Chemical Fingerprints Uncover Hidden Spiral Arms in the Milky Way
An international team, led by Carlos Viscasillas Vázquez, has used stellar chemical fingerprints to reveal previously unseen spiral arms in the Milky Way. By analyzing elemental clues, specifically metallicity and magnesium-to-iron ratios, in 5,000 stars, researchers outlined two inner spiral arms—Scutum and Sagittarius—and a faint connecting spur. This novel spectroscopic approach offers a deeper understanding of the galaxy's crowded regions, demonstrating how chemical patterns serve as durable records of star formation and evolution, challenging traditional mapping methods.
An international team of astrophysicists has unveiled hidden structures within the Milky Way, specifically two inner spiral arms and a linking spur, by analyzing the chemical compositions of stars. Led by Carlos Viscasillas Vázquez of Vilnius University, the research utilized elemental clues in roughly 5,000 stars, moving beyond traditional star counts to understand galactic architecture. The team focused on spectroscopic data from the Gaia-ESO Survey on the Very Large Telescope, mapping regions where elements like iron and magnesium varied in abundance. This technique identifies metallicity and the magnesium-to-iron ratio, key tracers that differentiate stars enriched by fast core-collapse supernovae versus slower Type Ia events, providing insights into star formation histories. The study successfully mapped the Scutum and Sagittarius arms near the Galactic center and identified a short, arm-like bridge connecting them. Dr. Laura Magrini noted that subtle chemical differences made these arms clearly emerge, while Vázquez emphasized the close connection between stellar dynamics and chemistry, as spiral arms enhance star formation and leave distinct chemical signatures. This approach allows astronomers to compare regions formed under different conditions, connect local structures to larger spiral features, and trace changes across the galactic disk's height, even through dense dust. Published in Astronomy & Astrophysics, this work demonstrates that stellar chemistry offers a powerful new lens for mapping and understanding the Milky Way’s complex evolution.
