👉 Horizons are an important concept in astrophysics and cosmology. They refer to the regions or areas of space where objects like stars, galaxies, and black holes move slowly relative to one another. These regions may be stationary or moving due to different gravitational effects such as gravity from other objects or through the expansion of the universe. For example, a galaxy is considered to have multiple horizons because it moves with respect to its own background light. This means that stars in the galaxy are observed at