Hidden Ancient Galaxy 'Loki' Discovered Inside the Milky Way, Study Reveals

An ancient galaxy has been discovered buried within the Milky Way, according to new research. Astronomers have identified traces of a lost realm, dubbed “Loki” after the Norse trickster god, which was consumed by our galaxy billions of years ago as it expanded.

The findings, published in the Monthly Notices of the Royal Astronomical Society, suggest that Loki, if confirmed, was a dwarf galaxy—a type of galaxy containing no more than a few billion stars, far fewer than the hundreds of billions in mature galaxies like the Milky Way. Dwarf galaxies often orbit larger galaxies and are of significant interest to astronomers studying their irregular shapes and formation processes.

One key question is whether dwarf galaxies form through gravitational interactions that merge them into larger galaxies or through the influence of invisible dark matter. Additionally, dwarf galaxies typically consist of “metal-poor” stars, similar to the first stars that emerged in the universe before heavier elements were forged by later generations.

How Astronomers Detected the Hidden Galaxy

The researchers analyzed a group of 20 metal-poor stars located in the Milky Way’s galactic plane—the flat, disc-shaped region where most of the galaxy’s stars reside. By comparing the chemical composition of these stars to objects in the galaxy’s outer regions, including other stars and dwarf galaxies, they identified traces of numerous cosmic explosions, such as supernovas and neutron star mergers.

However, a critical observation emerged: no traces of white dwarf explosions were found. White dwarfs are the dense cores of medium-mass stars like our Sun, formed after billions of years. The absence of such traces suggests that the 20 stars originated from an extremely short-lived dwarf galaxy that never produced white dwarfs.

Orbital Clues Point to a Chaotic Past

Another intriguing aspect of the suspected dwarf galaxy is the diverse orbital directions of its stars. Eleven stars orbit in the same direction as the Milky Way’s rotation (prograde orbit), while nine orbit in the opposite direction (retrograde orbit). Astronomers attribute this to an “early accretion” event, where Loki merged with the Milky Way when our galaxy was still young and its orbits were chaotic, disrupting the dwarf galaxy’s original stellar motions.

This discovery adds to the growing body of evidence that the Milky Way has absorbed multiple smaller galaxies over its lifetime, reshaping its structure and stellar population in the process.