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"

Low-mass X-ray binaries are systems in which a star transfers matter onto a compact object—either a black hole or a neutron star—producing energetic outbursts. During these events, their optical spectra provide a way to study extreme processes of accretion and matter ejection. While some spectroscopic features have been analysed in detail (e.g., revealing disc expansion and the presence of optical winds), the appearance of broad absorptions in the optical regime has traditionally been neglected. In this work, we present the first systematic study of these broad absorptions. We carry out the