Loki Galaxy: Milky Way's Ancient Meal Revealed

An unusual cluster of 20 metal-poor stars may be the remnants of a dwarf galaxy, nicknamed Loki, that the Milky Way absorbed approximately 10 billion years ago. This discovery provides a potential missing piece in understanding the Milky Way's formation history from about 10 billion years ago. Initially, the stars' orbital patterns puzzled researchers, leading to the nickname Loki, after the Norse trickster god.

The Milky Way grew significantly by merging with smaller dwarf galaxies over billions of years. Astronomers are actively searching for evidence of these consumed galaxies to reconstruct its evolution. The newly identified metal-poor stars, found unexpectedly close to the galactic disk, are composed primarily of hydrogen and helium, indicating their ancient origins.

These stars' chemical composition and location suggest they originated from a single, large dwarf galaxy devoured by the Milky Way early in its existence. Some stars exhibit prograde orbits, aligning with the galactic disk's rotation, while others have retrograde orbits, moving in the opposite direction.

This dual orbital pattern suggests the merger occurred when the Milky Way was much smaller and its gravitational pull was weaker, likely within the first 3 to 4 billion years after the Big Bang. The remnants of Loki, though difficult to locate near the disk, could significantly alter current models of the Milky Way's growth.