A Fossil Star Without Planets? A High-Precision Look at BD+44°493
BD+44°493 is an ancient, extremely metal-poor star whose chemistry preserves the imprint of a single early-Universe supernova. Using new high-precision NEID spectra, the authors refined its elemental abundances, age, and Galactic orbit, confirming it as a second-generation star about 12–13 billion years old. Ultra-precise radial velocities show no evidence of planets and rule out companions more massive than ~2 Jupiter masses on short orbits.
Ancient Relics in the Milky Way: The DECam MAGIC Survey Uncovers the Galaxy’s Most Metal-Poor Stars
Vinicius Placco and collaborators used the DECam MAGIC Survey to identify six extremely metal-poor stars in the distant Milky Way halo, including one ultra metal-poor star. Spectroscopic analysis confirmed their low metallicities and revealed one likely formed from a single early supernova. The study validates MAGIC’s photometric methods and shows how such stars trace the Galaxy’s earliest chemical enrichment and evolutionary history.
Relics of the First Galactic Core: How the Milky Way’s Oldest Stars Reveal Its Fiery Beginnings
Sun et al. map over five million metal-poor stars to uncover the Milky Way’s earliest structure. Using both observations and simulations, they find that the Galaxy’s oldest stars likely formed during high-redshift gas “compaction” bursts over 12 billion years ago. These events created a dense, non-rotating core, the proto-Galaxy, that later evolved into the Milky Way’s central bulge and thick disk.
A Star from Another Galaxy: The Most Pristine Relic of the Early Universe
Astronomers led by Alexander Ji discovered SDSS J0715−7334, the most metal-poor star ever found, originating from the Large Magellanic Cloud. Its composition suggests it formed from gas enriched by a single massive Population III supernova, revealing how early stars seeded the universe with heavy elements. This discovery provides a rare local glimpse into the universe’s first generations of stars.
Tracking Potassium in the Oldest Stars: What It Tells Us About Stellar Explosions
Miho Ishigaki and collaborators measured potassium in extremely metal-poor stars using the Subaru Telescope. They found that potassium-to-iron and potassium-to-calcium ratios were consistently enhanced with little scatter, unlike sodium-to-magnesium ratios, which varied widely. These results suggest potassium is produced through stable processes in massive stars and supernovae, making it a valuable tracer of how the earliest stars ended their lives.
Stellar Fossils from the Outer Halo: Exploring the Most Metal-Poor Stars with the DECam MAGIC Survey
Astronomers used the DECam MAGIC survey to identify six extremely metal-poor stars in the Milky Way’s outer halo, confirming their properties with high-resolution spectroscopy. One star, J0433–5548, stands out as a carbon-enhanced ultra metal-poor star likely formed from a single Population III supernova. These discoveries help trace the chemical evolution of the early universe and validate photometric selection methods.
Mapping the Metal of the Milky Way: How Gaia’s Spectra Help Us Understand Giant Stars
This study uses Gaia XP spectra and a neural network model (UA-CSNet) to estimate the metallicities of 20 million giant stars. The model is especially accurate for very metal-poor stars and provides reliable uncertainty estimates. Results align well with other datasets and reveal chemical patterns across the Milky Way.
Galactic Fossils: Exploring the Most Metal-Poor Stars in the Universe
This paper reviews the search for and study of the most metal-poor stars, which serve as relics from the early universe. These stars reveal clues about the first stellar generations and galaxy formation. The authors discuss how they’re found, what their chemical patterns tell us, and how their lithium levels challenge cosmological models.
Exploring the Kinematics of Omega Centauri’s Metallicity Populations
Vernekar et al. (2025) investigate the motions of different metallicity populations in Omega Centauri using Gaia and Hubble data. They find no significant differences in movement between metal-rich and metal-poor stars, suggesting that all populations are well-mixed. The study also confirms that Omega Cen rotates uniformly. These findings challenge the idea that metal-rich stars were accreted and instead support a self-enrichment scenario for the cluster’s formation.
Tracing the Past: The Ancient Metal-Poor C-19 Stellar Stream Extends Over 100 Degrees
The C-19 stellar stream, one of the most metal-poor structures in the Milky Way, has been found to extend over 100 degrees in the sky. Using Gaia data and advanced algorithms, researchers identified 12 new members, confirming its ancient origins. The stream is wider and more dynamically hot than expected, suggesting early disruption by dark matter or stellar interactions. These findings provide new insights into the formation of the first stellar structures in our galaxy.
Unveiling the Stars: Using Machine Learning to Map Stellar Parameters for 21 Million Stars
Astronomers used machine learning to estimate stellar parameters for 21 million stars from photometric data. Combining SAGES, Gaia, 2MASS, and WISE datasets, they achieved high precision in temperature, metallicity, and surface gravity measurements. This catalog offers new insights into the Milky Way and metal-poor stars, expanding future research possibilities.
The Mystery of Wide Binaries in Metal-Poor Stars
This study examines the frequency of wide binary companions among metal-poor stars using Gaia and infrared surveys. Researchers found that while close binaries (separations <8 AU) are common (about 20%), wide binaries (separations >8 AU) are rare, with a frequency below 3%. This suggests that metal-poor environments and dynamical interactions disrupt wide binaries over time. The findings provide insights into star formation in the early universe.
A Starburst in the Early Milky Way: A New Look at Our Galaxy’s Beginnings
A recent study led by Boquan Chen reveals that the early Milky Way experienced a massive starburst around 13 billion years ago, triggered by a rapid inflow of gas. By analyzing metal-poor stars from Gaia data, researchers found evidence of two distinct stellar populations, suggesting a sharp transition in star formation history. Their findings, supported by galaxy simulations, show that the Milky Way’s formation was not gradual but included bursts of intense star formation, shaping its present structure.
Discovering the Secrets of the Universe's Oldest Stars
The study provides the first framework for understanding extremely metal-poor (XMP) OB stars, key to exploring the early Universe. Using theoretical models, it calibrates stellar properties like temperature and ionizing photon flux, revealing XMP stars are hotter, more compact, and emit more ionizing radiation than their metal-rich counterparts. These findings aid in studying star formation and reionization in distant galaxies.
Exploring the Metal-Poor Stream C-19: A Glimpse into Galactic Formation
The C-19 stellar stream, the most metal-poor known, may originate from a disrupted globular cluster or dwarf galaxy. Researchers confirmed its uniform metallicity and velocity dispersion, challenging existing formation theories. The findings highlight C-19's potential as a key to understanding early galactic evolution.
The Hottest Neptunes: Exploring Planet Formation in Metal-Rich Systems
The study explores "Neptune desert" planets—rare, close-orbiting worlds between Neptune and Saturn in size—and finds they orbit metal-rich stars. These planets likely formed from gas giants that lost their outer layers, as their host stars' metallicities resemble those of hot Jupiter hosts. The findings challenge other formation theories, offering new insights into planetary evolution near stars.
Tracing the Origins of Alpha-Poor, Very Metal-Poor Stars
Alpha-poor very metal-poor stars are rare stars with unique chemical signatures, primarily explained by core-collapse supernova ejecta. Some stars also show contributions from sub-Chandrasekhar Type Ia supernovae. Pair-instability supernovae play a minimal role, highlighting the diversity of processes shaping early cosmic chemical evolution.
Unveiling the Chemical Legacy of the Sagittarius Dwarf Galaxy
The study examines the Sagittarius dwarf galaxy (Sgr dSph), revealing its star formation history and chemical evolution through high-resolution spectroscopy of 111 giant stars. The findings highlight a slower star formation rate compared to the Milky Way, distinct elemental patterns from neutron-capture processes, and contributions from ancient and younger stellar populations. Sgr's evolution offers insights into galactic mergers and enrichment in the Milky Way's halo.
Revealing the Coldest: Investigating the Metal-Poor T and Y Dwarf Populations
The study explores the coldest metal-poor T and Y dwarfs, expanding their optical dataset and refining parallax measurements. It confirms "The Accident" as a Y subdwarf and highlights discrepancies in theoretical models predicting metallicity effects on colors. These findings enhance understanding of ancient stellar populations and inform future atmospheric modeling and surveys.
Unveiling the Secrets of Metal-Poor Stars: Tracing Single Supernova Enrichment
Yutaka Hirai and colleagues used simulations to study mono-enriched stars, which form from a single supernova's ejecta. They found these stars are rare, with higher fractions at lower metallicities, and mostly form early in a galaxy's history near its center. This work provides new insights into early star formation and nucleosynthesis, with future observations expected to confirm these predictions.