Digging for Cosmic Gold: Unveiling the Secrets of a Rare r-Process Star in the Ultraviolet
Hansen et al. analyze the metal-poor star J0538, revealing detailed abundances of 43 elements, including rare r-process products like gold and cadmium. Using UV observations from Hubble, they find unexpected star-to-star variation, suggesting non-LTE effects. Their findings support ongoing efforts to trace the cosmic origins of heavy elements and hint at the star’s possible origin in a disrupted dwarf galaxy.
When Bars Take Shape: Tracing the History of Galactic Bars Across Cosmic Time
This study presents the first large sample of bar age measurements in nearby galaxies, using nuclear discs to trace bar formation. The authors find that bars formed across a wide range of cosmic time and that older bars tend to be longer, stronger, and linked to reduced star formation. Surprisingly, bar age doesn’t correlate with galaxy mass, challenging the downsizing theory.
Aging Stars with Confidence: How Neural Networks and Uncertainty Help Date the Cosmos
This study introduces a Bayesian neural network model to estimate stellar ages using chemical abundance data. By modeling uncertainties directly, the approach yields accurate and cautious age predictions for main sequence stars, achieving errors under 1 billion years. It rivals traditional methods while offering flexibility and improved uncertainty handling, making it valuable for broader stellar and galactic studies.
Runaway Revelations: Tracking the Hidden Lives of Ejected Stars
This study presents a 13-year spectroscopic survey of 188 candidate runaway stars, revealing that over 40 are in binary systems and confirming that most have unusually high space velocities. By combining this data with Gaia measurements, the team improved velocity estimates and attempted to trace the stars' origins, though no definitive links to known neutron stars were found.
Namaka’s Shadow: Catching a Tiny Moon Eclipse a Distant Star
Astronomers observed the first stellar occultation by Namaka, a small moon of the dwarf planet Haumea, revealing a minimum size of 83 km. This rare event helps refine Namaka’s orbit and hints at Haumea’s internal structure. The study demonstrates how brief stellar eclipses by distant objects can uncover key details about our solar system’s outermost regions.
Painting the Chemistry of Star Clusters: Tracing the Origins of Stellar Populations through Light and Spectra
Dondoglio et al. combine photometry and spectroscopy to analyze chemical differences among stars in 38 globular clusters. They confirm widespread element variations between stellar populations and find strong links to cluster mass. Unexpected lithium patterns and chemically "anomalous" stars suggest complex formation histories. Their work offers new insights into how globular clusters evolved chemically over time.
A Stellar Blender: Black Holes May Be Pulverizing Stars at the Center of the Milky Way
Haas et al. propose that a dense cluster of stellar-mass black holes near the Milky Way’s center acts as a “star grinder,” destroying massive stars through collisions. This explains the absence of O-type stars in the S-cluster and matches observed star distributions. Their model also accounts for missing hypervelocity star counterparts and supports a peaked black hole density near Sgr A⋆.
Unveiling a Pulsating Pair: A Close Binary with a Pre-White Dwarf in WASP 1021-28
Lee et al. (2025) analyze the binary system WASP 1021-28, made up of an A-type star and a pre-He white dwarf. Using TESS and VLT data, they model the system’s physical properties and detect pulsations from both stars. Their results reveal insights into stellar evolution, binary interaction, and the role of a distant third star in shaping the system’s history.
Methane from the Beginning: A Primordial Origin for Methane on Eris and Makemake
Mousis et al. argue that the methane on Eris and Makemake likely formed in the early Solar System’s protosolar nebula, based on their high D/H ratios. Using disk chemistry models, they show that the methane’s isotopic signature matches a primordial origin, not internal production. This supports the idea that many outer Solar System bodies share common icy building blocks.
How Star Clusters Grow Old: Modeling the Formation and Evolution of the Milky Way’s Stellar Families
This study models how Milky Way star clusters form and evolve, focusing on how their masses change with age. Using data from the MWSC survey, the authors find that clusters lose most of their mass early on through a phase called violent relaxation. Their model matches observations well and suggests a constant cluster formation rate over billions of years.
Tracing the Origins of Globular Clusters Through Their Tidal Tails
Piatti analyzes simulated extra-tidal stars from Grondin et al. (2024) to test if they match real globular cluster tidal tails. While the tail widths align with in-situ formation, velocity dispersions suggest an external origin. The findings challenge assumptions about how stars escape clusters and imply that some clusters may have formed outside the Milky Way. This work highlights the need for refined simulations to better understand the galaxy’s history.
Massive Star Formation at the Edge of the Galaxy: The LZ-STAR Survey of Sh2-284
The LZ-STAR survey explores low-metallicity star formation in Sh2-284, focusing on the massive protostar S284p1. ALMA and JWST observations reveal a symmetric, parsec-scale bipolar outflow, suggesting an ordered formation process. S284p1, about 11 solar masses, has grown from a dense gas clump over 300,000 years. The findings show that massive stars can form in a structured way, even in environments with lower metal content, offering insights into early universe star formation.
Bright but Uncertain: Over-Luminous Type Ia Supernovae and Their Role in Cosmology
Over-luminous Type Ia supernovae are unusually bright stellar explosions that challenge their role as standard candles for measuring cosmic distances. This study analyzed eight such supernovae and found they yield a lower Hubble constant (H₀), aligning more closely with early-universe measurements. While this may help address the Hubble tension, it also raises concerns about the reliability of these supernovae in cosmology. Further research is needed to determine their true role in measuring the universe’s expansion.
Primordial Open Cluster Groups: The Role of Supernovae in Star Formation
Liu et al. (2025) identified four new open cluster (OC) groups using Gaia data and found evidence that supernova explosions triggered the formation of two groups (G1 and G2). Their simulations show OC groups gradually disperse over time. A clear age gradient and pulsar trajectories support the supernova-triggered star formation hypothesis. These findings reinforce the hierarchical star formation model, highlighting the role of stellar feedback in shaping star clusters in the Milky Way.
Exploring the Galactic Halo with RR Lyrae Stars
Cabrera Garcia et al. analyze over 135,000 RR Lyrae stars to study the Milky Way’s halo structure. They confirm the existence of inner and outer halo components and identify 97 dynamically tagged groups (DTGs) using motion-based clustering. Many DTGs align with known galactic substructures, such as Gaia-Sausage-Enceladus and the Helmi Stream, highlighting past galaxy mergers. Their findings reinforce the idea that the Milky Way’s halo formed through multiple accretion events.
How Do Galactic Bars Form? A Look at Tidal vs. Internal Growth
This study compares bars in galaxies that form internally versus those triggered by tidal interactions. Simulations show that tidal forces mainly affect when a bar forms, not how fast it grows, except in galaxies resistant to bar formation, where bars grow differently. Bars in naturally unstable galaxies follow the same growth pattern whether triggered externally or not, highlighting the dominance of a galaxy’s internal properties in shaping bar evolution.
The Youngest Star Clusters in the Large Magellanic Cloud
This study explores the youngest star clusters in the Large Magellanic Cloud using multi-wavelength data and machine learning techniques. Researchers identified clusters, estimated their ages and masses, and found a strong relationship between cluster mass and the most massive star, supporting the "optimal sampling" model of star formation. Their findings provide new insights into how stars form and evolve in dwarf galaxies, helping to refine our understanding of stellar and galactic evolution.
Mapping the Stars: A Catalog of Over 50 Million Stars from SMSS and Gaia
Yang Huang and Timothy C. Beers have compiled a catalog of stellar parameters for over 50 million stars using data from SMSS DR4 and Gaia DR3. This dataset provides accurate metallicity, temperature, and distance estimates, significantly expanding previous surveys. Their work is part of SPORTS, a project to catalog as many Milky Way stars as possible. The results will help astronomers study galactic evolution and the early universe.
Fluorescent Amino Acids on Europa: A Search for Life in the Ice
Europa's icy surface may contain fluorescent amino acids, potential biosignatures of life from its subsurface ocean. Scientists modeled how radiation and UV light degrade these molecules, finding that high-latitude regions offer the best preservation. A future spacecraft using laser-induced fluorescence could detect these compounds, especially in recently resurfaced ice or potential plumes. NASA’s Europa Clipper mission may help confirm whether Europa harbors the building blocks of life.
The Mass-Loss Mystery of Red Supergiants: Investigating Metallicity's Role
The study investigates whether the mass-loss rates of red supergiants (RSGs) depend on metallicity by analyzing thousands of RSGs across multiple galaxies. Results show no strong correlation between metallicity and mass loss, though a "kink" in the mass-loss relation shifts with metallicity. The findings suggest that other factors, like internal turbulence, may drive mass loss rather than metallicity. Future observations, especially with JWST, could clarify remaining uncertainties.