nadir
n.n. the lowest point in the sky that a star or planet reaches. It is the opposite of the highest point, called the zenith.
n. the lowest point in the sky reached by a celestial body, specifically the point where it is farthest from the zenith. Often used in astronomical contexts to describe the position of a star or planet relative to an observer.
The star reached its nadir just before midnight.
As the planet moved toward its nadir, the light from its surface became much dimmer and harder to observe.
The astronomer noted that the comet's trajectory would bring it to its nadir within the next hour, providing a unique opportunity for high-resolution imaging of its tail.
From Medieval Latin nadir, from Arabic نَظِير السَّمْت (naẓīr as-samt), composed of نَظِير (naẓīr, “counterpart, corresponding to”) and السَّمْت (as-samt, “the zenith”).