GOODBYE TO POLARIS THE CEPHEID

New radial velocities and uvby photometry for Polaris are presented. T hese reveal that the pulsational amplitude of Polaris had declined to 0.59 +/- 0.19 km s-1 and 0.010 +/- 0.002 mag in V by 1992. Comparison with earlier determinations reveals an exponential change with time ra ther than any sudden onset of the decline, and suggests that Polaris h ad an amplitude near 0.12 mag (6.0 km s-1) prior to 1900. There is no sign of the amplitude changing in a manner consistent with a beat phen omenon; instead, the star seems destined to stop pulsating in 1994. Ou r data add new points to the O-C diagram of Polaris and show a continu ation of the period increase known previously. We point out that depar tures of this diagram from a true parabola do not necessarily imply th at factors other than stellar evolution are at work. Finally, we lay t o rest the myth that the amplitude of Polaris has declined because it is evolving across the red edge of the Cepheid instability strip. We s how Polaris to be well within the strip and surrounded there by Cephei ds of substantial amplitude. In particular, Polaris is virtually ident ical to RT Aur in M(V) and color, yet RT Aur has an amplitude of 0.8 m ag. We conclude that there is as yet no adequate understanding of what sets the amplitude of a Cepheid.