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Hyperion, in astronomy

(Encyclopedia)Hyperion hīpērˈēən [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn VII (or S7), Hyperion is the largest highly irregular (nonspherical) body in...

equation of time

(Encyclopedia)equation of time: see solar time. ...

Port Augusta

(Encyclopedia)Port Augusta, city (2016 pop. 13,808), South Australia, S Australia, at the head of Spencer Gulf. It is a railroad center and a center for solar and other renewable energy. ...

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...

anomalistic year

(Encyclopedia)anomalistic year ənŏmˌəlĭsˈtĭk [key], time required for the earth to go from the perihelion point once around the sun and back to the perihelion point. It is 365 days, 6 hr, 13 min, 53.0 sec of...

Laplace, Pierre Simon, marquis de

(Encyclopedia)Laplace, Pierre Simon, marquis de pyĕr sēmôNˈ märkēˈ də läpläsˈ [key], 1749–1827, French astronomer and mathematician. At 18 he went to Paris, proved his gift for mathematical analysis to...

geomorphology

(Encyclopedia)geomorphology, study of the origin and evolution of the earth's landforms, both on the continents and within the ocean basins. It is concerned with the internal geologic processes of the earth's crust...

Enceladus

(Encyclopedia)Enceladus ĕnsĕlˈədəs [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn II (or S2), Enceladus is 310 mi (500 km) in diameter, orbits Saturn at a m...

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...

sidereal time

(Encyclopedia)sidereal time (ST), time measured relative to the fixed stars; thus, the sidereal day is the period during which the earth completes one rotation on its axis so that some chosen star appears twice on ...