Astronomers have just unveiled a breathtaking new view of the very center of our galaxy, the Milky Way. Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile’s Atacama Desert, they stitched together the largest ALMA image ever produced, a mosaic spanning an area in the sky as wide as three full Moons side by side.
What it reveals is nothing short of extraordinary: a tangled web of cold gas filaments, the raw material from which stars are born, swirling around the supermassive black hole at the galaxy’s core.
“It’s a place of extremes, invisible to our eyes, but now revealed in extraordinary detail,” says Ashley Barnes, astronomer at the European Southern Observatory (ESO) in Germany.
This montage shows the distribution of different molecules in the Central Molecular Zone (CMZ) of the Milky Way. The observations were made with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the ALMA CMZ Exploration Survey (ACES). ACES has mapped the distribution of several dozen molecules at the center of our galaxy. Five of these molecules are shown here, from top to bottom: carbon monosulfide, isocyanic acid, silicon monoxide, sulfur monoxide, and cyanoacetylene. Credit: ALMA (ESO/NAOJ/NRAO) / S. Longmore et al.
The region, known as the Central Molecular Zone (CMZ), spans more than 650 light-years. It’s a chaotic environment packed with dense clouds of gas and dust, and it’s the only galactic nucleus close enough to Earth for us to study in such fine detail. The dataset reveals structures ranging from vast filaments dozens of light-years long down to tiny gas clouds surrounding individual stars.
The survey, called ACES (ALMA CMZ Exploration Survey), focuses on cold molecular gas. This gas contains dozens of molecules such as simple silicon monoxide, complex organics such as methanol, acetone, and ethanol, etc. These molecules flow along filaments, feeding clumps of matter where stars can ignite.
The CMZ is home to some of the most massive stars in the Milky Way.
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 different molecules are displayed in different colours. The entire image – the largest ever made with ALMA – is as long as three full Moons side-by-side in the sky.
Credit:
ALMA(ESO/NAOJ/NRAO)/S. Longmore et al. Stars in inset: ESO/D. Minniti et al. Milky Way: ESO/S. Guisard
“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,” explains Steve Longmore, ACES leader and professor of astrophysics at Liverpool John Moores University, UK.
By studying star birth in this extreme environment, astronomers hope to test whether our theories of star formation hold under such chaotic conditions.
“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.”
The team anticipated detail, but the final image exceeded expectations. “We anticipated a high level of detail when designing the survey, but we were genuinely surprised by the complexity and richness revealed in the final mosaic,” says Katharina Immer, ALMA astronomer at ESO.
And this is only the beginning. “The upcoming ALMA Wideband Sensitivity Upgrade, along with ESO’s Extremely Large Telescope, will soon allow us to push even deeper into this region, resolving finer structures, tracing more complex chemistry, and exploring the interplay between stars, gas, and black holes with unprecedented clarity,” says Barnes.
This new image of the Milky Way’s center isn’t just a pretty picture; it’s like looking back in time. By studying the Central Molecular Zone (CMZ), scientists can learn how galaxies like ours grew in their early days, when stars formed quickly and under very extreme conditions.
It’s a reminder that even in the most hidden corners of the universe, stories are waiting to be told, stories written in gas, dust, and starlight, now revealed in dazzling detail.
This research was presented in a series of papers presenting the ACES data, to appear in Monthly Notices of the Royal Astronomical Society:
Paper I – ALMA Central Molecular Zone Exploration Survey (ACES) I: Overview paper https://arxiv.org/abs/2602.20340
Paper II – ALMA Central Molecular Zone Exploration Survey (ACES) II: 3mm continuum images https://arxiv.org/abs/2602.20240
Paper III – ALMA Central Molecular Zone Exploration Survey (ACES) III: Molecular line data reduction and HNCO & HCO+ data https://arxiv.org/abs/2602.20276
Paper IV – ALMA Central Molecular Zone Exploration Survey (ACES) IV: Data of the two intermediate-width spectral windows https://arxiv.org/abs/2602.20445
Paper V – ALMA Central Molecular Zone Exploration Survey (ACES) V: CS(2-1), SO 2_3-1_2, CH3CHO 5_(1,4)-4_(1,3), HC3N(11-10) and H40A lines data
Paper VI – ALMA Central Molecular Zone Exploration Survey (ACES) VI: ALMA Large Program Reveals a Highly Filamentary Central Molecular Zone (undergoing minor revision) https://arxiv.org/abs/2602.20262