Mapping the Milky Way’s Hidden Superclouds
Kormann et al. use new Gaia-based 3D dust maps to identify seven massive, kiloparsec-long superclouds in the local Milky Way. These structures are highly elongated, mostly parallel, and contain most nearby star-forming regions. Many show vertical undulations, and despite differing masses, they maintain similar densities, suggesting pressure-regulated formation driven by large-scale Galactic dynamics rather than spiral arms.
A Giant, Slow-Motion Bubble: Tracing a Long-Lived Superbubble Across the Perseus Arm
This paper studies the Giant Oval Cavity, the largest known superbubble in the Milky Way, stretching across the Perseus spiral arm. By tracking the motions of young, massive stars, the authors show that the cavity is slowly expanding and extremely long-lived. Repeated supernova explosions continually supply energy, allowing the structure to survive despite Galactic turbulence and shear.
Riding the Galaxy’s Carousel: Measuring the Milky Way’s Rotation with Gaia Cepheids
Feng and collaborators use nearly a thousand Gaia DR3 Classical Cepheids to measure the Milky Way’s rotation curve with high precision. They find a gently declining trend with a distinct dip and bump, features seen mostly in young tracers. By constructing an averaged rotation curve, they estimate a solar circular speed of about 237 kilometers per second and derive dark matter densities and masses consistent with previous studies.
Mapping Our Stellar Neighborhood: What Nearby Stars Reveal About the Milky Way
This paper combines Gaia and GALAH DR4 data to study about 6,000 stars within 100 pc of the Sun. The authors find that the local stellar population is dominated by FGK main-sequence stars with a median age of ~1.6 Gyr and slightly sub-solar metallicity. Most stars belong to the Galactic disc, with only a small halo component, setting the stage for future detailed chemo-dynamical studies.
Mapping Our Galaxy in Unprecedented Detail: Why the Milky Way Needs a New Stellar Census
The paper argues that fully understanding how the Milky Way formed requires a new, Galaxy-wide map that combines stellar motions, chemistry, and ages. Current and planned surveys lack the precision and coverage needed, especially in the disc midplane and bulge. The authors propose a future large spectroscopic facility to finally reconstruct the Milky Way’s formation and evolution in detail.
Building the Milky Way: How Gas, Chemistry, and New Telescopes Reveal Our Galaxy’s Hidden Structure
The paper reviews how gas in the Milky Way gathers and changes chemically to form stars, using (sub-)millimeter spectral lines to trace physical conditions from giant molecular clouds down to star-forming cores. It highlights limits of current surveys and argues that new facilities and layered Galactic Plane surveys are essential to fully understand mass assembly, star formation, and chemical complexity in our Galaxy
Mapping the Milky Way in Motion: Revealing the Galaxy’s Six-Dimensional Skeleton of Star Formation
This White Paper argues that the Milky Way should be understood as a dynamic system, where star formation is shaped by large-scale motions such as warps and waves in the Galactic disk. By building a six-dimensional map of young stars, combining positions, motions, and ages, the authors aim to link Galactic dynamics to how and where stars form. Achieving this requires future deep surveys and new spectroscopic facilities to reveal the Galaxy’s hidden structure.
Tracking Carbon Through the Milky Way: What the Stars Tell Us About How Carbon Forms
The paper investigates how carbon is produced in the Milky Way by comparing chemical evolution models with APOGEE observations of subgiant stars. The authors find that massive stars must produce more carbon at higher metallicity, while AGB stars contribute a delayed but significant fraction, about 10–40% of the Sun’s carbon. Their results suggest that current AGB models may underestimate carbon production from lower-mass, longer-lived stars.
The Milky Way’s Peculiar Primordial Halo: A Shallow Core with a Steep Decline
Li et al. (2025) use Gaia data and a numerical “reverse–compression” method to infer the Milky Way’s primordial dark matter halo. They find an unusual structure: a shallow inner core and a steep outer decline, unlike halos predicted by standard cold dark matter models. Neither baryonic feedback nor alternative dark matter models fully explains this combination, suggesting gaps in current theories of dark matter or galaxy formation.
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.
Peering Past the Galactic Bar: Uncovering a Hidden Spiral Arm in the Milky Way
Simran Joharle and collaborators analyzed red clump stars near the Milky Way’s center using motion and dust data from the VVV survey. They found that one group of stars lies farther away and moves differently, consistent with Galactic rotation. Slightly higher extinction toward this group suggests it belongs to a spiral arm beyond the Galactic bar, providing new insight into the Galaxy’s hidden structure.
Unraveling the Milky Way’s Past: Tagging Stellar Substructures with Chemistry and Motion
Kristopher Youakim and Karin Lind used a new chemo kinematic tagging method combining stellar motions and chemical compositions to trace the Milky Way’s merger history. Using data from over 5000 stars, they identified known structures like Gaia Sausage Enceladus and Sequoia, linked many globular clusters to past mergers, and revealed new connections such as between the Orphan Chenab stream and Grus II dwarf galaxy.
Tracing the Ghosts of Clusters: StarStream Reveals Hidden Stellar Streams in the Milky Way
Yingtian Chen and colleagues used their new algorithm, StarStream, to uncover 87 stellar streams from globular clusters in Gaia data, doubling the known number. The method detects even irregular, misaligned streams, revealing that many clusters are actively losing stars. Measured mass loss rates show that low-mass, extended clusters like Palomar 5 are nearing tidal disruption, offering fresh insights into the Milky Way’s evolution.
Mapping the Hidden Streams of the Milky Way: Correcting Bias in Dark Matter Searches
Boone et al. (2025) develop a method to correct biases in stellar stream observations caused by uneven survey conditions in the Dark Energy Survey. Using synthetic stars from the Balrog tool, they refine measurements of stellar densities, demonstrating the method on the Phoenix stream. Their corrections remove false patterns and improve dark matter studies, offering an essential approach for future deep surveys like LSST.
Mapping the Motion of the Milky Way’s r-Process Stars
Pallavi Saraf and collaborators studied how r-process-enhanced stars, those rich in heavy elements formed by rapid neutron capture, move through the Milky Way. Using Gaia data and orbital simulations, they found these stars are almost evenly split between the disk and halo. Most have uncertain origins, though halo stars are more likely accreted. Similar chemical patterns across regions suggest r-process enrichment occurred under comparable conditions throughout the Galaxy.
Tracing the Milky Way’s Past with HDBSCAN: Finding the Ghosts of Ancient Galaxies
Andrea Sante and collaborators test the HDBSCAN clustering algorithm to trace the Milky Way’s merger history using Auriga simulations. By optimizing parameters and using a 12-dimensional feature space, they show HDBSCAN reliably identifies recent stellar streams but struggles with older, well-mixed debris. Contamination from stars formed inside the Milky Way further limits recovery, though cluster purity remains high.
Do Most Stars Form in Clusters? A New Look at Our Galaxy’s Star Birthplaces
Quintana and collaborators used new Gaia data to show that most stars in the Milky Way likely form in compact clusters. Their calculations suggest that at least half, and probably over 80%, of stars are born this way, much higher than past estimates. This supports the clustered star formation model, though many clusters dissolve quickly, leaving stars spread across the Galaxy.
Survivors and Zombies: How the Milky Way Built Its Satellite Family
Pathak and collaborators use high-resolution simulations to study why some dwarf galaxies around the Milky Way survive while others are destroyed. They find that survival depends on mass, time of infall, and orbit: massive satellites usually disrupt before quenching, while tiny ultra-faint dwarfs quench early but endure. Disrupted galaxies often kept forming stars until the moment of destruction, helping to explain the mix of surviving satellites and stellar debris in the Milky Way halo.
Galactic Encounters: What TNG50 Reveals About the Milky Way’s Dance with Sagittarius
Using the TNG50 simulation, researchers studied galaxy interactions similar to that between the Milky Way and Sagittarius. They found that such encounters rarely disturb the host galaxy’s vertical stellar motions or trigger star formation, unless the galaxy was already unusually cold or inactive. Most Milky Way-like discs were already perturbed, raising questions about how common this disequilibrium is in the universe.
Is the Milky Way Really Slowing Down? A Closer Look at the Galaxy’s Rotation Curve
Klacka and Šturc argue that recent claims of a declining Milky Way rotation curve result from using incorrect equations suited for flat disks, not spherical systems. When the correct spherical models are applied, the rotation curve appears flat, consistent with other spiral galaxies, suggesting no unusual drop in velocity or dark matter content.