Mind blown: Oldest galaxies in the universe discovered

Christopher Davidson
August 19, 2018

The discovery belongs to a team of astronomers from Durham University in the United Kingdom and the Harvard-Smithsonian Center for Astrophysics in Cambridge (CfA), U.S., who uncovered that some the faintest satellite galaxies floating around the Milky Way are among the first ones to appear after the Big Bang.

Two clusters of galaxies were identified, both thought to more than 13 billion years old and including Segue-1, Bootes I, Tucana II and Ursa Major I. "It is hugely exciting".

The scientists on the project say that their findings support the current evolutionary model of the universe dubbed the "Lambda-cold-dark-matter model" and in that model elementary particles that make up the dark matter drive the cosmic evolution. These atoms, which gathered into clouds, eventually began to cool and settled into small clumps of dark matter that emerged from the big bang.

Believed to be the first nebula began to form when the universe was about 380,000 years old.

The second was a slightly brighter population consisting of galaxies that formed hundreds of millions of years later, once the hydrogen that had been ionised by the intense ultraviolet radiation emitted by the first stars was able to cool into more massive dark matter halos.

The new study suggests that the first population of dimmer Milky Way satellites are among the oldest galaxies in the universe, which, with the light of their stars, brought an end to the cosmic dark ages. On the other hand, the halos that previously formed from dark matter grew mass to the point that the ionized gas was able to cool, so new galaxies continued forming, resulting in intensively bright galaxies like our own.

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"A decade ago, the faintest galaxies in the vicinity of the Milky Way would have gone under the radar", according to Sownak Bose, a former Ph.D. student at the ICC, now a research fellow at the Harvard-Smithsonian Center for Astrophysics.

Researchers said their discovery aligned perfectly with a model of galaxy formation that they had developed. This destroyed the remaining hydrogen atoms by ionising them (knocking out their electrons), making it hard for this gas to cool and form new stars.

In the study published by Professor Frenk and his team in the Astrophysical Journal, they described how two of the satellite galaxy populations from their discovery could shed some light into the origins of the universe.

A long, long time ago, in a galaxy far, far away.

Our own galaxy, the Milky Way, is one of billions out there in the cosmos. The universe then plunged into its next cosmological phase, dubbed the reionization period, when the larger and brighter galaxies began to take shape - all "culminating in the formation of spectacular bright galaxies like our own Milky Way", sates Dunham University. "Being the first ones, they should have properties that are unique to them", said Frenk. "They were formed at a time when the Universe was much denser, because the Universe was smaller".

With this in mind, the team can continue cherishing their study and working on discovering new galaxies that could hide the answers about the universe formation, and unveil various secrets that we are still not aware of.

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