granule(redirected from Birbeck granules)
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granule,in astronomy: see photospherephotosphere,
luminous, apparently opaque layer of gases that forms the visible surface of the sun or any other star. The photosphere lies between the dense interior gases and the more attenuated gases of the chromosphere.
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A convective cell in the solar photosphere, about 600 miles (1000 kilometers) in diameter.
A somewhat rounded rock fragment ranging in diameter from 2 to 4 millimeters; larger than a coarse sand grain and smaller than a pebble.
Geology a single rock fragment in gravel, smaller than a pebble but larger than a sand grain