A new study published in The Astrophysical Journal investigates the use of RR Lyrae variable stars as tracers to explore the earliest phases of the Milky Way’s formation.
The research, led by Giuseppe Bono, involved researchers from the Department of Physics at the University of Rome Tor Vergata.
The study is based on the photometric and spectroscopic analysis of approximately 300,000 RR Lyrae stars, which made it possible to reconstruct in detail the three‑dimensional and “six‑dimensional” structure of our Galaxy (including position, distance, proper motions, radial velocity, and chemical composition).
By integrating the stellar orbits, the team was able to investigate the most remote epochs of Galactic evolution, providing direct evidence of the physical conditions under which the Milky Way was formed.
One of the most significant outcomes is the identification of a substantial population of RR Lyrae stars across the Galaxy’s major components, halo, thick disk, and thin disk, all exhibiting very similar properties.
This finding suggests that these structures formed over a relatively short timescale, on the order of 1–2 billion years, consistent with the monolithic collapse model proposed in the 1960s by Eggen, Sandage, and Lynden-Bell.
- INAF Press Release (Italian):
https://www.media.inaf.it/2026/01/26/rr-lyrae-formazione-via-lattea/ - Article in The Astrophysical Journal:
https://iopscience.iop.org/article/10.3847/1538-4357/ae2c60/pdf
Congratulations to our colleague Giuseppe Bono and the entire research team for this important scientific achievement!
Image Credit: INAF
