A series of objects aged between 12 to 13 billion years have recently been discovered in the halo of the Milky Way, the galaxy that contains Earth.
According to Professor Anna Frebel from the Massachusetts Institute of Technology (MIT), the objects found in the Milky Way are extremely ancient stars, born at a time when the first galaxies were forming in the universe.
They date back to 12-13 billion years, a brief time after the Big Bang—an event that marked the birth of the universe, according to a research summary on Sci-News.
The Milky Way captured from the Very Large Telescope (VLT) system of the European Southern Observatory (ESO) – (Photo: ESO).
These ancient stars were certainly not formed within the bright band of the Milky Way that we see in the sky, but belong to much older dwarf galaxies.
These primordial galaxies may have been located too close to where the Milky Way eventually formed.
The galaxy that contains Earth is classified as a “monster” galaxy in the universe, developing rapidly. Consequently, this “descendant” quickly engulfed the smaller primordial galaxies around it, absorbing the ancient stars into its halo.
Although we often refer to it as a “band,” the Milky Way is actually a spiral galaxy with a circular central star disk. Earth resides at the edge of this disk.
Meanwhile, the primordial stars wander in the halo of the galaxy, a fainter spherical structure that envelops the main disk.
The discovery of these ancient stars is a treasure for astronomers.
This is because studying “the children of the Big Bang”—the term scientists use for the first objects born when the universe formed—is incredibly challenging.
Despite having advanced tools like the James Webb Space Telescope, which can traverse billions of years of space-time to capture ancient images, all they have found are extremely faint dwarf galaxies.
Therefore, capturing these “fossils” of the early universe right within the Milky Way presents a fantastic opportunity to study the nature of these objects more clearly.
The ancient origins of the stars have also been determined through preliminary analyses, indicating that they share similar compositions with the ancient dwarf galaxies identified in previous studies.
Additionally, the monitoring of three of these stars—located 30,000 light-years away from Earth—reveals movements entirely different from the stars in the main disk.
This movement suggests that they once belonged to another parent galaxy, which was absorbed by the Milky Way as it grew.
The absorption of other galaxies is common for large galaxies like the Milky Way. It is estimated that the galaxy we inhabit has absorbed over 20 galaxies since its formation, including quite large ones, to achieve its current size and complex structure.
The method for searching for ancient stars recently applied by the MIT team promises to help identify a series of stars and other primordial objects hidden among the more than 400 billion stars in the Milky Way, also opening a door into the dawn of the universe.
The research was recently published in the scientific journal Monthly Notices of the Royal Astronomical Society.
