\"Misty Moons\": a lensed galaxy from cosmic dawn
· BehindLines newsroom
Astronomers describe a galaxy nicknamed "Misty Moons" that existed less than 500 million years after the Big Bang. According to Phys.org, the study, led by Minami Nakane of the University of Tokyo, appears in The Astrophysical Journal. The corresponding text can also be read on arXiv, which lists several versions since November 2025.
Magnification from a galaxy cluster
The object is observed behind the cluster MACS J0257.1-2325. According to arXiv, the cluster's mass bends and amplifies the light from the galaxy, whose image appears several times over: two independent lens models propose five multiple images. Phys.org says the two brightest images are roughly 20 to 30 times brighter than they would be without this effect.
The data come mainly from the NIRCam camera of the James Webb Space Telescope, in 10 filters, supplemented by older Hubble images, according to Phys.org. The galaxy was spotted in the VENUS observing program, and its redshift, denoted z, lies between 11 and 12.
Concentrated clusters of young stars
According to Phys.org, the analysis distinguishes several "clumps": four in one component, three in the other. Each would hold about 10 million solar masses of young, dust-poor stars, possibly proto-globular clusters. According to the authors cited by arXiv and Phys.org, these clumps could account for at least 80% of the galaxy's stellar mass, which suggests star formation concentrated in small, compact regions.
Phys.org reports a star formation density 100 to 10,000 times higher than in nearby dwarf galaxies, which the authors attribute to intense, bursty activity. The central regions are bright enough that a growing supermassive black hole cannot be ruled out as the source of part of the light.
What this means for research
According to arXiv, the authors judge that the galaxy's surface-brightness profile, once the distortion is corrected, resembles that of other faint galaxies observed at z above 10. They present it as an ideal laboratory for exploring the early stages of galaxy formation, whose internal structures are resolved thanks to the lensing effect.
One caveat is in order. These conclusions rest on lens models and on estimates of mass and luminosity, which carry uncertainties. The text has been through several revisions since the first version of November 2025. The authors themselves note that a contribution from a growing black hole cannot be excluded, which could skew part of the interpretation in terms of star formation.