31.08.2025
James Webb Space Telescope spots odd planet-forming disk around infant star
'This challenges current models of disk chemistry and evolution'
Main: An illustration of a protoplanetary disk around an infant star. Inset: image of the star-forming region NGC 6357 with the young star XUE 10 as seen by the JWST. (Image credit: (Main) ESO/L. Calçada (Inset) Stockholm University (SU) and María Claudia Ramírez-Tannus, Max Planck Institute for Astronomy (MPIA).)
Using the James Webb Space Telescope (JWST), astronomers have discovered a strange disk of gas and dust around an infant star that could challenge current models of planet formation.
The protoplanetary disk has an odd chemical composition. It features a surprisingly high concentration of carbon dioxide in the region in which rocky planets like Earth are expected to form and is also unexpectedly low in water content.
The protoplanetary disk investigated by JWST surrounds the infant star XUE 10, which is located around 5,550 light-years from Earth in the vast star-forming region known as NGC 6357. The new discovery was made by the eXtreme Ultraviolet Environments (XUE) collaboration, a research team that focuses on how intense fields of radiation impact the chemistry of protoplanetary disks.
"Unlike most nearby planet-forming disks, where water vapor dominates the inner regions, this disk is surprisingly rich in carbon dioxide," XUE collaboration team member Jenny Frediani, of Stockholm University in Sweden, said in a statement.
"In fact, water is so scarce in this system that it’s barely detectable — a dramatic contrast to what we typically observe," Frediani added. "This challenges current models of disk chemistry and evolution, since the high carbon dioxide levels relative to water cannot be easily explained by standard disk evolution processes."
Strange chemistry
Stars form when overdense patches clump together in vast clouds of gas and dust, eventually gathering enough mass to undergo gravitational collapse. What remains of the material that birthed this still-growing protostar swirls around it, flattening out and eventually forming a protoplanetary disk in which planets can be born.
Scientists currently theorize that planet formation occurs when "pebbles" rich in water ice drift from the colder outer regions of a protoplanetary disk to its warmer inner regions. These higher temperatures cause solid ice to transform directly into gas, a process known as sublimation.
This usually also results in telescopes like JWST spotting strong signals from water vapor in protoplanetary disks. The disk around XUE 10, however, showed strong carbon dioxide signals.
"Such a high abundance of carbon dioxide in the planet-forming zone is unexpected," said XUE Collaboration member and Stockholm University researcher Arjan Bik. "It points to the possibility that intense ultraviolet radiation— either from the host star or neighboring massive stars — is reshaping the chemistry of the disk."
The star-forming region NGC 6357, with the position of the young star XUE 10 indicated (Image credit: Stockholm University (SU) and María Claudia Ramírez-Tannus, Max Planck Institute for Astronomy (MPIA).)
This wasn't the only surprise that JWST delivered to the team with regard to XUE 10 and its protoplanetary disk. Data from the disk revealed molecules of carbon dioxide, enriched with the carbon isotopes carbon-13 and the oxygen isotopes oxygen-17 and oxygen-18.
The presence of these isotopes could help explain why certain unusual isotopes are left in fragments of the early solar system in the formation of meteorites andcomets.
The research demonstrates JWST's impressive ability to detect chemical fingerprints in distant protoplanetary disks during crucial eras of planet formation.
"It reveals how extreme radiation environments — common in massive star-forming regions — can alter thebuilding blocks of planets," said team leader Maria-Claudia Ramirez-Tannus from the Max Planck Institute for Astronomy in Germany. "Since most stars and likely most planets form in such regions, understanding these effects is essential for grasping the diversity of planetary atmospheres and their habitability potential."
The team's research was published on Friday (Aug. 29) in the journal Astronomy & Astrophysics.
Quelle: SC
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Update: 10.09.2025
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NASA Webb Looks at Earth-Sized, Habitable-Zone Exoplanet TRAPPIST-1 e
Scientists are in the midst of observing the exoplanet TRAPPIST-1 e with NASA’s James Webb Space Telescope. Careful analysis of the results so far presents several potential scenarios for what the planet’s atmosphere and surface may be like, as NASA science missions lay key groundwork to answer the question, “are we alone in the universe?”
“Webb’s infrared instruments are giving us more detail than we’ve ever had access to before, and the initial four observations we’ve been able to make of planet e are showing us what we will have to work with when the rest of the information comes in,” said Néstor Espinoza of the Space Telescope Science Institute in Baltimore, Maryland, a principal investigator on the research team. Two scientific papers detailing the team’s initial results are published in the Astrophysical Journal Letters.
Image A: Trappist-1 e (Artist's Concept)
Of the seven Earth-sized worlds orbiting the red dwarf star TRAPPIST-1, planet e is of particular interest because it orbits the star at a distance where water on the surface is theoretically possible — not too hot, not too cold — but only if the planet has an atmosphere. That’s where Webb comes in. Researchers aimed the telescope’s powerful NIRSpec (Near-Infrared Spectrograph) instrument at the system as planet e transited, or passed in front of, its star. Starlight passing through the planet’s atmosphere, if there is one, will be partially absorbed, and the corresponding dips in the light spectrum that reaches Webb will tell astronomers what chemicals are found there. With each additional transit, the atmospheric contents become clearer as more data is collected.
Primary atmosphere unlikely
Though multiple possibilities remain open for planet e because only four transits have been analyzed so far, the researchers feel confident that the planet does not still have its primary, or original, atmosphere. TRAPPIST-1 is a very active star, with frequent flares, so it is not surprising to researchers that any hydrogen-helium atmosphere with which the planet may have formed would have been stripped off by stellar radiation. However many planets, including Earth, build up a heavier secondary atmosphere after losing their primary atmosphere. It is possible that planet e was never able to do this and does not have a secondary atmosphere. Yet researchers say there is an equal chance there is an atmosphere, and the team developed novel approaches to working with Webb’s data to determine planet e’s potential atmospheres and surface environments.
World of (fewer) possibilities
The researchers say it is unlikely that the atmosphere of TRAPPIST-1 e is dominated by carbon dioxide, analogous to the thick atmosphere of Venus and the thin atmosphere of Mars. However, the researchers also are careful to note that there are no direct parallels with our solar system.
"TRAPPIST-1 is a very different star from our Sun, and so the planetary system around it is also very different, which challenges both our observational and theoretical assumptions,” said team member Nikole Lewis, an associate professor of astronomy at Cornell University.
If there is liquid water on TRAPPIST-1 e, the researchers say it would be accompanied by a greenhouse effect, in which various gases, particularly carbon dioxide, keep the atmosphere stable and the planet warm.
“A little greenhouse effect goes a long way,” said Lewis, and the measurements do not rule out adequate carbon dioxide to sustain some water on the surface. According to the team’s analysis, the water could take the form of a global ocean, or cover a smaller area of the planet where the star is at perpetual noon, surrounded by ice. This would be possible because, due to the TRAPPIST-1 planets’ sizes and close orbits to their star, it is thought that they all are tidally locked, with one side always facing the star and one side always in darkness.
Image B: TRAPPIST-1 e Transmission Spectrum (NIRSpec)
Innovative new method
Espinoza and co-principal investigator Natalie Allen of Johns Hopkins University are leading a team that is currently making 15 additional observations of planet e, with an innovative twist. The scientists are timing the observations so that Webb catches both planets b and e transiting the star one right after the other. After previous Webb observations of planet b, the planet orbiting closest to TRAPPIST-1, scientists are fairly confident it is a bare rock without an atmosphere. This means that signals detected during planet b’s transit can be attributed to the star only, and because planet e transits at nearly the same time, there will be less complication from the star’s variability. Scientists plan to compare the data from both planets, and any indications of chemicals that show up only in planet e’s spectrum can be attributed to its atmosphere.
“We are really still in the early stages of learning what kind of amazing science we can do with Webb. It’s incredible to measure the details of starlight around Earth-sized planets 40 light-years away and learn what it might be like there, if life could be possible there,” said Ana Glidden, a post-doctoral researcher at Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Research, who led the research on possible atmospheres for planet e. “We’re in a new age of exploration that’s very exciting to be a part of,” she said.
The four transits of TRAPPIST-1 e analyzed in the new papers published today were collected by the JWST Telescope Scientist Team’s DREAMS (Deep Reconnaissance of Exoplanet Atmospheres using Multi-instrument Spectroscopy) collaboration.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
Quelle: NASA
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Update: 27.09.2025
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James Webb Space Telescope peers deep into the heart of star formation in our Milky Way galaxy
This massive star-forming cloud is working surprisingly fast.
A maelstrom of star formation close to the center of our galaxy has been revealed in two different wavelengths by the James Webb Space Telescope (JWST), its beautiful images highlighting the intensity of star-birth in the region and deepening the mystery of why star formation at the very heart of our galaxy is so sluggish.
Sagittarius B2 is a dense cloud of molecular gas located about 390 light-years from the black hole Sagittarius A* at the center of our Milky Way galaxy. At about 150 light-years across and containing enough gas to assemble 3 million sun-like stars, B2 is the largest, most massive and most active star-forming region in our entire galaxy.
Yet, B2 is at odds with the rest of the galactic center. As massive as B2 is, it contains only 10% of the molecular gas in the galactic center, gas that forms the building blocks of stars. Still, despite only having a modest fraction of gas relative to the galactic center as a whole, B2 produces half of all the stars there. It is an enduring mystery why B2 has such intense star formation while the rest of the galactic center has proportionately lower rates of star-birth.
That's why the new observations by the JWST are so important in understanding what drives and what puts the brakes on star formation in the galactic center.
"Webb's powerful infrared instruments provide detail we've never been able to see before, which will help us to understand some of the still-elusive mysteries of massive star formation and why Sagittarius B2 is so much more active than the rest of the galactic center," said study co-author Adam Ginsburg of the University of Florida in a statement.
One theory is that powerful, complex magnetic fields that are entwined around the galactic center and its retinue of molecular clouds similar to B2 could play a deciding factor, but the hows and whys there are still to be determined.
For its part, JWST can get to the heart of the star formation in B2 thanks to the space telescope's powerful infrared vision that can peer through much of the obscuring dust in the cloud. Presented here are two images, one taken at shorter infrared wavelengths by the JWST's Near Infrared Camera (NIRCam) and the other captured at longer wavelengths by the telescope's Mid-Infrared Instrument (MIRI).
JWST's mid-infrared view of Sagittarius B2, showing more extensive, dusty nebulosity being illuminated by newly born stars. (Image credit: NASA/ESA/CSA/STScI/Adam Ginsburg (University of Florida)/Nazar Budaiev (University of Florida)/Taehwa Yoo (University of Florida)/Image Processing: Alyssa Pagan (STScI).)
In the NIRCam image, we see myriad stars in B2 amid hazy patches of nebulosity. In the darkest areas where we can't see nebulosity there is cosmic dust too dense even for NIRCam to see through.
So, we turn to MIRI's image, which is able to penetrate the thicker dust in B2. Here, all but the brightest stars have faded to invisibility since they do not radiate much at these long infrared wavelengths. Meanwhile, the nebulosity across the entire scene has blossomed into life, revealing the true scale of star-birth in the region as each of those bright clouds is being illuminated by the light of very young but massive stars that are still in the process of growing.
The aim of the JWST observations is to better understand the history of star formation in B2. Has it been ongoing for many millions of years and many generations of stars, or has it only recently ignited? The answer will help place B2 into context with the rest of the galactic center as astronomers search for clues as to what stifles star-birth at the heart of our galaxy.
The findings could have broader repercussions. The intensity of star formation in B2 is believed by astronomers to be similar to conditions in the early universe when the first stars were formed in a flurry of frenzied activity. By learning what governs star formation in the galactic center, we could also be learning about what governed star formation in the aftermath of the Big Bang.
A study about these results can be viewed on the paper repository arxiv.
Quelle: SC