The astronomical event that occurs when one celestial object moves into the shadow of another is called an eclipse.

There are two main types of eclipses:

* Solar eclipse: This occurs when the Moon passes between the Sun and Earth, blocking the Sun's light.

* Lunar eclipse: This occurs when the Earth passes between the Sun and Moon, casting its shadow on the Moon.

Eclipses can also occur between other celestial bodies, such as a planet and its moon, or even between two stars.