Lately, a surprising discovery about the evolution of our galaxy has been made. A large number of ancient stars were found in an unlikely region of our galaxy, the Milky Way. They formed the thin disk of the Milky Way several billion years earlier than previously believed.

The majority of stars are located in the thin disk of the Milky Way, where our solar system is. These stars follow an organized rotation around the galactic center.

The Sun is nearly five billion years old, making it a middle-aged star. It is also in the thin disk, which was thought to have started forming between eight and 10 billion years ago.

In order to gain a better understanding of how the Milky Way came to be, astronomers must create detailed maps of the galaxy that show the age, makeup, and movements of stars.

It is a challenge to create such maps because they require large datasets of stars with precise ages. So, astronomers often turn to studying old stars to look into the early days of the galaxy.

The old stars formed when only hydrogen, helium, and a bit of lithium were present in the universe. They are "less polluted" by heavier elements such as oxygen, carbon, or iron that were created and distributed by later generations of stars.

A team of astronomers from the Leibniz Institute for Astrophysics Potsdam used a dataset from the European Space Agency's Gaia mission to study stars about 3,200 light-years within the Sun.

They discovered many ancient stars that were over 10 billion years old. Some were over 13 billion years old.

"These ancient stars in the disk suggest that the formation of the Milky Way's thin disk began much earlier than previously believed, by about four to five billion years," said Samir Nepal, the lead author of the study.

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