Ancient galaxies orbiting the Milky Way are oldest ever discovered and were born in ‘cosmic dark age’

Four small galaxies orbiting the Milky Way could be the oldest in the universe, scientists have claimed.

British astronomers say the galaxies date back more than 13 billion years and were born shortly after the Big Bang.

The galaxies Segue-1, Bootes I, Tucana II and Ursa Major I are very faint because they were among the first that ever formed, coming into being more than 13 billion years ago.

An image of one of the ‘ultra-faint’ ancient galaxies (Picture: Durham University)

Professor Carlos Frenk, director of Durham’s Institute for Computational Cosmology (ICC), said: ‘Finding some of the very first galaxies that formed in our universe orbiting in the Milky Way’s own backyard is the astronomical equivalent of finding the remains of the first humans that inhabited the Earth. It is hugely exciting.’

When the universe was about 380,000 years old the very first atoms were born. These were tiny particles of hydrogen – the simplest element in the periodic table.

As they collected into clouds and began to cool they gradually settled into the small clumps or ‘halos’ of dark matter that emerged from the Big Bang.

The Milky Way galaxy is home to hundreds of billions of stars, one of which has a nice little planet called Earth orbiting it (Photo by Davis Meltzer/National Geographic/Getty Images)

This cooling phase is known as ‘cosmic dark ages’ -and lasted about 100 million years. Eventually, the gas that had cooled inside the halos became unstable and began to form stars.

These objects are the very first galaxies ever to have formed and caused the universe to burst into light – bringing the cosmic dark ages to an end.

Dr Alis Deason, a Royal Society University Research Fellow at the ICC, said: ‘This is a wonderful example of how observations of the tiniest dwarf galaxies residing in our own Milky Way can be used to learn about the early Universe.’


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