Far-Flung Filaments of Ejecta in the Young Supernova Remnant G292.0+1.8

New optical images of the young supernova remnant (SNR) G292.0+1.8, obtained from the 0.9 m telescope at Cerro Tololo Inter-American Observatory, show a more extensive network of filaments than had been known previously. Filaments emitting in [O III] are distributed throughout much of the 8′ diameter shell seen in X-ray and radio images, including a few at the very outermost shell limits. In addition to the extensive [O III] filaments, we have detected four small complexes of filaments that show [S II] emission along with the oxygen lines. In a single long-slit spectrum we find variations of almost an order of magnitude in the relative strengths of oxygen and sulfur lines, which must result from abundance variations. None of the filaments, with or without [S II], shows any evidence for hydrogen, so all appear to be fragments of pure supernova ejecta. The [S II] filaments provide the first evidence for undiluted products of oxygen burning in the ejecta from the supernova that gave rise to G292.0+1.8. Some oxygen burning, either hydrostatic or explosive, must have occurred, but the paucity of [S II]-emitting filaments suggests that either the oxygen burning was not extensive or that most of its products have yet to be excited. Most of the outer filaments exhibit radial, pencil-like morphologies that suggest an origin as Rayleigh-Taylor fingers of ejecta, perhaps formed during the explosion. Simulations of core-collapse supernovae predict the development of such fingers, but these have never before been so clearly observed in a young SNR. Following careful subtraction of the stars in the field, we have measured the total flux in [O III] λ5007 as 5.4 × 10-12 ergs cm-2 s-1. Using a distance of 6 kpc and an extinction correction corresponding to E(B - V) = 0.6 mag (lower than previous values but more consistent both with our data and with X-ray and radio measurements of the hydrogen column density) leads to a luminosity of 1.6 × 1035 ergs s-1 in the 5007 Å line.