James Webb Space Telescope observes surprising galaxy

March 29, 2025 Tabish Faraz

NASA’s James Webb Space Telescope (JWST) has made a groundbreaking discovery, observing a distant and surprising galaxy that appears to challenge existing models of the early universe.

The galaxy, identified as JADES-GS-z13-1, existed just 330 million years after the Big Bang and was observed emitting ultraviolet light despite the expectation that neutral hydrogen in the early universe would have absorbed such radiation.

This discovery, announced by NASA, places the galaxy within the “era of reionization,” a crucial period in cosmic history when neutral hydrogen atoms were gradually ionized by ultraviolet light from forming stars.

During this epoch, which spanned several hundred million years, the universe transitioned from a dark, opaque state to one that allowed light to travel freely. However, at 330 million years post-Big Bang, sufficient neutral hydrogen should have remained to obscure such a galaxy from Webb’s view, making its detection particularly surprising.

One explanation for this anomaly is that the process of reionization may have started earlier than previously thought, driven by unexpectedly powerful sources of ionizing radiation. These could include the universe’s first generation of stars, known as Population III stars, which are theorized to have been massive, luminous and composed almost entirely of hydrogen and helium.

The JWST, an infrared telescope, detected this galaxy’s ultraviolet emissions because of the phenomenon known as redshift. As light travels through the expanding universe, its wavelength is stretched toward the red end of the spectrum, making originally ultraviolet emissions detectable in the infrared range.

Here is the galaxy’s image released by NASA

Webb's image of the surprising galaxy JADES-GS-z13-1 — A two panel image. At left, hundreds of tiny galaxies are scattered across the black background of space. A small portion of the sky near the bottom is outlined with a white box. Lines extend from the corners of the box to the right panel. At right, a small red dot at the middle is highlighted with white lines and labeled redshift z = 13. At upper left, a face-on spiral galaxy is labeled z = 0.63. At lower right, an edge-on spiral galaxy is labeled z = 0.70. A handful of other small background galaxies are seen against the black background of space. At lower right, the panel is labeled JADES-GS-z-13-1. Credit: NASA, ESA, CSA, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA), Joris Witstok (Cambridge, University of Copenhagen), P. Jakobsen (University of Copenhagen), Alyssa Pagan (STScI), Mahdi Zamani (ESA/Webb), JADES Collaboration

This observation raises new questions about the timeline and mechanisms of cosmic reionization. Scientists will continue studying similar galaxies to refine their understanding of the early universe’s evolution. The findings from Webb’s latest observations are expected to reshape current astrophysical theories and deepen humanity’s knowledge of the cosmos.

Featured image is cropped, while its version displayed in article body is not. Image license: CC BY 2.0