7472 20250204104903.0 10.48550/arXiv.2412.05671 DOI BKSECT-2025-0003 Mahy, L Basic stellar observables 2024 Physical properties of stars such as luminosity, surface temperature, distance, or mass are measured from observations. These physical properties are of paramount importance to understand how stars are born, live, and die in the universe near and far. This chapter discusses the basic concepts used by astronomers to derive key information about stars from the light they emit. We present through a pedagogical approach the methods required for determining stellar brightness (apparent and absolute magnitudes), surface temperature (via black-body radiation and spectral classification), and distance (using parallax and standard candles). We finally review techniques for estimating stellar mass and radius, including the use of binary star systems and stellar evolution models. NO Encyclopedia of Astrophysics Ilya Mandel, section editor F.R.N. Schneider Elsevier laurent.mahy@ksb-orb.be 4779597 http://publi2-as.oma.be/record/7472/files/Mahy_Book_2024.pdf 3080 http://publi2-as.oma.be/record/7472/files/Mahy_Book_2024.gif?subformat=icon icon 4019 http://publi2-as.oma.be/record/7472/files/Mahy_Book_2024.jpg?subformat=icon-180 icon-180 BOOKSECT