Illustration showing the reionization of the Universe. Following the Big Bang, the Universe was little more than a soup of charged subatomic particles

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Illustration showing the reionization of the Universe. Following the Big Bang, the Universe was little more than a soup of charged subatomic particles and energy (top, red). As the Universe expanded and cooled, there came a point – at an age of 300, 000 years – when most of the protons and electrons had combined to form a sea of neutral hydrogen gas. This heralded the so-called Dark Ages, when the Universe became opaque. A few hundred million years later, some of the hydrogen had started to gather into stars and, in turn, galaxies and quasars. These new structures unleashed a torrent of ionizing radiation that began to ionize the remaining neutral hydrogen, beginning the so-called Epoch of Reionization. At an age of 1 billion years, the Universe became transparent again (bottom).

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Size: 4543px × 5843px
Photo credit: © MARK GARLICK/SCIENCE PHOTO LIBRARY / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: ages, art, artwork, bang, big, cosmology, cosmos, dark, early, formation, galaxies, hydrogen, illustration, ionised, ionized, neutral, quasars, reionisation, reionization, stars, universe