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see chromospherechromosphere
[Gr.,=color sphere], layer of rarefied, transparent gases in the solar atmosphere; it measures 6,000 mi (9,700 km) in thickness and lies between the photosphere (the sun's visible surface) and the corona (its outer atmosphere).
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Spicules are spike-like prominences visible at the limb of the sun during solar eclipses or during observation of the sun in monochromatic light, for example, the light of the hydrogen line Hλ. They extend into the solar corona to heights of 6,000–10,000 km and have diameters of 200–2,000 km. The average lifetime of a spicule is 5–7 min. Spicules move upward at speeds of 20–30 km/sec; the speeds of internal movements are 5–10 km/sec. The temperature of a spicule is approximately 8000°K in the lower part and about 16,000°K in the upper part. The density of spicules varies with height from 2 × 1011 to 3 × 1010 atoms/cm3. Hundreds of thousands of spicules exist on the sun at one time. They arise primarily at the edges of the cells of the chromospheric network.



(1) In certain invertebrates a skeletal element consisting of calcium carbonate or, less commonly, silica (silicon dioxide). Spicules occur in sponges (in the form of one-, three-, four-, and many-rayed needles), octocorallians, aplacophorans, mollusks, holothurians and other echinoderms (in the form of small wheels, anchors, or lattices), and ascidians (in the form of thorny spheres).

(2) In nematodes, a part of the male copulatory organ. In some species the spicules are supplementary formations; they protrude from the cloacal opening of the male and serve to widen the female’s vagina. In other species sulcate spicules come together and conduct the spermatozoa into the vagina of the female.


One of an irregular distribution of jets shooting up from the sun's chromosphere. Also known as solar spicule.
An empty diatom shell.
(invertebrate zoology)
A calcareous or siliceous, usually spikelike supporting structure in many invertebrates, particularly in sponges and alcyonarians.
References in periodicals archive ?
Radix fibrosa, flexuosa, pallida; culmi caespitosi, paucinodes, nodis angustis fuseis glabris; rhachis eximie articulata, articulis cuneiformibus apice oblique excavatis margine ciliatis; spiculae in axi articulato barbato geminae, terminales ternae; altera subbiflora hermaphrodita sessili, altera neutra pedicellata; glumae duae, inferior mutica, superior setigera.
The Silurian part of the section seems to contain a more abundant and diverse fossil assemblage, including in addition to the microfossils listed above also 1-4 fragments of graptolites, ostracodes, inarticulate brachiopods and some sponge spiculae.
5 mm SL in only known female, having short legs (C/SL = 33 %); a hand phalangeal formula 2-2-3-3, the entire auditory apparatus apparently absent, and the dorsum with few spiculae or coni but with black, gray tipped coni on the side of the head, upper surfaces of the upper limbs, and flanks.