  We have discovered an axially symmetric, well-defined shell of material in
the constellation of Cepheus, based on imaging acquired as part of the Galactic
First Look Survey with the Spitzer Space Telescope. The 86'' x 75'' object
exhibits brightened limbs on the minor axis, and is clearly visible at 24
microns, but is not detected in the 3.6, 4.5, 5.8, 8.0, 70, or 160 micron
images. Followup with 7.5 - 40 micron spectroscopy reveals the shell to be
composed entirely of ionized gas, and that the 24 micron imaging traces solely
[O IV] 25.89 micron emission. The spectrum also exhibits weaker [Ne III], [S
III], and very weak [Ne V] emission. No emission from warm dust is detected.
Spectral cuts through the center of the shell and at the northern limb are
highly consistent with each other. The progenitor is not readily identified,
but with scaling arguments and comparison to well-known examples of evolved
stellar objects, we find the observations to be most straightforward to
interpret in terms of a young supernova remnant located at a distance of at
least 10 kpc, some 400 pc above the Galactic disk. If confirmed, this would be
the first SNR discovered initially at infrared wavelengths.
