Heavy Elements in a Swirling Storm: How Neutron Stars Inside Common Envelopes Forge the Universe’s Rarest Atoms
Anninos et al. model how a neutron star inside a common envelope can forge heavy elements as infalling gas heats, cools, and cycles through turbulent convection. Their simulations show that both r-process and rare p-nuclei can form, even in slightly proton-rich conditions, because high entropy and rapid expansion prevent neutrons from being fully locked into alpha particles. Some material escapes the star’s gravity, suggesting CE systems may contribute to the Universe’s heaviest elements.
Trading Oxygen for Iron: Rethinking How the Universe Built Its Stars
The paper argues that oxygen and iron trace galaxy evolution very differently because they form on different timescales. Using a new [O/Fe]–sSFR relation, the authors show that most stars formed with non-solar O/Fe, especially in the early universe. Their iron-based cosmic star formation history aligns with RR Lyrae, globular cluster, and GRB-host data, highlighting that models assuming solar abundance patterns often misrepresent real cosmic conditions.
Tracing the Chemistry of Massive Stars Before They Shine: A Tour Through High-Mass Star-Forming Regions
High-mass stars form in dense, distant, and fast-evolving environments that produce distinct chemical signatures. The chemistry progresses from simple, highly deuterated molecules in cold starless cores to rich complex organic molecules in warmer protostellar objects, then becomes dominated by ultraviolet-driven processes in H II regions. Upcoming ALMA and JWST observations are expected to clarify this chemical evolution and its implications for star and planet formation.
Learning the Chemistry of Stars Without Models: A New Way to Spot Unusual Stars
Theosamuele Signor and collaborators present a neural network that learns stellar chemical abundances directly from spectra without using theoretical models. Using a variational autoencoder, the model isolates chemical information for iron, carbon, and α-elements, successfully identifying unusual stars like CEMP and αPMP types. This data-driven, model-free approach could transform how astronomers study stellar chemistry and the Milky Way’s history.
JWST Uncovers a Carbon-Rich Planet-Forming Disk Around a Young Star
JWST observations of the transitional disks GM Aur and J1615 reveal that, despite their similar stars, the two systems have strikingly different inner-disk chemistry. J1615 hosts abundant carbon-rich molecules, while GM Aur shows mostly water and OH. The authors suggest that J1615’s low accretion rate and more processed dust help preserve carbon-bearing gas, highlighting how small physical differences can dramatically alter planet-forming environments.
Tracing the Galactic Past: Chemical Clues from the Milky Way’s Faint Companions
Cheng Xu and collaborators used APOGEE data to study the chemical makeup of four dwarf galaxies orbiting the Milky Way. They found that galaxy mass influences how elements like magnesium and iron evolve over time, with larger galaxies retaining alpha elements longer. In Fornax, they discovered nitrogen-rich stars likely from disrupted globular clusters, offering clues about early star formation and galactic evolution.
When Metals Shape the Stars: How Chemical Yields Define Galactic Identities
Jason L. Sanders presents analytic models showing how metallicity-dependent stellar yields explain differences between galactic populations. By treating metal-dependent production as a built-in “delay time,” the models reveal why elements like aluminum trace star formation efficiency and outflows. Comparing predictions with APOGEE data, Sanders demonstrates that such yields naturally separate in-situ and accreted stars, offering a clear, mathematical framework for galactic chemical evolution.
Tracing Cosmic Origins: Europium in the Small Magellanic Cloud
Anoardo et al. present the first large survey of europium in 209 stars of the Small Magellanic Cloud, tracing how heavy elements formed there. They find the SMC has high [Eu/Mg] ratios, signifying strong r-process enrichment, compared to the Milky Way. This suggests dwarf galaxies produce europium more efficiently due to slower star formation, offering key insight into how such systems contributed heavy elements to our Galaxy.
Tracing the Origins of the Universe’s Heaviest Elements: The R-Process Alliance Examines Ten Ancient Stars
Racca et al. (2025) studied ten ancient, r-process-enriched stars to uncover how the universe creates its heaviest elements. Using high-resolution spectroscopy, they found nearly identical abundance patterns across stars from distinct origins, with minimal variation (<0.1 dex). This surprising uniformity suggests that r-process nucleosynthesis, likely from neutron-star mergers or similar extreme events, follows a consistent, universal mechanism throughout cosmic history.
Tracing Planet Formation Through Stellar Fingerprints: A Spectroscopic Look at C/O Ratios in Directly Imaged Exoplanet Hosts
Baburaj et al. conducted a high-resolution spectroscopic survey of five stars hosting directly imaged exoplanets to measure their elemental abundances. They found solar-like C/O ratios for HR 2562, AB Pic, and YSES 1, but significantly sub-solar ratios for PZ Tel and β Pictoris. These differences suggest diverse formation environments and highlight how stellar chemistry can trace planet formation processes.
Barium Clues: Unraveling the Origins of Carbon-Enhanced Ancient Stars
Sitnova et al. studied ten carbon-enhanced metal-poor stars to measure their barium isotope ratios. They found that CEMP-s stars have isotope patterns consistent with the slow neutron-capture (s-) process, while CEMP-rs stars show signatures matching the intermediate (i-) process. This distinction suggests that the i-process, rather than a mix of s- and r-processes, shaped the chemical makeup of many CEMP-rs stars.
Tracing the Chemistry of Exoplanet Hosts: What K2 Stars Reveal About Planets and Their Parent Stars
Loaiza-Tacuri et al. analyzed 301 K2 exoplanet-hosting stars using high-resolution spectra to measure stellar temperatures, metallicities, magnesium abundances, and activity levels. They confirmed the planetary radius gap near 1.9 R⊕, found that larger planets orbit more metal-rich stars, and showed stellar activity decreases with planet size. Most hosts belong to the Galactic thin disk, linking stellar chemistry to planetary formation.
Uncovering the Chemical Story of Star-Birth Rings in Nearby Galaxies
Eva Sextl and Rolf-Peter Kudritzki use MUSE data to study four spiral galaxies with bright nuclear star-forming rings. By separating young and old stellar populations, they find that these rings are metal-rich, not metal-poor as once thought. Their new “physical metallicity” method reveals that inflows of fresh gas and repeated star formation cycles drive long-term chemical enrichment in galactic centers.
Mapping the Life and Legacy of Dying Stars: How Planetary Nebulae Reveal the Milky Way’s Chemistry
N. Erzincan and colleagues analyzed 1,449 planetary nebulae to explore how dying stars shape the Milky Way’s chemistry. Using spectra from the HASH database and Gaia distances, they measured temperatures, densities, and elemental abundances. Disk nebulae were richer in heavy elements than those in the halo, and sulfur and nitrogen showed a strong correlation, revealing links between stellar evolution and Galactic chemical enrichment.
Mapping Metal and Molecule Mysteries in Interstellar Comet 3I/ATLAS
Hoogendam et al. (2025) used the Keck Cosmic Web Imager to study interstellar comet 3I/ATLAS, confirming gas emissions from cyanogen (CN) and nickel (Ni). They found Ni concentrated closer to the nucleus, suggesting it originates from short-lived compounds like metal carbonyls or organics. The findings indicate that interstellar comets may be metal-rich but water-poor, offering clues about the chemistry of distant planetary systems.
Tracing Starlight: How Ultraviolet Observations Reveal the Heavy Elements in HD 196944
Roederer et al. used ultraviolet spectra from the Hubble Space Telescope to study HD 196944, a carbon-enhanced metal-poor star rich in s-process elements. They detected 35 heavy elements, the most ever found in such a star, and showed these likely came from a former AGB companion. Their results confirm that UV spectroscopy can reveal new details about how stars create the universe’s heaviest elements.
Unearthing a Disequilibrium: JWST Unveils Methane and Carbon Monoxide in 51 Eridani b
Using JWST’s NIRSpec, Madurowicz et al. directly detected methane and carbon monoxide in the atmosphere of the exoplanet 51 Eridani b, confirming chemical disequilibrium caused by atmospheric mixing. Their high-resolution spectra revealed a 4.8σ planetary signal and an atmosphere that is partly cloudy, metal-rich, and about 800 K. This marks JWST’s first direct confirmation of multiple molecules in a cool, Jupiter-like exoplanet.
Tracing Stellar Mergers with Chemistry: Carbon Isotopes Reveal Clues to Mysterious Stars
Astronomers studied massive α-enriched (MAE) stars, which look chemically old but appear too massive to be ancient. By measuring carbon isotope ratios (¹²C/¹³C), Zachary Maas and collaborators found most MAE stars resemble thick disk stars, while a few show evidence of mass transfer or mergers. The results suggest MAE stars form through multiple pathways, with carbon isotopes serving as key clues to their hidden histories.
Makemake’s Hidden Activity: JWST Finds Methane Gas and Hydrocarbon Ices
JWST observations show that Makemake’s surface holds methane, ethane, acetylene, and possibly methanol, arranged in layered ices. The telescope also detected methane gas, either from a thin atmosphere or plume-like outgassing. These findings suggest Makemake is more active and chemically complex than once thought, challenging its image as a frozen, inactive world.
A Closer Look at Carbon-Chain Depleted Comets
Allison Bair and David Schleicher analyzed 17 strongly carbon-chain depleted comets using Lowell Observatory’s long-term photometry database. These comets, mostly Jupiter-family objects, show far lower levels of C₂ and C₃ (and sometimes NH) compared to typical comets, though their dust-to-gas ratios are similar. The authors argue this depletion reflects primordial formation conditions in the Kuiper Belt, rather than later heating in the inner Solar System.