- (ASTRON) A short-lived (about
5 minutes), narrow jet of gas, less than 10,000 km long and 500 km in
diameter, in the upper chromosphere
of the Sun. Visible in the light of H-alpha,
spicules tend to cluster at the edges of supergranulation
cells and are usually seen as a mass of tiny brighter spike-like
features at the limb or as tiny darker spikes coming out of network
elements. Macrospicules are about 10 times larger and
are best seen in the He II ultraviolet line at 304 Å.
- (ZOOLOGY) A crystalline or mineral
deposit found in sponges, sea cucumbers, or
urochordates. Spicules are structural components in many sponges, and
may serve a protective function in other organisms.