Shell star 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, the emission lines from an equatorial disk, and the narrow absorption lines are produced when the disc is seen nearly edge-on. Shell stars have spectral types O7.5 to F5, with rotation velocities of 200–300 km/s, not far from the point when the rotational acceleration would disrupt the star.
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