Images from the James Webb Space Telescope have revealed unexpectedly intense light from the first galaxies — colossal star systems that formed shortly after the Big Bang. Imagine a toaster browning a slice of bread in a minute, while an oven takes an hour to bake a loaf — the result is essentially the same. So it is in space: young galaxies poured out powerful light rapidly, like a toaster, rather than building up their stellar populations gradually, like a traditional oven.

The key lies in the stuttering rhythm of star formation. In the early universe, the era right after the Big Bang, gas collapsed into stars not in a steady stream but in short, intense bursts. Yet the fraction of gas turned into stars remained nearly the same as in the modern universe. In other words, the toaster used just as much "dough"—the raw gaseous material, as the oven.

Neither cosmic dust, microscopic solid particles that scatter and absorb light, nor giant solitary stars could alone explain such brilliant glow. Only an accelerated pace of star birth provided the answer. But this wasn't immediately obvious: astronomers modeled various scenarios, comparing them with Webb's data, and only a combination of factors matched the observations. An unexpected twist: supermassive black holes, objects with extreme gravity, located at the centers of galaxies made an additional contribution. As matter fell into them, it heated to colossal temperatures and emitted radiation, making the infant galaxies even brighter.