Eclipses

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.