The Big Bang captures the imagination like no other theory in science – the magnificent birth of our universe. But did you know what happened next?
It was 100 million years of darkness. When the first stars finally lit up in space, they were bigger and brighter than all subsequent ones. They shone so intensely with ultraviolet light that they turned the surrounding atoms into ions. The cosmic dawn – from the first star to the end of the reionization era – lasted about one billion years.
Where did the first stars come from? And how are they going to the galaxies that we see today? These are our main questions.
-Professor Michael Norman, director of the Supercomputer Center in San Diego (USA), author of a new review published in the journal Frontiers in Astronomy and Space Sciences
Researchers such as Professor Michael Norman solve mathematical equations in the cubic virtual universe. They spent more than 20 years using and improving software to better understand the Cosmic Dawn.
To begin with, a code was created that allowed us to model the formation of the first stars in the Universe, describing their movement and chemical reactions inside gas clouds and the huge gravitational pull of a much larger, but invisible mass of mysterious dark matter.
Clouds of pure hydrogen and helium collapsed under their own force of gravity to kindle single stars, hundreds of times more massive than our Sun.
-Michael Norman
The very first heavy elements formed in the nuclei of the first stars: lithium and beryllium grains. But with the death of short-lived giants who exploded into dazzling supernovae, metals such as iron were scattered in abundance into space.
These data were added to the virtual Universe to simulate the enrichment of gas clouds with newly formed metals, which led to the formation of a new type of stars. The transition was fast: over 30 million years, almost all the new stars in them were enriched with metals, despite the fact that the process proceeded locally and in the final simulation more than 80% of the virtual
From stars to galaxies. The formation of metal-free giant stars has not stopped. Small clusters arose where there was enough dark matter cooling the virgin clouds of hydrogen and helium.
New generations of stars were smaller and much more numerous, because chemical reactions became possible with metals. At this stage in the modeling of the Universe, the first objects appear that can rightly be called galaxies, including dark matter, gas and metal-enriched stars.
The size of the first galaxies turned out to be less than expected, since the intense radiation from young massive stars condensed the gas into star-forming regions. In turn, radiation from the smallest galaxies significantly contributed to cosmic reionization.
These difficult-to-determine, but numerous galaxies can explain the period of the end of the Cosmic Dawn, when the reionization was completed.
Michael Norman and his colleagues explain that computational limitations in digital simulations are overcome by simplifying parts of the model that are least relevant for the results of interest. The authors also highlight areas of uncertainty that need to be addressed by new generations of simulations using improved codes on future high-performance computing platforms.
This will help scientists understand the role of magnetic fields, X-rays and cosmic dust in gas cooling, as well as the predominance and behavior of mysterious dark matter that stimulates star formation.
After the big bang
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