  The formation of the highest mass stars are thought to be dominated by
instabilities resulting from gravitation and radiation. Instabilities due to
gravitation are commonly demonstrated by observations of fragmentation, but
those due to effects of radiation have thus far not been found. Here I report
on the NACO adaptive optics and mid-infrared diffraction-limited VISIR imaging
data of an extemely luminous ultra-compact HII region G333.6-0.2. Two infrared
sources, one bright in the near-infrared(appearing point-like) and another in
the mid-infrared (resolved with an elliptical shape) are uncovered through this
data, which are located at the heart of this region. These infrared sources
appear to be embedded in the waist of a bipolar-shaped nebula and UCHII region,
the lobes of which are separated by a dark patch. Dense filamentary features
with finger/hook morphology are found; they appear to be connected to the two
bright infrared sources and the sizes of these hook features are sharply
limited to <5000 AU. The observed properties of this target and a large amount
of previous data obtained from the literature are compared together with the
results of various numerical simulations of high-mass star formation. This
comparison favours the interpretation that the finger/hook-like structures
likely represent radiatively driven Rayleigh-Taylor instabilities arising in
the outflow cavity of a forming high-mass binary star system.
