A Galaxy That Slept for Half a Billion Years ⚡ экспресс
Using medium-band filters of the NIRCam camera on the James Webb Space Telescope, galaxy CANUCS-A370-2228423 (z=5.95, log M*/M☉ = 9.14), nicknamed 'Hibernating', has been discovered. Its star formation history shows rapid growth in the first 300 million years after the Big Bang (z > 14) forming a progenitor with stellar mass log M*/M☉ = 8.7, comparable to the few spectroscopically confirmed galaxies at those redshifts. This is followed by several hundred million years of suppressed star formation, resulting in an exceptionally strong Balmer break, exceeding that of all known galaxies in the first billion years by a factor of about 3. Systems like 'Hibernating' turn out to be overabundant in the observed volume compared to cosmological simulations (probability of finding one < 0.2%). This result challenges the scenario in which all bright early-universe galaxies grow into massive objects, and points to an alternative path: after an early burst, such galaxies may fade, becoming inefficient dwarfs, indicating greater diversity in the initial stages of evolution.
The James Webb Space Telescope looked back to a time when the universe, just after the Big Bang, was only a billion years old, and found the 'Sleepy' galaxy. Unlike its neighbors, which shone with young stars, it looked tired and dim.
Splitting light into its colors, scientists realized: in its first 300 million years, Sleepy blazed to life, piling up a mountain of stars, and then fell asleep for half a billion years. This slumber left a mark—a hydrogen dip in the glow, a sharp cutoff in the spectrum. It turned out to be three times stronger than in any other galaxy of that era, like the echo of a suddenly cut-off scream.
The discovery flips the script. Previously, it was thought that bright early galaxies inevitably grow into giants. Sleepy, instead, became a dim dwarf—and perhaps the majority of these 'expectation-defying' sleeping beauties exist.
🎯 By today, Sleepy would have become so dim that no modern telescope could see it—half a billion years of slumber have made it nearly invisible.