  We report the discovery of a spatially-resolved edge-on protoplanetary disk
in the ~2-Myr-old MBM 12 young association. Our near-infrared images of LkHa
263C (MBM 12A 3C), obtained with the Hokupa'a adaptive optics system on the
Gemini North telescope, clearly show two elongated reflection nebulosities
separated by a dark lane, a morphology well-matched by scattered light models
of an optically thick (at near-infrared wavelengths) edge-on disk. An optical
spectrum of the scattered light nebulosity obtained with the Keck II telescope
exhibits a spectral type of M0 +/- 0.5 (T_eff = 3850 +/- 100 K) for the central
star and contains H_alpha and forbidden emission lines, which may indicate the
presence of a jet. The absence of a near-infrared point source implies A_K >
9.5 toward the unseen central star. The disk is flared and has a radius of ~150
AU (at a distance of 275 pc) and an inclination of 87 degrees. The aspect ratio
of the model disk in the J-band is 0.72. There is possible evidence for dust
settling to the disk midplane. LkHa 263C is 4.115" from the 0.415" binary LkHa
263 A and B (MBM 12A 3A and 3B), which is itself 15.5" from LkHa 262 (MBM 12A
2). Thus, LkHa 263C may be the first disk to be clearly resolved around an
individual star in a young quadruple system. The detection of a faint edge-on
disk near a bright star demonstrates both the high angular resolution and the
high sensitivity that can be achieved with adaptive optics imaging on large
telescopes.
