Cosmic Dawn: The first stars formed 250 to 350 million years after the Big Bang

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The first stars were formed between 250 and 250 million years after the Big Bang and the James Webb space telescope should be able to observe the birth of the very first galaxies directly. This is the result of a research project that has now been presented, in the course of which the age of the stars in the oldest known galaxies and their distance was determined. We see them at a time when the universe was only 550 million years old and the stars in it are between 200 and 300 million years old. When they emerged, they should also have been bright enough that we can soon observe the process and the “cosmic dawn” directly.

The researchers use this poetic term to refer to the so-called reionization epoch in the early universe. During this period, which has now been arranged chronologically, the first stars and galaxies emerged, which in turn supplied the energy with which the hydrogen that had already been formed was reionized, making the universe translucent. The attempt to observe this epoch directly has been considered a kind of Holy Grail in astronomy for decades, the researchers led by Nicolas Laporte from the University of Cambridge now explain. After all, we ourselves consist of the material that is formed in stars and so this experiment is part of the search for our origins.

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Simulation of the formation of the first stars and galaxies (ionizing radiation in yellow)

(Quelle: Dr Harley Katz, Beecroft Fellow, Department of Physics, University of Oxford)

How the team now explains, they analyzed light captured by the Hubble and Spitzer space telescopes from six different galaxies from the early Universe. They show that only 550 million years after the creation of the cosmos. They examined the spectra in relation to a certain hydrogen signature, which can be used to estimate the age of the stars it contains. Co-author Romain Meyer explains that the age of stars in the Milky Way is also determined in the same way. The team has determined that the analyzed galaxies are between 200 and 300 million years old and thus we also have the date of “cosmic dawn”.

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The fact that we can look back so far at all is thanks to the pioneering work of astronomers over the past decade. In the meantime, however, we have reached the limits of the capabilities of the existing space telescopes – which are not getting any younger either. That is why we are now waiting full of excitement for the James Webb space telescope, which is due to be launched this year. The team assumes that the infrared telescope is powerful enough to be able to directly observe the formation of the first galaxies. They have their research work published in the journal Monthly Notices of the Royal Astronomical Society.


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