Jim Thanks for explaining that. Word around the office is that the other tail is a contrail from a mohter ship hiding behind the comet. Yours sound more likely but not as titillating. Jim Jim Cobb <james@cobb.name> wrote: I believe that one is the dust tail and the other is the plasma tail. It is not uncommon for a comet to have two tails. The angular separation between the tails is unusually large. I believe this is caused by the unusual geometry of the comet at its closest earth approach. Typically a bright comet has perihelion considerably closer to the sun than the earth's orbit. For this one, the perihelion (which occurs Jan 24) has distance to the sun of 1.2 AU. For the closest earth approach (which occurred Jan 5) it had a distance to the sun of 1.24 AU, and distance to earth of 0.347 AU. Since the tails stream "basically away from the sun", we are looking at them from extreme perspective. I believe this is the source of the large angular difference between the two tails. This was all figured out from playing with xephem. I can supply figures to anyone who may be interested. Jim ---- Jim Cobb james@cobb.name On Jan 10, 2005, at 8:16 AM, Jim Gibson wrote:
Can anyone explain why there appears to be 2 tails in the animation that Rich posted?
Jim
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