User:Hftf/Books/Astro/A1

A

 * Absolute magnitude
 * Absorption band
 * Abundance of the chemical elements
 * Accelerating universe
 * Accretion disc
 * Active galactic nucleus
 * Active galaxy
 * Age of the universe
 * Albedo
 * Algol variable
 * Alternatives to general relativity
 * Andromeda Galaxy
 * Andromeda–Milky Way collision
 * Angular diameter
 * Angular resolution
 * Anisotropy