We have performed a detailed study of the morphology and kinematics of
the hourglass-shaped nebula around the blue supergiant Sher 25 in the
galactic giant H II region NGC 3603. Near-infrared high-resolution ad
aptive optics images in the Br gamma line and HST/NICMOS images in the
He I 1.08 mu m line were compared with isovelocity maps in the H alph
a and [N II] lines. The adaptive optics observations clearly resolved
the width of the ring (0.'' 9, i.e., 0.027 pc), yielding delta R/R = 1
/8. We show that the H alpha and [N II] lines trace the entire silhoue
tte of the hourglass, The bipolar lobes of the hourglass expand at 70
km s(-1), whereas the ring around the waist of the hourglass expands a
t 30 km s(-1). Both the ring and the bipolar lobes have about the same
dynamical age, indicating a common origin and a major outburst and ma
ss-loss event 6630 yr ago. The ionized mass within the hourglass is be
tween 0.3 and 0.6 M.-quite comparable to the total mass suggested for
the expanding (presupernova) shell around SN 1987A. The hourglass stru
cture around Sher 25 is similar to that of SN 1987A in spatial extent,
mass, and velocity. The major differences between these two nebulae m
ight arise from environmental effects. Both internal and external ioni
zation sources are available for Sher 25's nebula. Furthermore, Sher 2
5 and its hourglass-shaped nebula appear to be moving to the southwest
with respect to the ambient interstellar medium, and ram pressure has
apparently deformed the hourglass. We conclude that the circumstellar
nebulae around SN 1987A and Sher 25 are very similar and define a new
class of nebulae around blue supergiants in their final evolutionary
stage.