In the standard cosmological model (𝜦CDM), galaxies are merely the visible "tips of the icebergs," residing within massive, invisible cocoons of dark matter known as haloes. While these haloes dictate the evolution and motion of galaxies, measuring their true size and mass has long been one of the most challenging tasks in astrophysics. A new study published in Astronomy & Astrophysics by Claudio Dalla Vecchia and Ignacio Trujillo from the Instituto de Astrofísica de Canarias (IAC) proposes a breakthrough: a physically motivated definition of a galaxy’s edge that acts as a precision "ruler"

O ne of the key challenges in astronomy is to measure accurate distances to celestial objects. Knowing distances is crucial since it allows us to measure physical properties such as size, mass and luminosity. Since we can’t go out and use a tape-measure, a range of different approaches have been developed. Many of these approaches rely on using “standard candles”. Standard candles are objects (for example stars or supernovae) for which we know their intrinsic ”true” brightness. Once we know this, then their observed brightness compared to their intrinsic brightness gives us a distance to the

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