A narrow, almost vertical, band on the right hand side of the
→ main sequence in the → H-R diagram
occupied by many different types of → pulsating stars
(→ RR Lyrae, → Cepheids,
→ W Virginis, → ZZ Ceti).
Stars traverse this region at least once after they leave the main sequence.
The narrow temperature range of the instability strip
corresponds to the stellar → effective temperature that can sustain
→ partial ionization zones, capable of maintaining
stellar oscillations. The blue (hot) edge of the instability strip pertains to stars
with surface temperatures hotter than ~ 7500 K. Because these stars have
partial ionization zones too close to their surface, the pulsation mechanism is not
active. The red (cooler) edge of the instability strip is determined by stars
with a temperature lower than ~ 5500 K. In these stars convection prevents
the build-up of heat
pressure necessary to drive pulsations.
See also: → instability; → strip.
