Re: OT: Comet 17 / P Holmes: Stokes Parameter polariztion difference image and Halpha

Richard Crisp

aligned particles of the right size relative to the wavelength of light will polarize light

you can get the same effect off the surface of a lake too

the flow can align the particles: both solar wind for the comet as a whole and the mass outflow from a jet: both can have the effect of aligning elongated particles more or less in the same orientation

here's a bit of info from a friend:

thanks to Dr. Liebrecht Venter for bringing this to my attention, I'd say that the polarization difference imaging method I used to photograph 17/P Holmes apparently is a useful diagnostic technique to probe the comet's composition

Polarization of Light Scattered by Cometary Dust Particles: Observations and Tentative Interpretations
Journal Space Science Reviews
Publisher Springer Netherlands
ISSN 0038-6308 (Print) 1572-9672 (Online)
Issue Volume 90, Numbers 1-2 / October, 1999
DOI 10.1023/A:1005250131509
Pages 163-168
Subject Collection Physics and Astronomy
SpringerLink Date Monday, October 25, 2004

A.-Chantal Levasseur-Regourd

Abstract Analysis of the polarization of light scattered by cometary particles reveals similarities amongst the phase curves, together with some clear differences: i) comets with a strong silicate emission feature present a high maximum in polarization, ii) the polarization is always slightly lower than the average in inner comae and stronger in jet-like structures. These results are in excellent agreement with the Greenberg model of dust particles built up of fluffy aggregates of much smaller grains. Also, they suggest the existence of different regions of formation, and of different stages of evolution for the scattering particles inside a given cometary coma.
Comets - Dust particles - Scattering - Polarization

----- Original Message -----
From: Rick Thurmond
To: ap-gto@...
Sent: Friday, October 26, 2007 6:29 PM
Subject: Re: [ap-gto] OT: Comet 17 / P Holmes: Stokes Parameter polariztion difference image and Halpha

Very interesting to see that jet. Why do you suppose the jet
polarizes the light? And would that jet show up on a doppler Halpha
image, if one could be made?


On Oct 25, 2007, at 6:42 24AM, Richard Crisp wrote:

> Halpha image: it is what I had handy at the moment:
> polarization difference image
> the jet is visible emanating from the core when viewed as a
> polarization
> difference color image
> quite interesting....
> be sure to look at the highest rez version

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