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.
A Star Is Born (Jay-Z song) were ultimately used in the final mix. Williams himself was not aware of the prominence of his vocals on "A Star Is Born" until his friend Omar Edwards approached him and complimented his performance on the song. "A Star Is Born" received mixed reviews from music critics. Charles Aaron of "Spin" praised its "anthemic, edgy soul-clap" beat and the two rappers' individual performances, lauding Jay-Z in particular as "effortlessly dazzling". "Pitchfork"s Ian Cohen, however, dismissed the song as a "numbingly non-committal salutation" Alexis Petridis, writing for "The Guardian", negatively described "A Star Is Born" as a "mass of indistinct tracks".