Scientists have made a groundbreaking discovery at the center of the Milky Way galaxy, uncovering an ancient cluster of 18,000 stars that dates back to the infancy of our galaxy. The team, led by astronomer Hans-Walter Rix of the Max Planck Institute for Astronomy, used cutting-edge technology and the most accurate three-dimensional map of the Milky Way ever compiled, as well as a neural network that analyzed around two million stars, to make the discovery.
According to Rix, these stars are from a time when the Milky Way was just a compact collection of proto-galaxies coming together to form a larger entity. The team has dubbed this cluster of stars the “poor old heart” of the Milky Way.
The researchers used data collected by the European Space Agency’s (ESA) Gaia laboratory, which has been orbiting the Sun for years. Gaia’s measurements allowed scientists to estimate the stars’ metallicity, revealing when they were formed.
After the Big Bang 13.8 billion years ago, the primordial universe mainly consisted of hydrogen, with a little bit of helium. As stars began to form, their hot dense cores started to smash atoms together to form heavier elements – hydrogen into helium, helium into carbon, and so on.
The later a star forms in the universe, the more metals it is likely to have. The scientists found this group of two million stars had similar ages and metallicities and were more than 12.5 billion years old. This study significantly fleshes out the existing picture of the history of the Milky Way, and confirms the existence of a tightly bound in situ “iceberg” of ancient stars at the heart of our galaxy.