A Quiet Corner of the Milky Way Could Hold the Secret to Star Formation

This image shows the complex distribution of molecular gas in the Central Molecular Zone (CMZ) of the Milky Way. It was obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. This map is as long as three full Moons side-by-side in the sky, and it is in fact the largest ALMA image ever obtained. This map is part of ACES - the ALMA CMZ Exploration Survey - a project designed to understand how gas condenses into stars in the extreme and chaotic environment at the heart of our galaxy. The survey has charted the distribution of dozens of different molecules, five of which are shown here in different colours: sulphur monoxide (cyan), silicon monoxide (green), isocyanic acid (red), cyanoacetylene (blue), and carbon monosulphide (magenta). The stars in the foreground of this image were observed at infrared wavelengths (Y, Z and J filters) with ESO's VISTA telescope as part of a different project. The actual density of stars in the CMZ is much higher than what is shown here, where we have opted to highlight the details in the molecular cloud. Note that the edges of the ALMA map appear somewhat sharp because the ALMA observations do not cover the entire rectangular area here. Image credit: ALMA(ESO/NAOJ/NRAO)/S. Longmore et al. Background: ESO/D. Minniti et al.

ALMA scientists uncover a "calm island" of gas, suggesting star birth follows similar steps across the galaxy

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have identified a surprisingly calm region of gas within the turbulent center of the Milky Way, offering new clues about how stars begin to form even in extreme environments. This finding suggests that the first steps of star birth may unfold in similar ways across very different regions of our galaxy.

Using the ALMA Exploration Survey (ACES), researchers mapped gas in the galaxy's Central Molecular Zone-a dense, turbulent region where gas typically moves faster than the speed of sound. Within this harsh environment, the team identified a small "subsonic" pocket where gas moves more slowly and smoothly, creating conditions favorable for star formation. Detailed observations revealed a filament-like structure within this calm zone, where gas motions are gentle and gravity is strong enough to hold material together-key ingredients for forming new stars. This transition from chaotic to calm gas occurs over remarkably small distances.

Until now, such calm conditions had only been observed in nearby star-forming regions. This new finding shows they can also arise in extreme environments like the Galactic Center, suggesting a universal process. Researchers say the gas that formed our Sun likely passed through a similar calm phase billions of years ago. Future work, including machine learning analysis of vast datasets, aims to uncover more of these hidden "islands of calm."

The discovery was presented by Rojita Buddhacharya of the Center for Astrophysics | Harvard & Smithsonian and Liverpool John Moores University at the 248th American Astronomical Association meeting, featured in a press conference on Tuesday, June 16th at 10:15am PDT. Find a recording from this presentation on the AAS Press Office YouTube channel.

This text was adapted from a press release shared by the Center for Astrophysics | Harvard & Smithsonian. Read their full press release here.

About ALMA

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

About NRAO

The National Radio Astronomy Observatory (NRAO) is a major facility of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

This news article was originally published on the NRAO website on June 16, 2026.