• An eclipse is the complete or partial obscuring of a celestial body by another other. An eclipse occurs when three celestial objects become aligned.
  • The many eclipse phenomena known to astronomers are of two distinctly different types.
  • In the first, the eclipsing body comes between an observer and the eclipsed object; the latter appears to the observer totally or partly covered by the eclipsing object.
  • Eclipses of the Sun, occultations of stars by the Moon, transits of Venus or Mercury across the Sun’s disk, and eclipses of binary stars are of this kind.
  • Eclipses of the second type affect only planets or natural satellites that are not self-luminous.
  • In this case, the eclipsing body intervenes between the Sun and the eclipsed object.
  • The latter remains in view of the observer, but its illumination by the Sun is interrupted, and it becomes darkened by entering into the shadow of the eclipsing object.
  • Examples of this kind of eclipse phenomenon are eclipses of the Moon.