A Symmetric Bipolar Nebula Around MWC 922
P. G. Tuthill1* and
J. P. Lloyd2
We report regular and symmetric structure around dust-enshrouded
Be star MWC 922 obtained with infrared imaging. Biconical lobes
that appear nearly square in aspect, forming this "Red Square"
nebula, are crossed by a series of rungs that terminate in bright
knots or "vortices," and an equatorial dark band crossing the
core delimits twin hyperbolic arcs. The intricate yet cleanly
constructed forms that comprise the skeleton of the object argue
for minimal perturbation from global turbulent or chaotic effects.
We also report the presence of a linear comb structure, which
may arise from optically projected shadows of a periodic feature
in the inner regions, such as corrugations in the rim of a circumstellar
disk. The sequence of nested polar rings draws comparison with
the triple-ring system seen around the only naked-eye supernova
in recent history: SN1987A.
2 Department of Astronomy, Cornell University, Ithaca, NY 14853, USA.
* To whom correspondence should be addressed. E-mail: p.tuthill{at}physics.usyd.edu.au
