The oldest galaxies in the universe discovered
Galaxy By Louis Spencer JR | September 6, 2018
The international team of astronomers has found evidence that weak satellite galaxies revolving around the Milky Way are among the very first galaxies born in the universe and their age exceeds 13 billion years.
When the universe was about 380 000 years old, the very first atoms were formed. These were the atoms of hydrogen, the simplest element in the periodic table. They gathered in the clouds and began to gradually cool down and settle in small clusters or halos of dark matter that arose from the Big Bang.
This is a perfect example of how observations of the smallest dwarf galaxies living near the Milky Way can be used to study the early universe.
-Dr. Alice Dyson, research fellow at the University of Durham, UK
This cooling phase, known as the dark ages, lasted about 100 million years. Eventually, the gas that cooled inside the halos became unstable and began to form stars. With the formation of the first galaxies, the universe shone, turning the page of dark ages.
In their work, astronomers describe two populations of satellite galaxies revolving around the Milky Way. The first consists of galaxies formed during the cosmic dark ages. The second, slightly brighter population includes galaxies that formed hundreds of millions of years later, when hydrogen, ionized by the intense ultraviolet radiation of the first stars, cooled in a more massive halo.
It is remarkable that our discovery and the following conclusions support the current model of the universe [Lambda-Cold Dark Matter], in which the elementary particles that make up dark matter control cosmic evolution.
-Carlos Frenk, co-author of the study at the University of Durham
Subsequently, intense ultraviolet destroyed the remaining hydrogen atoms, ionizing them (knocking out electrons), which made it difficult to cool the gas and form new stars. The process of formation of galaxies has stopped for several billion years. But in the end the halos of dark matter became so massive that even ionized gas could cool down. The birth of the stars resumed, which led to the appearance of bright galaxies, such as our Milky Way.