Galaxy Lit Up Just 330 Million Years After the Big Bang express
Light from a distant galaxy traveled to us for 13.4 billion years. The James Webb Space Telescope caught it and split it into colors. The spectrum shows a bright hydrogen line, like a fingerprint saying that galaxy GS-z13-1-LA is actively forming stars.
Young hot stars inside the galaxy act like floodlights. They emit ultraviolet rays that strip electrons from surrounding hydrogen atoms. This creates a transparent bubble around the galaxy — a region where the neutral hydrogen fog has already cleared. According to calculations, the bubble is about 0.2 megaparsecs across (roughly 650,000 light-years).
Near GS-z13-1-LA, astronomers spotted 16 more candidate galaxies. Together, they might create an even larger bubble. If so, the galaxy would need less effort, but its "floodlight" still works at the edge of what's possible. This is an important sign: just 330 million years after the big bang, the first galaxies began clearing the universe of fog. Thus ended the dark ages — the era when space was opaque to ultraviolet light.
The James Webb Space Telescope looks into the past like a time machine. Each such distant object is a window into the era when the first lights turned on. GS-z13-1-LA is one of the earliest beacons we've been able to make out.
Original abstract
as written by the authors arXiv:2603.18775
$$\require{mediawiki-texvc}$$Galaxy assembly was already well underway in the first 400 Myr of cosmic time, as recently revealed by JWST. However, the contribution of these early galaxies to cosmic reionisation remains uncertain. Here we present new JWST/NIRSpec observations of GS-z13-1-LA obtained as part of the OASIS and JADES programmes, whose combined deep (56 h) NIRSpec/PRISM spectrum confirms the Lyman-$$\mathrm{\alpha}$$ line detection and blue UV continuum at redshift $$z = 13.1$$ presented in a previous work. The measured Lyman-$$\mathrm{\alpha}$$ emission (rest-frame equivalent width of $$66_{-9}^{+10}\,\AA$$) and steep continuum slope ($$\beta_\text{UV} \approx -3$$) point towards GS-z13-1-LA hosting a remarkably hot and powerful ionising source, and allow at most a modest contribution from the nebular continuum. The steep turnover of the continuum is still present, but less pronounced in the new OASIS spectrum. Combined, this implies that ionising photons may escape GS-z13-1-LA at a sufficient rate to weaken the other, still undetected UV lines, and to lead the formation of a small ionised bubble ($$R_\text{ion} \approx 0.2\,\mathrm{pMpc}$$). A yet larger bubble could alleviate the required ionising production efficiency of GS-z13-1-LA from $$\xi_\mathrm{{ion}} \approx 10^{26.4}\,\mathrm{{Hz\,erg^{{-1}}}}$$ down to $$\approx 10^{25.9}\,\mathrm{{Hz\,erg^{{-1}}}}$$, still extremely high but more readily reconcilable with stellar models. In turn, this would require a notable overdensity of galaxies with highly efficient ionising capabilities, a scenario for which tentative evidence is found in the form of 16 nearby photometric candidates and one spectroscopically confirmed source, JADES-GS-z13-0. The new OASIS observations therefore confirm the overall picture of GS-z13-1-LA as an early beacon of reionisation, providing compelling evidence for its start only 330 Myr after the Big Bang.
Light from galaxy GS-z13-1-LA traveled to us for 13.4 billion years — almost the entire age of the universe. When that light set off, Earth didn't exist yet.
In the series Star Trek, ships explore nebulae where gas is ionized by starlight. A similar process, but on the scale of the entire early universe, is described in this work.