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A new study has revealed that the Milky Way's narrow disk might be far older than previously thought, due to the finding of ancient stars positioned startlingly near to our Sun. Researchers utilizing data from the European Space Agency's Gaia space observatory discovered that some of these stars originated less than a billion years after the Big Bang, making them over 13 billion years old.
This discovery calls into question the long-held view that the Milky Way's narrow disk, which contains the majority of stars, including the Sun, originated some 8 to 10 billion years ago. Instead, the new discoveries indicate that the creation of this area of the Galaxy occurred as much as 4-5 billion years earlier than previously assumed. This enormous chronology modification has the potential to fundamentally change our understanding of the Milky Way's history and evolution.
The researchers, lead by Samir Nepal, a doctorate candidate at Germany's Leibniz Institute for Astrophysics Potsdam (AIP), used powerful machine learning techniques to date these ancient stars. The scientists estimated the ages and metal composition of almost 800,000 stars in the solar neighbourhood, an area spanning roughly 3,200 light-years around the Sun, using data obtained by the Gaia satellite. The findings, published on the pre-print arXiv server and reported by AIP on July 31, demonstrate that several of these stars are more than 10 billion years old, with some reaching 13 billion years old.
The discovery of such old stars in the Milky Way's narrow disk is both startling and interesting. Given that the universe is around 13.8 billion years old, the presence of these stars indicates that this region of our galaxy originated extremely early in the universe's history, inside the first billion years following the Big Bang.
The study reveals an unexpected element of these old stars: their metal richness. Stars born in the early cosmos are metal-poor because the universe was mostly made up of hydrogen and helium.
