The most massive stars in the universe are often born and evolve in binary and multiple systems — that is, in pairs or groups bound by their mutual gravity. Understanding how they interact with each other is key to explaining everything from their formation to the impact they have on the galaxies they inhabit. The MONOS project (Multiplicity Of Northern O-type Spectroscopic systems) aims to study these systems in the northern sky, combining spectroscopic observations (which analyze light split into its component colors to measure stellar velocities and physical properties) with photometry

Measuring galaxy sizes is essential for understanding how they were formed and evolved across time. However, traditional methods based on l ight concentration or isophotal densities often lack a clear physical meaning. A recent study from Trujillo+20 explores a more physically motivated definition: the radius R 1, where the stellar surface density falls to 1 solar masses per parsec square —roughly the threshold for gas to form stars in galaxies like the Milky Way. In this work, Arjona-Gálvez+25 uses over 1,000 galaxies from several state-of-the-art cosmological simulations (AURIGA, HESTIA

Research on the formation, origin, and evolution of the dichotomy between the thin and thick disk components of the Milky Way has been a major topic of study, as it is key to understanding how our Galaxy formed. However, this is not an easy task, since populations defined by their morphology or kinematics show a mixture of chemically distinct stellar populations. Age therefore becomes a fundamental parameter for understanding the evolution of the Galactic disk. Our goal is to derive the age and metallicity distributions of the thin and thick disks defined kinematically, in order to reveal