Cosmic dawn mapped in 3D reveals a sea of light across the early universe

Astronomers used line-intensity mapping from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) to create a 3D map of the early universe, revealing a vast ‘sea of light’ from hydrogen Lyman-alpha emission that traces galaxy and gas distributions 9–11 billion years ago. The work helps probe gravity and dark energy’s role in cosmic evolution, leveraging hundreds of millions of spectra; further noise-reduction advances will enable mapping even fainter structures and tighten cosmological constraints.