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seeing

(Encyclopedia)seeing, in astronomy, the clarity with which stars and other celestial objects can be observed. It is primarily determined by the atmosphere of the earth. The most obvious phenomenon is twinkling, whe...

Newcomb, Simon

(Encyclopedia)Newcomb, Simon no͞oˈkəm, nyo͞oˈ– [key], 1835–1909, American astronomer, b. Nova Scotia, grad. Lawrence Scientific School, Harvard, 1858. Living in the United States from 1853, he was appointe...

Van Allen, James Alfred

(Encyclopedia)Van Allen, James Alfred, 1914–2006, American physicist and space scientist, Mt. Pleasant, Iowa. A graduate (Ph.D 1939) of and professor of physics (1951–85) at what is now the Univ. of Iowa, where...

Brahe, Tycho

(Encyclopedia)Brahe, Tycho tīˈkō brä [key], 1546–1601, Danish astronomer. The most prominent astronomer of the late 16th cent., he paved the way for future discoveries by improving instruments and by his prec...

Sirius

(Encyclopedia)Sirius sĭrˈēəs [key], or Dog Star, brightest star in the sky. It is located in the constellation Canis Major (1992 position R.A. 6h44.8m, Dec. −16°42′); its Bayer designation is Alpha Canis M...

tektite

(Encyclopedia)tektite tĕktīt [key], naturally occurring, silica-rich (65%–80% SiO2) glass resembling obsidian and sometimes shale, and is normally jet black to olive green. They appear as small rounded or elong...

Tethys , in astronomy

(Encyclopedia)Tethys tēˈthĭs [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn III (or S3), Tethys is 659 mi (1060 km) in diameter, orbits Saturn at a mean dista...

United States Naval Observatory

(Encyclopedia)United States Naval Observatory, a federal astronomical observatory, located in Washington, D. C. It evolved from the Navy's oldest scientific institution, the Depot of Charts and Instruments, founded...

time , sequential arrangement of all events

(Encyclopedia)time, sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophi...

Hammerstein, Oscar, 2d

(Encyclopedia)Hammerstein, Oscar, 2d, 1895–1960, American lyricist and librettist, b. New York City, grad. Columbia, 1916; grandson of Oscar Hammerstein. His first success was Wildflower (1923), with music by Vin...