Light distributed in outdoor areas where light is not desired. Light pollution is typically caused by outdoor lighting fixtures which may emit a substantial amount of light in an upward direction. This creates a "haze" of light in the atmosphere that cannot be efficiently utilized.
environmental pollution consisting of harmful or annoying light.
The illumination of the night sky caused by artificial light sources on the ground (streetlights, billboards, etc.). Both the light and the loss of contrast make it difficult to find fainter stars and nebulae. This is becoming a bigger problem for both amateur and professional astronomers.