ALMA's Milky Way image reveals galactic center

Lead

On 26 February 2026 scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile released the largest-ever ALMA image of the Milky Way’s central region. The mosaic, produced by an international team led by Steven Longmore of Liverpool John Moores University, maps dense gas and star-forming material across the galaxy’s core with unprecedented continuity. The dataset exposes long, narrow filaments of gas and new patterns of connection between clouds previously seen as isolated patches. Researchers say the image provides a nearby laboratory for processes that were common when the universe made most of its stars.

Key Takeaways

ALMA produced its largest-ever mosaic of the Milky Way’s central molecular zone (CMZ), released 26 February 2026.
The survey involved more than 160 researchers working on the ALMA CMZ Exploration Survey over several years.
Scientists discovered extended, thin filaments channeling gas across the CMZ—structures not apparent in prior, patchy observations.
Project lead Steven Longmore (Liverpool John Moores University) says the CMZ conditions resemble high-redshift star-forming galaxies, allowing detailed study of star and planet formation locally.
The team has applied for follow-up observations with the James Webb Space Telescope and the Extremely Large Telescope; Webb time is highly competitive and currently oversubscribed.
The image blends aesthetic detail with measurable physical signatures—temperature, density, and turbulent motion—useful for quantitative modeling.

Background

The Milky Way’s central molecular zone (CMZ) sits within the innermost few hundred parsecs of our galaxy and hosts extreme temperatures, pressures and turbulent motions compared with the solar neighborhood. Those conditions make it a natural analog to the gas-rich galaxies of the early universe, where most stellar mass formed but which lie too distant for resolved study. ALMA, an array of radio dishes on the Chajnantor plateau in Chile, is uniquely sensitive to the cold dust and molecular gas that trace where stars will form.

Before this survey, observations of the CMZ consisted of isolated pointings and small mosaics that revealed pockets of gas and individual star-forming clouds but left the larger connectivity unclear. That fragmentation of datasets limited researchers’ ability to trace flows of matter across multiple cloud systems and to test which interactions trigger collapse. The ALMA CMZ Exploration Survey was designed to produce a continuous, high-resolution map to close that gap.

Main Event

The ALMA team combined many pointings into a single, very large mosaic covering the central region coordinated under the ALMA CMZ Exploration Survey. The processed image preserves fine spatial structure while linking features across large angular scales, enabling scientists to follow gas from extended streams into dense cores. Longmore and collaborators report that, rather than a random tangle, the center shows coherent filamentary streams that appear to feed mass toward star-forming sites.

Researchers describe the filaments as long, thin conduits of molecular gas whose orientation and continuity suggest organized flows rather than isolated clouds. In interviews, Longmore emphasized that seeing how clouds connect was the critical advance: previous data were like snapshots of streets; the new map is closer to a city plan showing how traffic moves. The discovery was described as unexpected because such extended filaments were not obvious in earlier, sparser surveys.

Beyond morphology, the image contains measurable observables—line emission tracing gas velocity and density contrasts—that let teams estimate inflow rates, compression events, and potential triggers of star formation. The group plans to combine the ALMA data with observations at infrared and optical wavelengths to test whether collisions or other dynamical processes compress gas enough to form stars. The team has applied for James Webb Space Telescope and future Extremely Large Telescope time to add complementary wavelength coverage; Webb proposals are highly oversubscribed, the team notes.

Analysis & Implications

Using the CMZ as a proximate analogue of high-redshift star-forming environments is a powerful approach because the physics—strong turbulence, high pressures, intense radiation fields—overlap with conditions in early galaxies. If the filaments identified by ALMA indeed channel gas into sites of star formation, they provide a mechanistic link between galactic dynamics and the local collapse of gas into stars and planets. That would tighten constraints on models that currently rely on statistical correlations drawn from unresolved, distant galaxies.

Combining ALMA’s millimeter view with infrared imaging from JWST and high-resolution optical/near-infrared spectroscopy from the ELT would allow researchers to map star-formation history, identify young stellar populations, and measure feedback effects in situ. Multiwavelength datasets translate morphological impressions into cause-and-effect tests: for example, determining whether a collision between two flows preceded a burst of protostar formation in the same region. Such causal inference is central to distinguishing competing theoretical models of star formation under extreme conditions.

There are broader implications for galactic evolution. If coherent inflows are common in galactic centers, they can regulate nuclear star formation rates, influence black hole feeding, and shape central chemistry over cosmic time. Conversely, if the filaments are transient or locally driven by stellar feedback, their role in long-term galaxy evolution may be limited. Follow-up observations and numerical simulations will be required to evaluate these scenarios quantitatively.

Comparison & Data

Facility	Primary band(s)	Role for CMZ study
ALMA	Millimeter/submillimeter	Maps cold gas and dust, kinematics of molecular tracers
JWST	Near–mid infrared	Detects embedded young stars and warm dust, diagnostic lines
ELT (planned)	Optical/near infrared	High spatial resolution spectroscopy of stellar populations

Instrument strengths and complementary roles for studying the CMZ.

ALMA supplies the baseline map of cold gas morphology and velocity structure; JWST will reveal the embedded young stellar content and heating; ELT-class telescopes will deliver dynamical and chemical detail at fine spatial scales. Together these capabilities let teams test whether filaments feed star formation or are byproducts of local processes.

Reactions & Quotes

“The central regions of our galaxy act like a nearby laboratory for conditions that were common when most stars formed in the universe,”

Steven Longmore, Principal Investigator, Liverpool John Moores University

Longmore framed the image as both a scientific and aesthetic milestone: it links striking visual structure with quantitative physics that teams can analyze.

“This mosaic moves us from fragmented snapshots to a continuous map, revealing how gas is organized across the CMZ,”

ALMA Collaboration (project statement)

The ALMA collaboration emphasized the technical effort required to stitch many observations into a coherent, high-fidelity map and noted plans for coordinated follow-up.

“Combining facilities at different wavelengths will let us pin down which events actually trigger star formation,”

ALMA CMZ team spokesperson

Team members said multi-observatory campaigns are the logical next step, though scheduling on flagship telescopes is competitive.

Unconfirmed

Whether the observed filaments definitively drive mass flow that results in star formation remains to be proven; current evidence shows coherence but not final causation.
The team’s requests for JWST and ELT time are pending; allocation is not guaranteed and proposals face strong competition.
Detailed rates of mass transfer along filaments and long-term stability of these structures are not yet measured and require follow-up observations and modeling.

Bottom Line

The ALMA CMZ mosaic released on 26 February 2026 is a significant advance: for the first time ALMA maps the Milky Way’s center as a continuous system at high resolution, revealing long filaments and connections between star-forming regions. That spatial continuity turns previously isolated observations into a coherent picture that can be interrogated with physical measurements.

To convert morphological discovery into robust astrophysics, the community needs coordinated, multiwavelength follow-up and targeted simulations. If subsequent JWST and ELT observations confirm that filaments funnel gas into collapsing cores, the result will refine models of star and planet formation in extreme environments and improve our understanding of how galaxies built their stellar mass across cosmic time.

ALMA’s new image reveals Milky Way’s central structure in unprecedented detail