[BAA Comets] Post-perihelion fragmentation of 168P/Hergenrother

[denis buczynski]

Hi Richard,
Thanks for the comments below. It is very beneficial to us to be able to access the images taken by 
the Foulkes Telescopes for the schools programme which allow us to see in detail the progression of 
this fragmentation process. As you say it is probably unlikely that we(amateurs) will be able to 
image this fragment now that it is fading.I suppose it is not surprising that the fading is 
occurring, partly due to the increasing distance from earth and also that the fragment must have 
parted from the main body at its surface and will subsequently lose its volatiles and material quite 
quickly without any replenishment. I see from the Foulkes image that there is still quite a lot of 
material flowing down the tail ( as also seen in Nick James's image from last night) so I suppose 
that there may be a chance of more large fragments appearing. However now that perihelion passage is 
in the past now I suppose that there are not the same extreme forces acting on the comet and that it 
will probably return to is quiescent state soon. Do you think that the fragmentation we have 
witnessed was the cause of the brightness outburst seen over the past month? This has been a 
fascinating comet to observe and has been so well placed in high northerly declinations, we have 
been very lucky that so many observations have been possible. This comet apparition reinforces the 
age old advice that comets are unpredictable objects and we should never be surprised when one 
behaves unexpectedly.
Denis Buczynski

-----Original Message----- 
From: Richard Miles
Sent: Friday, November 02, 2012 12:31 PM
To: BAA Comets discussion list
Subject: Re: [BAA Comets] Post-perihelion fragmentation of 168P/Hergenrother

Thanks Denis for trying to detect the fragment.  It turns out that it has
faded quite a bit and is still only about 3.3" from the main nucleus.

This morning two schools/colleges (Queen's College and Dollar Academy)
working with the Faulkes Team coordinated by Nick Howes each managed to
image the comet continuously for about 50 minutes using the Faulkes
Telescope North.  I downloaded their images and processed 19 of them using
the same approach as previous.  (The first few images were contaminated by a
nearby star so I did not use those.)  The results can be seen at:
http://www.britastro.org/~rmiles/Documents/168P_2012Nov02.png

The 'fragment' is now sporting a small tail of its own and is really very
faint compared to the main nucleus, most of the light from which has been
removed by the rotational gradient image processing.

For comparison the earlier images are available at:
http://www.britastro.org/~rmiles/Documents/168P_20121022-26.png

The apparent drift rate of the fragment relative to the main nucleus is very
slow.  This is in part caused by the increasing delta distance over recent
days, so although the actual separation in km is increasing, the mini-comet
appears to remain hugging the parent body.  In 6 days the separation has
maybe gone from 2.4" to 3.3".  Compounding the problem for amateur-size
telescopes appears to be that the fragment has faded significantly so may be
starting to break-up - hard to tell at this stage.

Richard Miles
Director, Asteroids and Remote Planets Section
British Astronomical Association

----- Original Message ----- 
From: "denis buczynski" <buczynski8166 at btinternet.com>
To: "BAA Comets discussion list" <comets-disc at britastro.org>
Sent: Friday, November 02, 2012 12:06 PM
Subject: Re: [BAA Comets] Post-perihelion fragmentation of 168P/Hergenrother


>I was also able to image this comet last night, in a dark sky (first with
>moon out of sky for some
> time) and took a set of 20x30s in r band filter to see if the reported
> fragmentation was visible yet
> at 2"/pixel resolution I use with my C14/ST9XE combination. I could not
> detect any fragment with the
> processing I used (stacking and log stretch). I wonder if a drift rate can
> be calculated fro the
> fragment from the large telescope images which would give us an indication
> when it should be
> possible for observers using the size of telescope we employ to image the
> main fragment? I will
> continue to image this active comet. I have placed all the images
> submitted to the Comet Section on
> the Comet Gallery on the BAA Website.
> Direct links to the images I took last night are at:
>
> http://britastro.org/baa/index.php?view=detail&id=646&option=com_joomgallery&Itemid=200
>
>
> http://britastro.org/baa/index.php?view=detail&id=645&option=com_joomgallery&Itemid=200
>
>
> Denis Buczynski
> Secretary Comet Section
> British Astronomical Association
>
> -----Original Message----- 
> From: Nick James
> Sent: Friday, November 02, 2012 7:49 AM
> To: BAA Comets discussion list
> Subject: Re: [BAA Comets] Post-perihelion fragmentation of
> 168P/Hergenrother
>
> I had a good opportunity to take some images of 168P last night in
> transparent skies using the relatively small (C11) telescope in my back
> garden. It is interesting to compare the results with those obtained
> with much larger telescopes.
>
> The resulting image is here:
>
> http://www.nickdjames.com/Comets/168p_20121101_ndj.jpg
>
> FWHM was 3".5 which is not bad for here but doesn't really compare well
> to the 1".5 or less using the bigger scopes on mountains. There's no
> sign of the fragment (as expected at this resolution) but the rotational
> gradient does show flow down the near tail.
>
> This is definitely a comet that is worth keeping under observation.
>
> Nick.

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