The cosmic dawn ended 200 million years later than cosmologists thought


Artist’s impression of a bright quasar – IgorZh /

Using light from dozens of distant quasars, the astronomers determined that the cosmic dawn, during which the first stars began to form, ended much later than expected.

67 quasars analyzed

Over a period of approximately 100 million years, starting approximately 380,000 years after the big Bang, the cosmos was largely shrouded in darkness. Then, stars and galaxies began to form, emitting light and ionizing intergalactic hydrogen gas in a process called reionization, or cosmic dawn.

In the context of the work published in the journal Royal Astronomical Society Monthly Notices, Sara Bossmann and his colleagues from theMax Planck Institute they were able to more accurately determine when this phase was over, based on the light emitted by 67 quasars, extremely bright objects powered by supermassive black holes. Turning out far enough for scientists to be sure they had formed in the billion years since big Bangthese were observed using the Very large telescope to Chile and the Observatory WM Keck to Hawaii.

When the light from the quasars traveled to the Land, different wavelengths have been absorbed by hydrogen in its ionized and non-ionized forms. Taking into account the constant expansion of theUniverseGerman scientists analyzed dark absorption lines in the light spectrum to determine when it stopped passing through syndicated hydrogen and started encountering only ionized hydrogen in intergalactic space.

Deep Space Galaxy – Outer Space /

A phase that ended 1.1 billion years after the Big Bang

During reionization, galaxies emit gigantic bubble-like structures “, To explain bosman. ” It is generally believed that such a process ends when the latter merge and the hydrogen is ionized uniformly around all quasars.. “

This approach allowed the team to determine that the cosmic dawn ended 1.1 billion years after big Bang, 200 million years later than predicted by previous models. This implies that the first generation of stars and galaxies, at the origin of the reionization, are closer and therefore easier to observe than cosmologists thought.

Since the Big Bang, the Universe has gone through many phases, which we are only beginning to trace “, valued bosman. “ The next step will be to go even further into the past and link the reionization data to the galaxies behind the process, so you can really see the gas-destroying galaxies.. “


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