Abstract
THE Crab nebula, the remnant of the celebrated supernova of 1054 (refs 1, 2), lies 2 kpc from the Earth3,4 and is the most powerful neutron-star-driven nebulosity known. Its emission from radio to X-ray wavelengths is predominantly synchrotron radiation, with a power-law spectrum that steepens abruptly at 1013 and 1016 Hz (ref. 4). The infrared satellite observatory IRAS revealed significant excess emission, above the synchrotron spectrum, peaking between 60 and 100 μm in wavelength5. This was attributed to thermal radiation by dust with at least two characteristic temperatures in the range 40–100 K (refs 5,6). We have now reanalysed the IRAS data, taking care to remove contamination by background emission, and find that the revised infrared flux densities are in fact well explained by a single dust component at a temperature of 46 K. The required dust mass is 0.02 solar masses (M⊙), corresponding to a gas to dust ratio of 100:1. We also determine more accurately the break frequency, 1.4 × 1013 Hz, in the power-law spectrum. This value implies, for a steady-state synchrotron model, a time-averaged magnetic field of 420 μ,G, which is less than the value corresponding to an equipartition of energy between radiating particles and magnetic field, but probably greater than the present field strength.
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Strom, R., Greidanus, H. Evidence for single-temperature dust in the Crab nebula from a reanalysis of its infrared spectrum. Nature 358, 654–655 (1992). https://doi.org/10.1038/358654a0
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DOI: https://doi.org/10.1038/358654a0
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