Imagine a city where streetlights shine, but their glow isn't scattered by fog — instead, it streams into the sky almost entirely. That's what galaxy U37126 looks like, as seen by astronomers in the early universe with the James Webb Space Telescope. Its light has traveled for more than 13 billion years to reach us.
In typical galaxies, young hot stars are surrounded by lots of gas. This gas glows when heated by the stars, but it also absorbs some of the ultraviolet radiation. In U37126, however, astronomers saw none of the expected gas glow. Instead, the starlight itself was extremely bright and blue. This means the galaxy is almost devoid of a gaseous "fog"—it has been blown out by intense radiation and winds from massive stars.
Such a "bare" galaxy lets more than 86% of its ultraviolet light escape. For comparison, in typical galaxies this fraction is often less than 10%. It was this kind of light that heated and ionized intergalactic hydrogen in the early universe, making space transparent. Even if such galaxies were rare, just a few percent of all galaxies, they could have provided half or even all of the necessary light.
Astronomers built a model of the stellar population of U37126. They found that the galaxy hosts very young and massive stars, with an enormous star formation rate: about 10 solar masses per year. Yet the galaxy itself is tiny, so the density of stars and the rate of star birth per unit area are among the highest known. It seems that gas in the galaxy's center quickly turned into stars, and then powerful radiation swept the remaining gas outward. This is how a "naked" island of stars emerged, its light streaming unimpeded into space.
Light from U37126 has traveled for 13.1 billion years — almost the entire age of the universe. We see this galaxy as it was just 400 million years after the Big Bang.