The Universe is not distributed uniformly. Galaxies are arranged in a gigantic cosmic web made of voids, filaments, and galaxy clusters. These filaments act as enormous “cosmic highways” through which matter and galaxies flow toward the densest regions of the Universe. Understanding how these structures influence galaxy evolution is one of the major goals of modern astrophysics. In this work, we analyzed hundreds of thousands of galaxies from the Sloan Digital Sky Survey (SDSS) to study how galaxy density changes around cosmic filaments in the nearby Universe. Our main goal was to determine

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

The Necklace nebula is a bipolar, post-common-envelope planetary nebula, the central star of which has been shown to have a dwarf carbon star companion. We aim to understand the origins of the Necklace and its dwarf carbon central star. We study the carbon abundance of the nebula through far-ultraviolet spectroscopy obtained with the Hubble Space Telescope. Furthermore, through simultaneous modelling of multi-band light and velocity curves, we attempt to constrain the parameters of the central star system. Puzzlingly, we find that the region of the inner nebula observed with the Hubble Space