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solar energy

(Encyclopedia)solar energy, any form of energy radiated by the sun, including light, radio waves, and X rays, although the term usually refers to the visible light of the sun. Solar energy is needed by green plants...

solar plexus

(Encyclopedia)solar plexus, dense cluster of nerve cells and supporting tissue, located behind the stomach in the region of the celiac artery just below the diaphragm. It is also known as the celiac plexus. Rich in...

solar system

(Encyclopedia)CE5 Solar system CE5 solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the ...

solar time

(Encyclopedia)solar time, time defined by the position of the sun. The solar day is the time it takes for the sun to return to the same meridian in the sky. Local solar time is measured by a sundial. When the cente...

solar wind

(Encyclopedia)solar wind, stream of ionized hydrogen—protons and electrons—with an 8% component of helium ions and trace amounts of heavier ions that radiates outward from the sun at high speeds. The continuous...

Lockyer, Sir Joseph Norman

(Encyclopedia)Lockyer, Sir Joseph Norman lŏkˈyər [key], 1836–1920, English astronomer, educated on the Continent. One of the first to make a spectroscopic examination of the sun and stars, he devised (1868), i...

transit

(Encyclopedia)transit, in astronomy, passage of a body across a meridian or passage of a small body across the visible disk of a larger one. (The passage of a large body across a smaller one is called an eclipse or...

Janssen, Pierre Jules César

(Encyclopedia)Janssen, Pierre Jules César pyĕr zhül sāzärˈ zhäNsĕnˈ [key], 1824–1907, French astronomer. In 1857–58, in Peru, he worked on the determination of the magnetic equator; in the Azores (1867...

Secchi, Pietro Angelo

(Encyclopedia)Secchi, Pietro Angelo pyĕˈtrō änˈjālō sĕkˈkē [key], 1818–78, Italian astronomer, a Jesuit priest. He was director of the observatory of the Gregorian Univ., Rome, from 1849. He is known es...

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...