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ring, in astronomy

(Encyclopedia)ring, in astronomy, relatively thin band of rocks and dust and ice particles that orbit around a planet in the planet's equatorial plane. All four of the giant planets in the solar system—Jupiter, S...

precession of the equinoxes

(Encyclopedia)CE5 Precession of the equinoxes (the points at which the earth's celestial equator intersects its ecliptic) is due to the slow rotation of the earth's axis around a perpendicular to the ecliptic. ...

Ring nebula

(Encyclopedia)Ring nebula, planetary nebula in the northern constellation Lyra; cataloged as M57 or NGC 6720. It is perhaps the most famous and beautiful nebula of this type. Its name describes the appearance of th...

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...

week

(Encyclopedia)week, period of time shorter than the month, commonly seven days. The ancient Egyptians used a 10-day period, as did the French under the short-lived French Revolutionary calendar. In many regions a f...

Kuiper, Gerard Peter

(Encyclopedia)Kuiper, Gerard Peter or Gerrit Pieter gĕrˈĭt pēˈtər kīˈpər [key], 1905–73, American astronomer, b. the Netherlands. Kuiper is considered to be the father of modern planetary science for his...

Coblentz, William Weber

(Encyclopedia)Coblentz, William Weber kōˈblĕnts [key], 1873–1962, American physicist, b. North Lima, Ohio, grad. Case School of Applied Science (B.S., 1900) and Cornell (Ph.D., 1903). From 1905 to 1945 he was ...

Shasta, Mount

(Encyclopedia)Shasta, Mount shăsˈtə [key], volcanic peak, 14,162 ft (4,317 m) high, N Calif., in the Cascade Range. Visited c.1827 by Peter Skene Ogden, a British fur trader and explorer, Mt. Shasta has long bee...

Atlas, in astronomy

(Encyclopedia)Atlas, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn XV (or S15), Atlas is a small, irregularly shaped (nonspherical) body measuring about 25 mi (40 km) ...

Pan, in astronomy

(Encyclopedia)Pan, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn XVIII (or S18), Pan is 12.5 mi (20 km) in diameter, orbits Saturn at a mean distance of 83,000 mi (133...