Central Molecular Zone (CMZ) of The Milky Way | ALMA
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). The European Southern Observatory 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 image shows the location of the Central Molecular Zone (CMZ), a region at the core of our galaxy rich in dense and intricate gas clouds. This zone has been mapped with the Atacama Large Millimeter/submillimeter Array (ALMA), as part of the ALMA CMZ Exploration Survey or ACES. The inset is an ACES image where molecules are displayed in a variety of colors. The entire image – the largest ever made with ALMA—is as long as three full Moons side-by-side in the sky.
A wispy cosmic cloud against a dark starry background. The cloud is horizontally elongated. It has an overall pinkish shade, but it is full of intricate filaments in distinct colors.
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). The European Southern Observatory 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 molecule types, five are shown here: 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 Visible and Infrared Survey Telescope for Astronomy (VISTA) telescope as part of another 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 sharper because the ALMA observations do not cover the entire rectangular area here.
Cold molecular gas flows along filaments feeding into clumps of matter that stars can grow from. In the outskirts of the Milky Way we know how this process happens, but within the central region the events are much more extreme. “The CMZ hosts some of the most massive stars known in our galaxy, many of which live fast and die young, ending their lives in powerful supernova explosions, and even hypernovae,” says ACES leader Steve Longmore, a professor of astrophysics at Liverpool John Moores University, UK. With ACES, astronomers hope to better understand how these phenomena influence the birth of stars and whether our theories of star formation hold in extreme environments.
“By studying how stars are born in the CMZ, we can also gain a clearer picture of how galaxies grew and evolved,” Longmore adds. “We believe the region shares many features with galaxies in the early Universe, where stars were forming in chaotic, extreme environments.”
Credit: ALMA(ESO/NAOJ/NRAO)/S. Longmore et al. Background: ESO/D. Minniti et al.
Release Date: Feb. 25, 2026
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