Spectroscopy of a young brown dwarf in the rho Ophiuchi cluster

We present observations of a young (similar to 3-10 Myr old) brown dwarf within the rho Ophiuchi star-forming region. A low-resolution optical spectrum exhibits a spectral type of M8.5 +/- 0.5 and strong H alpha emission (W lambda similar to 60 Angstrom). After demonstrating the youth of this source through several additional lines of evidence, we place it on the H-R diagram and use the latest evolutionary tracks to derive a substellar mass of 0.01-0.06 M.. A more accurate mass estimate will require tests of the evolutionary tracks and temperature scales at such young ages and late types.