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Questions about the predicted positions of an object in space, like another planet, comet, or asteroid.

In astronomy and celestial navigation, an ephemeris (plural: ephemerides) gives the trajectory of naturally occurring astronomical objects as well as artificial satellites in the sky, i.e., the position (and possibly velocity) over time. The etymology is from Latin ephemeris 'diary' and from Greek ἐφημερίς (ephemeris) 'diary, journal'.