:: pats NP indulgently on the head ::
And that brings us to the subject of alien anal probing…
No, it’s Urmomsanus.
In a jar on your desk?
That’s a heart, per original source. 
Interestingly enough, even while much smaller and probably insignificant compared to other factors like the impact of the solar wind etc…even a comet will have some acceleration due to the differential and black body radiation.
But mostly I wanted ask if anyone had a cite to a simple model on what the effects of an idealized comet out-gassing are, which would obviously require some assumptions about how it tumbled, thus the reason I am asking for a simplified model.
As most of this out-gassing, in a spherical, non rotating comet would be at the perihelion, and because the out-gassing would have a vector that is radially outward with a component slightly to the rear.
The radially outward force would seem to circularize, and the delay in heating would seem to push in the prograde direction. If the solar wind was ignored, would the orbit slightly circularize or time or would the aphelion go higher due to the efficiencies of adding energy at the perihelion?
I never had a reason to look at orbital mechanics in this case, but for other readers things get weird:
If you throw an object “down” from the IIS, it will end up in a slightly more eccentric orbit that will be cycle between above and below your orbit. You have to toss it backwards at a high enough rate of speed if you want the object to reach the earth (ignoring long term drag at low earth orbit). And in fact an object ejected down is at risk of hitting you in the future!!
I can do the math if someone doesn’t have a quick answer, but it would seem that this would have a circularizing effect given enough time, and if the loss of mass wasn’t a problem. (once again ignoring solar winds etc…)
Roughly speaking, everything is circularizing in the long term, but comets often don’t even have a long term. Many comets are in hyperbolic orbits to begin with, and so will only pass by the Sun once, and even a comet that started in a closed orbit might be perturbed into a hyperbolic one by perihelion outgassing (at perihelion, a little perturbation will go a long way).