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What causes the curved dark streak? Is this a region devoid of dust or perhaps a shadow cast from an out of plane dense dust jet ? (There does seem to be a corresponding bright streak to the left which could be the source of the shadow. Would this be consistent with the current geometry relative to the sun ?)
Robin
Robin,
The fact that the total magnitude of the expanding dust coma is constant implies that it must be optically thin, i.e. individual dust grains are not shadowing other dust grains. That tells us that this feature is not a shadow. It is much more likely to be caused by variations in the dust column along our line of sight caused by the outflow dynamics close to the nucleus when the outburst occurred. The outburst itself is a very rapid event where gas and dust leave the nucleus at high velocities and then expand into a vacuum. That process shapes the three dimensional outflows which we then see projected onto a 2D image.
Richard Miles is the real expert on this and this comet and 29P have been giving him a lot of data to work with.
Nick.
This latest outburst was a big one but it has had no detectable effect (so far) on the motion of the very massive nucleus of 12P. This plot shows astrometric residuals from three stations (970, I79 and I81) with an orbit fit that uses positions up to Nov 14. You can see that there is a large temporary displacement of the residuals on Nov 15 and 16. This is due to the biasing of the centroid of the coma by the very bright dust cloud moving NE from the nucleus. As this dust cloud fades the astrometry is returning to normal.
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