Extraordinary, semistellar, line-emitting knots are apparent in images of the Crab Nebula which were obtained with the Goddard Fabry-Perot imager at the Michigan-Dartmouth-MIT Observatory. The knots are most prominent for [O III] λ5007 emission through a 5.3 Å (FWHM) bandpass centered at 5015.3 Å, with representative fluxes of roughly 10-14 ergs cm-2 s-1. They are aligned in arcs, seven to the north and four to the south, from the pulsar. The northern group appears to be in a bounded corridor through the filamentary structure. Measurements over a 2 year baseline yield proper motions of order 0″.1 yr-1, corresponding to transverse velocities of order 900 km s-1 for a distance of 1830 pc. The knots are characterized by remarkably strong [Ar III] emission, possibly indicating high argon abundances, high gas temperatures, or anomalous physical processes.
ISM: individual (Crab Nebula), Supernova remnants
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© The Authors
Macalpine, Gordon M.; Lawrence, Stephen S.; Brown, Beth A.; Uomoto, Alan; Woodgate, Bruce E.; Brown, Larry W.; Oliversen, Ronald J.; Lowenthal, James D.; and Liu, Charles, "Extraordinary Line-Emitting Knots in the Crab Nebula" (1994). Astronomy: Faculty Publications, Smith College, Northampton, MA.