  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 HII region NGC 3603. Near-infrared high resolution adaptive optics images
in the Br gamma line and HST/NICMOS images in the HeI 1.08mu line were compared
with iso-velocity maps in the H alpha and [NII] 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 [NII] lines trace the
entire silhouette of the hourglass. The bipolar lobes of the hourglass expand
at 70 km/s, whereas the ring around the waist of the hourglass expands at 30
km/s. Both the ring and the bipolar lobes have about the same dynamical age,
indicating a common origin and a major outburst and mass-loss event 6630 yr
ago. The ionized mass within the hourglass is between 0.3 Mo and 0.6 Mo - quite
comparable to the total mass suggested for the expanding (pre-supernova) shell
around SN 1987 A. The hourglass structure around Sher 25 is similar to that of
SN 1987 A in spatial extent, mass, and velocities. The major differences
between these two nebulae might arise from environmental effects. Both internal
and external ionization sources are available for Sher 25's nebula.
Furthermore, Sher 25 and its hourglass-shaped nebula appear to be moving to the
south-west with respect to the ambient interstellar medium, and ram pressure
has apparently deformed the hourglass. We conclude that the circumstellar
nebulae around SN 1987 A and Sher 25 are very similar and define a new class of
nebulae around blue supergiants in their final evolutionary stage.
