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occultation

(Encyclopedia)occultation ŏkˌəltāˈshən [key], in astronomy, eclipse of one celestial body by another, e.g., when the moon lies between a star and the earth. Occultations of stars by the moon are important in ...

Selene

(Encyclopedia)Selene səlēˈnē [key], in Greek mythology and mythology, moon goddess; daughter of the Titans Hyperion and Theia and sister of the sun god Helios. There was no known moon cult among the Greeks, but...

ephemeris time

(Encyclopedia)ephemeris time (ET), astronomical time defined by the orbital motions of the earth, moon, and planets. The earth does not rotate with uniform speed, so the solar day is an imprecise unit of time. Ephe...

Shepard, Alan Bartlett, Jr.

(Encyclopedia)Shepard, Alan Bartlett, Jr., 1923–98, American astronaut, b. East Derry, N.H., grad. Annapolis, 1944. He served on a destroyer during World War II and later had extensive experience as a test pilot....

radar astronomy

(Encyclopedia)radar astronomy, application of radar to the determination of distances and planetary features within the solar system, such as rotation rates. A short burst of radio waves is transmitted in the direc...

Hipparchus, Greek astronomer

(Encyclopedia)Hipparchus, fl. 2d cent. b.c., Greek astronomer, b. Nicaea, Bithynia. He is the first systematic astronomer of whom there are records. He made his observations chiefly on the island of Rhodes. Ptolemy...

space exploration

(Encyclopedia)CE5 Moon mission assembly CE5 Stages in a moon mission shown counterclockwise from launching on the first day to splashdown on the ninth day. space exploration, the investigation of physical co...

satellite, natural

(Encyclopedia)satellite, natural, celestial body orbiting a planet, dwarf planet, asteroid, or star of a larger size. The most familiar natural satellite is the earth's moon; thus, satellites of other planets are o...

Cyrano de Bergerac, Savinien

(Encyclopedia)Cyrano de Bergerac, Savinien sävēnyăNˈ sēränōˈ də bĕrzhəräkˈ [key], 1619–55, French novelist. Satirizing the customs and beliefs of his time, he wrote two fantastic romances about visit...

node

(Encyclopedia)node, in astronomy, point at which the orbit of a body crosses a reference plane. One reference plane that is often used is the plane of the earth's orbit around the sun (ecliptic). Since the moon's o...