perigee

Definition

The point, in an orbit about the Earth, that is closest to the Earth: the periapsis of an Earth orbiter.

Etymology

From French périgée via Latin perigeum, perigaeum, ultimately from Ancient Greek περί (perí, “near”) + γῆ (gê, “Earth”).

Example Sentences

• "As the moon wheels around Earth every 28 days and shows us a progressively greater and then stingier slice of its sun-lightened face, the distance between the moon and Earth changes, too. At the nearest point along its egg-shaped orbit, its perigee, the moon may be 26,000 miles closer to us than it is at its far point."
• "Conjunctions of I and II [Io and Europa] occur when they are near perigee and apogee respectively; conjunctions of II and III [Europa and Ganymede] occur when II [Europa] is near perigee."
• "The resolution of the images obtained by this American probe [Messenger] will depend on its altitude [above Mercury] at any one time: about ten meters at perigee (200km altitude), but only one 1 km at apogee (15000km)."

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