Free Astronomy Magazine May-June 2026

14 MAY-JUNE 2026 ASTRO PUBLISHING time the cold gas across this whole region has been explored in such de- tail. The region featured in the new image spans more than 650 light- years. It harbours dense clouds of gas and dust, surrounding the super- massive black hole at the centre of our galaxy. “It is the only galactic nucleus close enough to Earth for us to study in such fine detail,” says Barnes. The dataset reveals the CMZ like never before, from gas structures dozens of light-years across all the way down to small gas clouds around individual stars. The gas that ACES — the ALMA CMZ Exploration Survey — specifically ex- plores is cold molecular gas. The survey unpacks the intricate chemistry of the CMZ, detecting doz- ens of different mole- cules, from simple ones such as silicon monoxide to more complex organic ones like methanol, ace- tone or ethanol. Cold molecular gas flows along filaments feeding into clumps of matter out of which stars can grow. 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 hy- pernovae,” says ACES leader Steve Longmore, a professor of astrophysics at Liverpool John Moores University, UK. With ACES, astronomers hope to better under- stand how these phe- nomena influence the birth of stars and wheth- er our theories of star for- mation hold in extreme environments. “By study- ing 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.” To collect this new da- taset, astronomers used ALMA, which is operated by ESO and partners in Chile’s Atacama Desert. In fact, this is the first time such a large area has been scanned with this facility, making this the largest ALMA image ever. Seen in the sky, the mo- saic — obtained by stitch- ing together many in- dividual observations like putting puzzle pieces to- gether — is as long as three full Moons side-by- side. “We anticipated a high level of detail when designing the survey, but we were genuinely sur- prised by the complexity and richness revealed in the final mosaic,” says Katharina Immer, an ALMA astronomer at ESO who is also part of the project. T his montage shows the distribution of different molecules in the Central Molecular Zone (CMZ) of the Milky Way. The ob- servations were made with the Atacama Large Millimeter/sub- millimeter Array (ALMA), as part of the ALMA CMZ Exploration Survey or ACES. ACES has mapped the distribution of several dozen molecules at the centre of our galaxy. Here we show five of them, from top to bottom: carbon monosulphide, isocyanic acid, silicon monoxide, sulphur monoxide, and cyanoacetylene. [ALMA(ESO/NAOJ/NRAO)/S. Longmore et al.] !