of having a lot of water coating the grains, perhaps the dust is replete with carbon dioxide “due to particular local environmental conditions around the young star,” she said.
If this were the case, water vapor would accrete on to the star, but “a relatively large amount of CO2 [carbon dioxide] vapor will remain visible in the disk before it is eventually accreted as well,” Frediani explained.
JWST is located at a gravitationally stable spot in space known as a Lagrange point, where it is far from interfering light from Earth or other celestial bodies. That remote location, paired with JWST’s powerful mirrors, makes the telescope the only one sensitive enough to capture details about how planet-forming disks form in distant and massive star-forming regions, Frediani said.
Frediani is part of the eXtreme Ultraviolet Environments collaboration, which examines how intense radiation fields affect the chemistry of disks around planet-forming stars. For now, JWST remains the consortium’s best bet for follow-ups of this strange system, but some upcoming ground observatories and upgrades will help, Frediani said.
For example, the long-running European Southern Observatory-led Atacama Large Millimeter/submillimeter Array in the Chilean desert is being upgraded, with hopes to have the changes operational by the 2030s.
The Wideband Sensitivity Upgrade, as the work is termed, will “allow us to image the cold gas and dust reservoirs in the outer regions of disks, located in distant star-forming regions,” Frediani said. This upgrade should allow researchers to see the root causes of phenomena such as disk truncation (or shrinking) happening due to strong external irradiation.
Another complementary ground observatory will be the Extremely Large Telescope (ELT), a 130-foot (39 meters) ESO observatory that’s under construction in Chile. When it’s completed around 2027, the ELT will be the largest of the next-generation ground-based optical and near-infrared telescopes, according to the ESO.
“The ELT will be powerful enough to resolve the fine structure of these irradiated disks, revealing, for example, substructures that may be linked to forming planets in the disk,” Frediani said.
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