🚀 go-pugleaf

I just ran the Swift-Tuttle orbital elements through the Voyager Mac
Planetarium program.  Lock on the earth, zoom in to see the Moon and watch
the comet race by.  Very impressive if completely misleading (no forces).
One thing to note: the time of perihelion passage in the IAU orbital elements
needs to be ``tuned'', otherwise the comet crosses the Earth's orbit while
we're quite far away.  I arbitrarily changed if from 12/12.323/92 to 7/21/91
to increase the perceived threat (to keep my Astronomy class alert tomorrow!).
This delay is along the lines suggested in article 92Oct27151516@topaz.ucsc.edu,
steinly@topaz.ucsc.edu (Steinn Sigurdsson) who writes:
>No, the delay is along the orbit, perturbations orthogonal to
>the orbit are small, basically there is an uncertainty in the
>aphelion and small outgassing at perihelion is effective in
>shifting the period due to changes in the aphelion - note the limit
>as eccentricity approaches 1 infinitesimal changes in perihelion
>velocity can produce arbitary changes in period but not in
>the nodes.
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Gerald Cecil cecil@wrath.physics.unc.edu  919-962-7169 
Physics & Astronomy, U of North Carolina, Chapel Hill, NC 27599-3255 USA