Physicists Claim That Faintest Galaxies Orbiting Milky Way Are The Oldest In The Universe

A group of researchers has been studying the galaxies that are orbiting our own Milky Way galaxy. According to these researchers, the faintest galaxies that are orbiting the Milky Way are also among the very first galaxies that formed in our universe. The team of researchers includes Professor Carlos Frenk and Dr Alis Deason from the Institute for Computational Cosmology (ICC) at Durham University and Dr Sownak Bose from the Harvard-Smithsonian Center for Astrophysics in America.

The findings of the team of scientists suggest that galaxies including Segue-1, Bootes I, Tucana II, and Ursa Major I are all over 13 billion years old. Our own Milky Way galaxy is estimated to be over 13.51 billion years old (give or take millions of years) while the Universe itself is thought to be around 13.8 billion years old. The scientists say that finding some of the very first galaxies in our own cosmic backyard is a major discovery.

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 scientists believe that when the universe was about 380,000 years old the very first atoms of hydrogen formed. Eventually, they cooled enough to form stars and those stars became the first galaxies.

Researchers identified two populations of what they term "satellite galaxies" orbiting the Milky Way. The first consists of very faint galaxies said to have formed during the cosmic dark ages before there was light. The second population are slightly brighter and is thought to consist of galaxies that formed hundreds of millions of years later once the UV radiation emitted by the first stars cooled more.

This research has only been possible in the last decade or so. Ten years ago, the faintest of the galaxies near the Milky Way would have gone undetected. The team says that for a billion years or so no new galaxies were formed because changes made it harder for gases to cool. Eventually, enough dark matter gathered that the mass allowed ionized gasses to cool again resulting in the creation of super bright galaxies, such as the Milky Way.

SOURCE: University of Durham