Appulse is the least apparent distance between one celestial object and another, as seen from a third body during a given period.
An appulse is an apparent phenomenon caused by perspective only; the two objects involved are not near in physical space.
In these cases, the two objects appear to approach each other, but turn away before reaching a momentary coincidence of right ascension.
When the celestial bodies appear so close together that one actually passes in front of the other, the event is classified as a transit, occultation, or eclipse, and not an appulse.
Appulses are naked-eye events for general observers when involving bright planets and the Moon.