Astrophysics

How astronomers measure distances: parallax, Cepheids, Type Ia supernovae, TRGB, Tully–Fisher, BAO, CMB, standard sirens, the Hubble constant, and its tension.

Transit, radial velocity, imaging, microlensing, and astrometry—how exoplanets are discovered and characterized, with tools, pitfalls, and what comes next.