Hugely exciting: Oldest galaxies in the universe found
18 Agosto, 2018, 10:38 | Author: Enrique Watson
It took thousands of years for that to change, and the first atoms of hydrogen formed about 380,000 years after the Big Bang.
A group of researchers has been studying the galaxies that are orbiting our own Milky Way galaxy. Once gathered inside the haloes, the vast clouds of hydrogen gradually became unstable and collapsed to form the first stars, and subsequently, the first galaxies. This period is sometimes called the Cosmic Dark Ages because there were no stars or other objects producing light or other frequencies in the electromagnetic spectrum.
Galaxy creation stalled for roughly a billion years as the ionized hydrogen atoms cooled back down to the point where they could settle into larger dark matter haloes, and be used up in the creation of further stars and galaxies. These were hydrogen atoms, the simplest element in the periodic table. It would take nearly 100 million years longer for the universe to cool enough that the atoms could clump together to form stars that populated the very first galaxies.
The first was a very faint population consisting of the galaxies that formed during the "cosmic dark ages". This, in turn, shielded ionized gas from radiation, allowing it to cool and form stars.
Remarkably, the team found that a model of galaxy formation that they had developed previously agreed perfectly with the data, allowing them to infer the formation times of the satellite galaxies.
Scientists at the Instituto de Astrofísica de Canarias (IAC) in Spain believe that it might have formed about 300 million years after the "Big Bang".
IAC researcher Jonay González Hernández said: 'Theory predicts that these stars could form just after, and using material from, the first supernovae, whose progenitors were the first massive stars in the Galaxy'.
This distribution of older and younger galaxies are in line with the Lambda-cold-dark-matter model.
IAC director Rafael Rebolo said: 'Detecting lithium gives us crucial information related to Big Bang nucleosynthesis.
The intense ultraviolet radiation emitted by the first galaxies destroyed the remaining hydrogen atoms by ionising them - knocking out their electrons - making it hard for this gas to cool and form new stars.
The image below shows the distribution of satellite galaxies orbiting a computer-simulated galaxy, as predicted by the Lambda-cold-dark-matter cosmological model. Eventually, the halos of dark matter became so massive that even ionized gas was able to cool.
Dr. Sownak Bose, who was a Ph.D. student at the ICC when this work began and is now a research fellow at the Harvard-Smithsonian Center for Astrophysics, said: "A nice aspect of this work is that it highlights the complementarity between the predictions of a theoretical model and real data".
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