“At this period, light starts coming into the universe because of new stars and galaxies, but it wasn't known what was really the first source of reionization of the universe,” Bacon said. Reionization was sparked when the first stars and galaxies burst into existence, illuminating the galaxy with energetic ionizing light and ending the so-called cosmic “dark ages.” It was the birth of the universe as we know it today, complete with dazzling galaxies filled with a variety of different star types. “I find this very interesting because there's numerous consequences of this population of tiny star-forming galaxies,” Bacon said.įor instance, he continued, if these galaxies are already abundant one billion years after the Big Bang, it suggests that they might be the driver of an epic earlier period known as the epoch of reionization, which occurred when the universe was a few hundred million years old. What’s more, the study’s discovery of such a large population of dwarf galaxies in the early universe could shed light on some of the biggest mysteries about this ancient era, including how the first stars and galaxies formed and lit up the cosmos with their brilliance. In other words, to bring back the streetlight analogy, Bacon and colleagues have found a way to look for missing keys far from the glare of city lights.ĭetecting the elusive glow of the filaments, without the help of radiant cosmic lanterns, presented an enormous challenge that required years of careful planning and many failed previous attempts to image the cosmic web in the gloomy stretches of intergalactic space. While quasar-adjacent observations are very important, the new study is a big step forward because it demonstrates “the first detection ever” of the cosmic web “in the normal region of the intergalactic medium,” Bacon added. They do not really represent where most galaxies form.” They are in what we call the nodes, where the filaments cross, and these are very dense regions. “But the point is that these quasars are located in a specific place of the cosmic web. “We can indeed see, because of the light of the quasars, the first clue that the cosmic web is there,” he said. While these observations provide important clues about the structure of the universe, Bacon said they are an example of the “streetlight effect,” an anecdote about observational bias in which a person searches for their missing keys at night only under streetlights, simply because that’s where the ground is visible. Scientists have previously captured glimpses of these filaments close to quasars, which are extremely bright galactic cores.
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