Shell star variables. Pleione and Gamma Cassiopeiae itself are both variable stars that have intermittent shell episodes where strong shell features appear in the spectrum and the brightness increases or decreases significantly. At other times the shell is not detectable in the spectrum, and even the emission lines may disappear. Shell star A shell star is a star having a spectrum that shows extremely broad absorption lines, plus some very narrow absorption lines. They typically also show some emission lines, usually from the Balmer series but occasionally of other lines. The broad absorption lines are due to rapid rotation of the photosphere,
Shell plating Shell plating Shell plating is the outer-most structure on the hull of a steel or aluminum ship or boat. A strake is the name given to each line of planking in a wooden vessel. In modern ship construction it refers to the longitudinal run of plating covering the hull, deck and bulkhead structure. Certain specific strakes are uniquely identified: Keel: is a special strake of the Bottom plating extending from the centerplane outboard. Bottom: the Bottom Shell plate strakes extend from the Keel to the Bilge. Bilge: is the plating which transitions from the more-or-less horizontal Bottom Shell to the