solar eclipse
An astronomical event where the moon passes between the sun and the earth, and the moon partially or completely covers the sun as viewed from a location on earth. This can only happen during a new moon, when the sun and moon are in conjunction as seen from earth.
A solar eclipse can be one of two major kinds: a partial eclipse, where the moon partially blocks out the sun; and a total eclipse, where the moon blocks out the sun completely and the sun's light creates a spectacular white ring around the moon.
Solar eclipses are frequently used in fiction to mark important, and often catastrophic, events in the plot.
This tag implicates eclipse (learn more).