spicule

spicule
/spik"yoohl/, n.
1. a small or minute, slender, sharp-pointed body or part; a small, needlelike crystal, process, or the like.
2. Zool. one of the small, hard, calcareous or siliceous bodies that serve as the skeletal elements of various marine and freshwater invertebrates.
3. Astron. a jet of gas several hundred miles in diameter rising from the sun's surface to heights of 3000 to 6000 miles (4800 to 9600 km).
[1775-85; < L spiculum spearhead, arrowhead, bee stinger, equiv. to spic(a) ear of grain (see SPICA) + -ulum -ULE]

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▪ solar feature
 a jet of dense gas ejected from the Sun's chromosphere. Spicules occur at the edges of the chromospheric network, where magnetic fields (magnetic field) are stronger. They extend up to 10,000 km (6,000 miles) and, although they fall back to the Sun, are thought to contribute to the solar wind by feeding material into the corona.

      About 100,000 spicules are active on the Sun's surface at any given time. They rise from the lower chromosphere at about 20 km (12 miles) per second to a height of several thousand kilometres, and then within 10–15 minutes they disperse or collapse. Although they are invisible in white light, early observers could see them in the hydrogen alpha (Hα) emission line with a spectrograph and compared them to a “burning prairie.” Spicules are not connected with sunspots (sunspot) or plages and are also absent from the channels where solar prominences (solar prominence) appear.

Harold Zirin
 

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Universalium. 2010.

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Look at other dictionaries:

  • spicule — [ spikyl ] n. m. • 1830; lat. spiculum « dard » 1 ♦ Sc. nat. Structure animale, végétale ou minérale, en forme d épi ou de dard. Spécialt Chacun des petits bâtonnets calcaires ou siliceux constituant le squelette des éponges. 2 ♦ (1959) Astron.… …   Encyclopédie Universelle

  • spiculé — spiculé, ée (spi ku lé, lée) adj. Terme de botanique. Se dit de l épi composé de plusieurs épillets sessiles ou subsessiles serrés contre le rachis, par exemple l ivraie. ÉTYMOLOGIE    Spicule …   Dictionnaire de la Langue Française d'Émile Littré

  • spicule — 1785, from Fr. spicule, from dim. of L. spica (see SPIKE (Cf. spike) (n.1)) …   Etymology dictionary

  • Spicule — Spic ule, n. [L. spiculum a little point, a dart.] 1. A minute, slender granule, or point. [1913 Webster] 2. (Bot.) Same as {Spicula}. [1913 Webster] 3. (Zo[ o]l.) Any small calcareous or siliceous body found in the tissues of various… …   The Collaborative International Dictionary of English

  • spicule — [spik′yo͞ol΄] n. [< ModL & L: ModL spicula < ML, head of a lance or arrow < L spiculum, dim. of spica, a point, ear, SPIKE2] 1. Astron. any of the short lived, bright, dense gas jets continuously spurting up through the chromosphere of… …   English World dictionary

  • Spicule — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. Spicule signifie : élément ayant la forme d’une aiguille. Le sens diffère en fonction des circonstances : Spicule : en astronomie, un jet… …   Wikipédia en Français

  • Spicule — This article is about the skeletal structure. See also Spicule (solar physics) and Spicule (glass manufacture). Spicules are tiny spike like structures of diverse origin and function found in many organisms, such as the copulatory spicules of… …   Wikipedia

  • Spicule (solar physics) — In solar physics, a spicule is a dynamic jet of about 500km diameter on the Sun. It moves upwards at about 20 km/s from the photosphere. They were discovered in 1877 by Father Angelo Secchi of the Vatican Observatory in Rome. The chromosphere is… …   Wikipedia

  • Spicule (glass manufacture) — This article is about glass manufacture. See also Spicule (solar physics) and Spicule. Spicules are tiny glass flakes which are formed during the manufacture of glass vials. A glass tube is extruded at a constant rate and a jet of water applied… …   Wikipedia

  • Spicule (biologie) — Pour les articles homonymes, voir Spicule. spicules triactines d une éponge Le mot spicule est un terme générique qui regroupe les sécrétions minérales extr …   Wikipédia en Français

  • Spicule (astronomie) — Pour les articles homonymes, voir Spicule. Les spicules sont des jets de gaz éphémères s élevant à grande vitesse se trouvant dans la chromosphère (couche externe de gaz entourant le Soleil). C est Angelo Secchi qui découvre les spicules en 1877… …   Wikipédia en Français

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