Galactic archaeology

Galactic archaeology reconstructs a galaxy’s formation and evolution from the chemical compositions, ages, and motions of its stars, especially in the Milky Way.

Stellar kinematics: The motions and velocity distribution of stars within a galaxy or stellar system. Orbital patterns help distinguish stars formed in the Milky Way from stars added through mergers.
Metallicity: In astronomy, the abundance of elements heavier than helium in an astronomical object. Metallicity tracks how much earlier generations of stars enriched the gas from which a star formed.
Gaia-Enceladus: A massive dwarf galaxy whose ancient merger with the Milky Way is inferred from its stars’ motions and chemistry. Its debris is a landmark example of identifying an accreted galaxy in the stellar halo.
Walter Baade: A German-American astronomer who distinguished stellar populations by their locations and properties in galaxies. His population concept helped establish that galaxies contain stars with different histories.
Cosmological simulations: Computational models that simulate the formation and evolution of cosmic structures under physical laws. Simulations predict histories to compare with those inferred from observed stellar records.
Stellar spectroscopy: The study of stars through the wavelengths and strengths of their emitted or absorbed light. Spectral lines reveal the elemental abundances used to trace stellar origins.
Abundance ratio: The relative abundance of two chemical elements in an astronomical object, often compared with the solar ratio. Element ratios can distinguish enrichment by different stellar sources and timescales.
Helmi streams: Groups of halo stars identified by coherent motions and associated with an ancient accretion event. Their discovery showed that disrupted stellar systems can remain recognizable in orbital data.
Olin Eggen: An American astronomer who studied stellar motions and proposed a rapid collapse model for the Milky Way. His work made stellar kinematics central to theories of Galactic formation.
Extragalactic astronomy: The study of astronomical objects and phenomena beyond the Milky Way. Most other galaxies cannot be resolved into as many individual stellar histories.

Linked from 14 pages