Eclipse Facts

An eclipse is an astronomical event. It is a process that develops slowly across time when one object in the sky moves into the shadow of another such object. The term eclipse is most often used to describe a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth. See the fact file below for more information about eclipses.

  • A lunar eclipse occurs when the moon passes behind the earth so that the earth blocks the sun’s rays from striking the moon.
  • A solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially covers the Sun as viewed from some locations on Earth.
  • A Solar eclipse always occurs two weeks before or after a lunar eclipse.
  • Lunar eclipses can only occur during a full moon. Solar eclipses can only occur during a new moon.
  • Eclipses very often occur in threes, alternating lunar, solar and lunar.
  • The maximum time a lunar eclipse can last is 3 hours and 40 minutes. The maximum time for a total solar eclipse is 7 minutes and 40 seconds.
  • Lunar eclipses can occur up to 3 times a year. Solar eclipses can occur at least 2 and no more than 5 times a year.
  • Lunar eclipses are visible over an entire hemisphere. Solar eclipses are visible in a narrow path a maximum of 167 miles wide.
  • The cycle of eclipses repeats every 18.6 years called the saros.
  • The eclipse shadow moves at 2,000 mph at the Earth’s poles and 1,000 mph at the Earth’s equator.