Astronomers Trace 20 Metal-Poor Stars to 1.4-Billion-Solar-Mass Loki Galaxy

3 articles · Updated · Livescience.com · May 13

Twenty very metal-poor stars orbiting unusually close to the Milky Way’s disk appear to be debris from an ancient dwarf galaxy nicknamed Loki, rather than native disk stars.
Chemical fingerprints from Canada-France-Hawaii Telescope spectra and orbital data from Gaia showed the stars sit within about 6,500 light-years of the sun yet behave unlike typical younger, metal-rich disk stars.
Computer simulations suggest a single merger more than 10 billion years ago—around 3 billion years after the Big Bang—could scatter Loki’s stars into both prograde and retrograde orbits seen today.
The models put Loki’s mass at roughly 1.4 billion suns, implying it may have been one of the earliest small galaxies later absorbed as the Milky Way assembled.
Researchers and outside astronomers said the case is promising but unconfirmed, with high-resolution follow-up on larger samples needed to rule out a Milky Way substructure instead.

Why are Loki's remnants hiding in the Milky Way's busy disk instead of the distant halo?

Could the ghost galaxy Loki be a statistical illusion created by biases in our astronomical data?

What does this ancient galactic collision teach us about the origin of gold in our solar system?