Cosmic fireworks 12 billion light-years away: a record-breaking survey by IRAM’s 30- meter telescope

Press release Aix-Marseille Université / CNRS

Using the NIKA2 camera on IRAM’s 30-metre telescope, an international team of astronomers, including scientists from the Marseille Astrophysics Laboratory (amU/CNES/CNRS) and the Grenoble Institute of Planetology and Astrophysics (IPAG-OSUG, UGA/CNRS), have achieved a new sensitivity record and discovered a vast cosmic structure comprising massive, dust-rich galaxies dating back to a time when the universe was only one billion years old. The results of this work were published on January 26, 2026, in Astronomy & Astrophysics (A&A).

The NIKA2 Cosmological Legacy Survey (N2CLS), conducted using the NIKA2 millimetre camera on IRAM’s 30-metre telescope, has reached a new milestone in exploring the distant universe. For the first time, a survey has reached the limit of confusion at a wavelength of 1.2 mm with a ground-based instrument, achieving an unprecedented level of sensitivity where residual image blur is caused by indistinguishable distant galaxies rather than instrument noise. This technical achievement ushers in a new era in the mapping of very distant galaxies.

This instrumental milestone has led to the discovery of a record number of massive, dusty, intensely star-forming galaxies located more than 12 billion light-years away. These galaxies are located in the GOODS-North Deep Field, a region of the sky that has been extensively studied by the Hubble Space Telescope (HST), but which has never been observed with such precision in the millimetre range.

Some of these objects are forming stars at a dizzying pace — up to a thousand times faster than our own Milky Way — yet they are completely invisible in the deepest images taken by the HST, as they are completely obscured by dust. Several of these galaxies have now been located through additional observations using the NOEMA interferometer and by cross- referencing infrared data from the James Webb Space Telescope (JWST).

Together, these galaxies are part of an enormous structure that is still forming, an embryonic cluster of galaxies stretching over 30 million light-years, at a time when the universe was only one billion years old. This is the first time such a concentration of dusty, ultra-massive galaxies undergoing intense star formation has been detected at this cosmic epoch. These results suggest that, in certain environments in the early Universe, galaxies can form stars extremely efficiently — far more so than current theoretical models predict.

With gas-to-star conversion efficiencies sometimes exceeding 30%, these galaxies are exhausting their gas reservoirs within just a few tens of millions of years. This initiates a rapid transition to the so-called “quiescent phase”.

This spectacular discovery, the result of a collaboration between ground- and space-based observations, sheds light on phenomena that current models still struggle to reproduce. It also highlights the important role of dense environments in forming large structures in the early Universe. It also emphasises the value of combining IRAM and JWST observations to explore the early stages of large cosmological structure formation.

Reference

Overdense fireworks in GOODS-N: Unveiling a record number of massive dusty star-forming galaxies at z∼5.2 with the N2CLS. G. Lagache et al. Le 26 janvier 2026, Astronomy & Astrophysics.
DOI : 10.1051/0004-6361/20255594

NIKA2 Cosmological Legacy Survey. First measure of the confusion noise at the IRAM 30m Telescope. N. Ponthieu et al. Le 26 janvier 206, Astronomy & Astrophysics.
DOI : 10.1051/0004-6361/202554530

This press release was initially published by CNRS.

Updated on 6 February 2026