A Highly Collimated Jet from the Red Square Nebula, MWC 922
  Deep, narrow-band \Ha\ and 6584 \AA\ [\Nii ] CCD images of the peculiar,
infrared excess B[e] star MWC~922 reveal a collimated, bipolar jet orthogonal
to the previously detected extended nebula. The jet consists of a pair of
$\sim$0.15 pc segments on either side of MWC~922 separated by gaps. The most
distant jet segments disappear $\sim$0.6 pc from the star. The northwest beam
points to a faint emission-line feature 1.65 pc from MWC~922 that may be a
terminal bow shock where the jet rams the ambient medium. The narrow
opening-angle of the jet combined with an estimated internal sound speed of
$\sim$10 \kms\ implies a jet speed $\sim$500 \kms . The previously detected
nebula extends up to 0.6~pc to the southwest of MWC~922 at right angles to the
jet and appears to be an extension of the compact, edge-on disk surrounding the
star. It points toward the HII region Messier 16 located $\sim$1\degr\
($\sim$30 pc in projection) to the southwest. This nebula and jet appear to be
externally ionized by the ambient Lyman continuum radiation field and have
electron densities of n$_e \sim$ 50 to 100 cm$^{-3}$. The southwest nebula and
jet have similar surface brightness in \Ha\ and [\Nii ]. Faint 70 $\mu$m
emission traces the southwest ejecta that likely originates from $\sim$50 K
dust embedded in the photo-ionized plasma which may shadow the dimmer ejecta
northeast of MWC~922. MWC~922 may be a massive member of the Serpens OB1 or OB2
associations surrounding Messier 16 and Sh2-54.
