"By illuminating gas along our line of sight, the quasar gives us extensive information about the composition and state of the gas," explained Anna-Christina Eilers of MIT in Cambridge, Massachusetts, the lead author of another team paper. (Find it at the center of this view: It is tiny and pink with six prominent diffraction spikes.) Scientists aimed Webb in the direction of a quasar-an extremely luminous active supermassive black hole that acts like an enormous flashlight-highlighting the gas between the quasar and our telescopes. Lilly's team intentionally targeted a time just before the end of the Era of Reionization, when the universe was not quite clear and not quite opaque-it contained a patchwork of gas in various states. Over the next hundred million years, these transparent "bubbles" continued to grow larger and larger, eventually merging and causing the entire universe to become transparent. Webb's data shows that these relatively tiny galaxies drove reionization, clearing massive regions of space around them. These regions of transparent gas are gigantic compared to the galaxies-imagine a hot air balloon with a pea suspended inside. "With Webb's data, we are seeing galaxies reionize the gas around them." "Not only does Webb clearly show that these transparent regions are found around galaxies, we've also measured how large they are," explained Daichi Kashino of Nagoya University in Japan, the lead author of the team's first paper. The new results effectively pull back the curtain at the end of this reionization period. Researchers have long sought definitive evidence to explain these transformations. Then, the universe hit "repeat." The gas again became hot and ionized-likely due to the formation of early stars in galaxies, and over millions of years, became transparent. Over hundreds of millions of years, the gas cooled. After the big bang, gas in the universe was incredibly hot and dense. The results, from a research team led by Simon Lilly of ETH Zürich in Switzerland, are the newest insights about a time period known as the Era of Reionization, when the universe underwent dramatic changes. Why? New data from NASA's James Webb Space Telescope has pinpointed the reason: The galaxies' stars emitted enough light to heat and ionize the gas around them, clearing our collective view over hundreds of millions of years. But 1 billion years after the big bang, the gas had become completely transparent. In the early universe, the gas between stars and galaxies was opaque-energetic starlight could not penetrate it. Credit: NASA, ESA, CSA, Simon Lilly (ETH Zürich), Daichi Kashino (Nagoya University), Jorryt Matthee (ETH Zürich), Christina Eilers (MIT), Rob Simcoe (MIT), Rongmon Bordoloi (NCSU), Ruari Mackenzie (ETH Zürich) Image Processing: Alyssa Pagan (STScI) Ruari Macken Over the next hundred million years, the bubbles grew larger and larger, eventually merging and causing the entire universe to become transparent. They also used Webb to precisely measure the gas around the galaxies, identifying that “bubbles” of ionized gas have a 2 million light-year radius around the tiny galaxies.
By analyzing new observations from NASA's James Webb Space Telescope, a team led by Simon Lilly of ETH Zürich in Switzerland found evidence that galaxies that existed 900 million years after the big bang ionized the gas around them, causing it to become transparent.
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