Much more discussion and detail is in the paper itself, and we build upon the fantastic work done by several groups to piece together a plausible history of our Galaxy.

You can see a movie of this simulated galaxy's evolution here: youtube.com/watch?v=1q1T...

Making and staring at movies like these was by far one of the highlights of my job so far.

We interpret our findings using the IllustrisTNG50 cosmological simulation, finding one particularly similar analog that perhaps provides clues about our own Galaxy's formation story, chiefly a decisive major merger that thickens the old disk and seeds the young disk

Using Gaia-based alpha abundances from Jiadong Li, we can isolate high-alpha stars that obey a well-behaved age-metallicity relation. This panel therefore truly represents a time-ordered 'portrait' of the birth of the Milky Way disk across ~5 billion years

Illustrating the orbital 'circularity' distribution as a function of metallicity - a rough proxy for cosmic time - we find a distinct three-phase behavior roughly corresponding to the protogalaxy, 'spinup' to an early disk, and 'cooldown' to a young disk.

We assemble an all-sky sample of 10 million red giant stars with metallicities and 6D motions from Gaia to ask a simple question: how did the the orbital structure our galaxy evolve over time?