[meteorite-list] EPOXI images of Comet Hartley 2

[Chris Peterson]

Eric-

The Yarkovsky effect does not work by vaporizing material. It is related to 
the momentum of photons.

In the case of outgassing, the momentum is very low compared with the 
momentum of the nucleus, so the effect on the orbit is small as well. The 
Yarkovsky effect is also quite small on a body the size of Hartley. I think 
Yarkovsky dominates because it is a continuous process over the entire 
orbit, whereas outgassing only occurs during the time the nucleus is near 
the Sun. But in reality, both effects, as well as others (like gravitational 
perturbation) produce an orbit that can't be accurately predicted too far 
into the future. It is important to regularly recalculate orbital elements 
for bodies like this if very precise position information is required. I 
noticed during the flyby this morning that there seemed to be a 
miscalculated close passage time, which was corrected by a few minutes when 
the comet's orbit was recalculated.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "Meteorites USA" <eric at meteoritesusa.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Thursday, November 04, 2010 10:35 AM
Subject: Re: [meteorite-list] EPOXI images of Comet Hartley 2


> Hi Gary, Your explanation of the outgassing of comets and Count Deiro's 
> question, made me think of one of the proposed ways of deflecting 
> asteroids which uses the Yarkovsky effect to focus the suns energy on the 
> outer surface of the asteroid thereby vaporizing material and causing a 
> propulsive force to nudge the asteroid into a new orbit.
>
> So, if the Yarkovsky effect will work on asteroids, what's the difference 
> between that, and Comet Hartley 2's outgassing on the orbit of the body? 
> Is the force from the outgassing that much less than what the Yarkovsky 
> effect could produce?
>
> Regards,
> Eric