A more intricate picture of the early Milky Way
An international team of astronomers has used data from the Dark Energy Spectroscopic Instrument (DESI) together with a novel clustering algorithm to reveal that the previously assumed single Gaia‑Sausage/Enceladus component may actually comprise multiple origins.
Methodology and data set
DESI provides high‑precision spectra for millions of stars in the Galactic halo. By grouping stars according to their chemical abundances and orbital parameters, the algorithm identified sub‑populations that differ in age, metallicity and orbital energy.
Implications for galactic models
The findings indicate that what was once interpreted as a single massive satellite merger likely represents a series of staggered accretion events involving smaller dwarf galaxies. This could substantially revise current models of the Milky Way’s mass distribution and assembly history.
Future work
The researchers stress that further observations, including data from the Gaia mission and upcoming spectroscopic surveys, are required to definitively assign the identified sub‑structures and to refine the timeline of these ancient mergers.