UK astronomers discover first ever galaxies

UK astronomers discover first ever galaxies

Astronomers have discovered the first galaxies ever formed over 13 billion years ago.

UK astronomers, together with US colleagues, have found evidence that the faintest satellite galaxies orbiting our own Milky Way galaxy are amongst the very first formed in our universe.

Segue-1, Bootes I, Tucana II and Ursa Major I are thought to be over 13 billion years old. Our Universe is thought to be 13.8 billion years old.

Dr Alis Deason and Professor Carlos Frenk from Durham University’s Institute for Computational Cosmology (ICC), together with Dr Sownak Bose from Harvard-Smithsonian Center for Astrophysics in the US, identified two populations of satellite galaxies orbiting the Milky Way.

Professor Frenk, Director of Durham's 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.

“Our finding supports the current model for the evolution of our Universe, the ‘Lambda-cold-dark-matter model’ in which the elementary particles that make up the dark matter drive cosmic evolution.”

When the Universe was about 380,000 years old, the very first atoms formed. These were hydrogen atoms, the simplest element in the periodic table. These atoms collected into clouds and began to cool gradually and settle into the small clumps or “halos” of dark matter that emerged from the Big Bang.

This cooling phase, known as the “Cosmic dark ages”, 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. With the formation of the first galaxies, the Universe burst into light, bringing the cosmic dark ages to an end.

The research was part funded by UK Research and Innovation’s Science and Technology Facilities Council (STFC).

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Further information

Read more on the STFC website