About solar, lunar and space weather

Sunrise and sunset times depend on your latitude, longitude and date. They are computed from the Sun's position; civil, nautical and astronomical twilight are defined by the Sun's elevation below the horizon (e.g. −6°, −12°, −18°). The Moon's phases follow the synodic month (new to full and back); illumination and rise/set times are used by astronomers and the public (NASA; USNO).

The Kp index measures global geomagnetic activity on a 0–9 scale and is used to estimate aurora visibility at mid-latitudes. Higher Kp (e.g. 5–7) can bring aurora to lower latitudes; values come from ground-based magnetometers. Geomagnetic storms are driven by the solar wind and coronal mass ejections; NOAA's Space Weather Prediction Center and similar services provide forecasts (NOAA SWPC; WMO).

Space weather affects satellites, communications and power grids. The solar cycle (about 11 years) influences the frequency of flares and CMEs. Human spaceflight (e.g. ISS) and space station passes are predictable from orbital mechanics; data on this page may use APIs from NASA, NOAA or other space agencies. Meteor showers occur when Earth crosses comet debris; peak rates and dates are published by the IMO and NASA.