A Ghost Galaxy Called Loki Is Lurking in the Milky Way

A small group of 20 stars in our galaxy should not be where they are. They are ancient, chemically primitive and moving in wild, looping orbits through the galactic plane. They look, to anyone paying close attention, like someone else's stars.

A team of astronomers studied these 20 stars and believe they formed together in a dwarf galaxy they call "Loki," one that merged with the Milky Way during its early evolution. The name is apt: the Norse trickster god is known for appearing where he doesn't belong, wearing someone else's face.

Astronomers can identify stars that arrived from elsewhere by examining orbital behavior and chemical composition. A star's chemistry works like a fossil record, encoding the specific mix of supernovae, hypernovae and neutron star collisions that preceded its birth. These 20 stars show a narrower spread in chemical abundances than typical halo stars at the same metallicity and, crucially, they resemble each other far more than they resemble the Milky Way.

Eleven of the 20 move in the same rotational direction as most of the galaxy (prograde orbits); nine move in the opposite direction (retrograde). Different directions, identical chemistry. The most straightforward explanation: when this small galaxy crashed in, its stars got scattered into both orbital directions while retaining their shared chemical identity.

Researchers estimate Loki would have had a total mass around 1.4 billion times that of our Sun. That mass is omparable to some of the classical dwarf galaxies visible today, like the Magellanic Clouds. The findings stop short of certainty; lead author Federico Sestito acknowledged that more observations are needed. High-resolution spectroscopy is time-intensive work, requiring roughly 4 hours of telescope time per star, which is why the sample remains small.

Twenty stars. A ghost galaxy, reassembled from chemistry and motion, dissolved into our own sky 10 billion years ago is now answering to its name.

Read the full story at Live Science, May 13, 2026

Hot Take: The Milky Way consumed Loki so completely it left faint evidence. The 20 stars that remain are the receipt.