Astronomers Trace 20 Metal-Poor Stars to Loki, a Dwarf Galaxy the Milky Way Devoured
Updated
Updated · CNN · May 23
Astronomers Trace 20 Metal-Poor Stars to Loki, a Dwarf Galaxy the Milky Way Devoured
6 articles · Updated · CNN · May 23
Twenty metal-poor stars about 7,000 light-years from the solar system appear to be debris from a single dwarf galaxy, dubbed Loki, that the Milky Way absorbed more than 10 billion years ago.
Gaia data and follow-up spectroscopy showed the stars share a chemical fingerprint despite split motions—11 in prograde orbits and nine in retrograde—supporting a common origin in an early merger.
Researchers say that mix of opposite orbital paths would fit a collision when the Milky Way was still smaller and weaker, likely within 3 to 4 billion years of the Big Bang.
If confirmed, Loki may have been a major merger nearly on the scale of Gaia-Sausage-Enceladus, implying a significant piece of the Milky Way’s formation history has been overlooked near the galactic disk.
Outside astronomers called the evidence intriguing but cautioned Loki could still prove to be part of a known system, with larger datasets needed to test whether it was a distinct galaxy.
How does the 'Loki' discovery rewrite our galaxy's violent origin story?
What other galactic ghosts are hiding in plain sight within the Milky Way's crowded disk?
Tracing the Milky Way’s Violent Past: 20 Metal-Poor Stars Linked to Ancient "Loki" Galaxy Merger
Overview
In May 2026, astronomers discovered 20 ancient, very metal-poor stars in our galactic neighborhood, identified as remnants of a lost dwarf galaxy called Loki. These stars are considered astronomical fossils because their extremely low metal content shows they formed in the early universe, preserving signatures from the first supernovae and neutron star mergers. By studying their metal content, scientists can determine their great age. The unusual orbits of these stars provide important clues about their origin, offering a rare glimpse into the Milky Way’s early history and how our galaxy formed through ancient mergers.