Recently, astronomers have identified some of the oldest galaxies in the universe. They began to form only about 100 million years after the Big Bang.
Astronomers from the Institute for Computational Cosmology at Durham University and the Harvard-Smithsonian Center for Astrophysics were studying dark matter when they identified the earliest galaxies. According to the study, the faintest satellite galaxies orbiting our galaxy are amongst the very first galaxies that formed in our Universe.
These galaxies are about 13 billion years old, meaning they began to form only about 100 million years after the Big Bang.
However, the new study was extremely exciting for the researchers.
Professor Carlos Frenk, Director of Durham University’s Institute for Computational Cosmology, 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.
The Oldest Galaxies
Some of the oldest galaxies identified in the latest study are Segue-1, Bootes I, Tucana II and Ursa Major I.
So, currently, we know that the early universe was not even transparent to radiation. The very first atoms formed 380,000 years after the big bang, in a period known as the Dark Ages. These atoms collected into clouds and began to gradually cool and settle into small clumps or “halos” of dark matter, the study says.
After some time, the gas that had cooled inside the clouds began to form stars. These objects became the first galaxies to have formed in our universe. Thus, the dark ages ended and the universe began to burst into light.
The team identified two populations of satellite galaxies orbiting the Milky Way. One group was fainter and formed during the era before dark matter halos were built up. The other one was slightly brighter forming hundreds of millions of years later.
The team also found that a model of galaxy formation that they had developed previously agreed perfectly with the data. Therefore, allowing them to infer the formation times of the satellite galaxies.
The study was published Thursday in the Astrophysical Journal.
Thumbnail image: The distribution of satellite galaxies orbiting a computer-simulated galaxy, as predicted by the Lambda-cold-dark-matter cosmological model. Credit: Institute for Computational Cosmology, Durham University, UK / Heidelberg Institute for Theoretical Studies, Germany / Max Planck Institute for Astrophysics, Germany.