There was a time when our entire universe was shrouded in thick fog. Then the veil lifted. Thanks to the stars that shone in the heart of the first galaxies, data from the James Webb Space Telescope show today.
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First there was the Big Bang. And in those early moments, our universe bore little resemblance to what we know today. It was filled with an incredibly dense and hot gas. A gas that took hundreds of millions of years to cool. It was then completely opaque. Then, as if “someone” had pressed the “repeat” button, the gas began to warm up again. He ionized. And it finally became transparent.
For a long time, researchers wondered who that “someone” might be who hit the “repeat” button. Now, new data from the James Webb Space Telescope (JWST) sheds light on this mysterious period, which astronomers call the Reionization Epoch.
To track down the culprit, researchers at the Swiss Federal Institute of Technology Zurich (ETH, Switzerland) have targeted a moment in the life of the universe that is nearing the end of this era of reionization. A moment when he wasn’t quite transparent yet, but also not quite opaque anymore. By aiming the JWST at a distant quasar, they obtained information about the gas that lies between us and this active supermassive black hole, so bright it appears like a giant flashlight. Its light was sometimes absorbed by an opaque gas, sometimes transmitted by a transparent gas. And so the researchers got detailed information about the composition and the state of the gas.
An incredible quasar that sheds light on the darkness
As a second step, the astronomers again relied on the James Webb Space Telescope to identify galaxies near their line of sight. And they were not disappointed. Where they had hoped to find a few dozen, they ended up with almost 120! Galaxies that were restless and actively forming stars. And mostly surrounded by transparent regions about 2 million light-years in radius — about the distance that separates our Milky Way from the nearest galaxy, Andromeda. Like they literally cleared the space around them at the end of the Reionization Epoch.
Thus, the first relatively small galaxies in the universe, and the stars they contained, appear to have been the ones that, by emitting amounts of light and heat, hit the “repeat button” to induce reionization, creating transparent “bubbles” around them created around. Bubbles that continued to expand over the next million years until they merged, making our universe completely transparent. A scenario that astronomers hope to soon confirm by examining five other regions, each illuminated by a different quasar.
In the meantime, however, the ETH team points to a different result obtained using JWST data. Confirming the colossal mass of the quasar allowed them to reach these conclusions. The object would weigh no less than 10 billion times more than our sun. This makes it the most massive black hole known in the early Universe. Another riddle. Because astronomers have not yet been able to explain how quasars got so large so early in our history.