There are still many hidden mysteries regarding the universe (among them, what is dark matter and its origin); But some data does seem lucid enough for scientists, who have spent decades scrutinizing the visible sky and analyzing the clues that ancient galaxies, and the stars that make them up, leave us through powerful telescopes, and the observation of data such as radiation microwave background.
One of the things that scientists are clear about is the age of the universe: it is estimated that 13.7 billion years ago is the date of the origin of time. Therefore, it is exciting to discover new celestial structures that confirm this conception. Every new discovery that is close to the estimated age of the universe excites astronomers. The latest finding has been made by a team of cosmologists from Durham University and the Harvard-Smithsonian Center for Astrophysics: they have found evidence that the fainter satellite galaxies orbiting our own Milky Way are among the first galaxies to form. in our universe.
Scientists working on this research have described the find as “enormously exciting”, explaining that finding some of the first galaxies in the universe in orbit around the Milky Way is “equivalent to finding the remains of the first humans that inhabited the Earth” .
Specifically, the galaxies Segue-1, Bootes I, Tucana II, and Ursa Major I are some of the earliest galaxies formed that are believed to be more than 13 billion years old.
380,000 years after the Big Bang the first atoms were formed. These were hydrogen atoms, the simplest element on the periodic table. These atoms accumulated in the nebulae and gradually began to cool down to settle into the small clumps or “halos” of dark matter that emerged from the Big Bang.
With the formation of the first galaxies, light was made in the universe, bringing the cosmic Dark Age, a cooling phase, known to last approximately 100 million years, to an end. So the gas that had cooled within the nebulae became unstable and began to form stars: these objects are the first galaxies to form.
Video: Some of the oldest galaxies in the universe orbit our Milky Way
Dr. Sownak Bose of the Harvard-Smithsonian Center for Astrophysics, working with Dr. Alis Deason and Professor Carlos Frenk at the Durham University ICC, identified two populations of satellite galaxies orbiting the Milky Way.
The first was a very weak population consisting of galaxies that formed during the “Cosmic Dark Age”, when there was still no star trail. The second was a slightly brighter population consisting of galaxies that formed hundreds of millions of years later, once hydrogen that had been ionized by the intense ultraviolet radiation emitted by the first stars was able to cool down into more massive dark matter halos. .
As detailed on Phys.org , the team discovered, to their surprise, that a galaxy formation model they had previously developed matched the data perfectly, allowing them to deduce the age of satellite galaxies.
According to Professor Carlos Frenk, Director of the Institute of Computational Cosmology at Durham University: “Finding some of the first galaxies that formed in our Universe orbiting in the backyard of the Milky Way is the astronomical equivalent of finding the remains of the first humans to inhabit the Earth. It’s very exciting. “
Reference: The imprint of cosmic reionisation on the luminosity function of galaxies, S. Bose et al, The Astrophysical Journal, DOI: doi.org/10.3847/1538-4357/aacbc4
