[BAA Comets] Outbursts of comets 29P and 17P (was 29P outburst ?)

Thu Jun 13 17:38:32 BST 2013

Jean-François,

Thanks for these contributions.

Yes, I am a member of the French comet list to which I see that many 
advanced comet observers contribute.

The abstracts submitted to the 2013 European Planetary Science Congress will 
be available to the public from June 27.  See:
http://www.epsc2013.eu/information/deadlines_and_milestones.html

Last year George Faillace and I published a theoretical paper outlining the 
various environments in which liquids can form beneath the surface of a 
cometary nucleus. See:
http://adsabs.harvard.edu/abs/2012Icar..219..567M

We now have sufficient observational material and information on chemical 
properties of key compounds at low temperatures to write papers linking the 
observational evidence to our hypotheses.  The intention is to submit draft 
papers on 29P (and 17P) for publication prior to EPSC 2013.

What I can say at this point is that cometary nuclei which rotate very 
slowly will be more prone to undergo periodic outbursts. And that CO is the 
volatile material which primarily drives outbursts of 29P, whereas CO2 is 
likely to be the main driver in the case of 17P. In both of these comets, 
different ices in the subsurface undergo premelting / melting and it is this 
solid-liquid phase change which underlies their strange behaviour. One 
crucial aspect of this "wetted layer" mechanism involves certain 
"nyctogenic" processes which only occur on the night-side of the nucleus and 
are a consequence of the nucleus lacking any significant atmosphere along 
with the microporous nature of the cometary regolith.

I should point out that I have coined the descriptor "nyctogenic" as a new 
word in the dictionary aimed at drawing attention to the special nature of 
some cometary nuclei when subjected to day-time heating and especially to 
night-time cooling.

Hope this is sufficient background information at this stage.

Richard Miles
BAA

----- Original Message ----- 
From: "Soulier Jean-FranÃ§ois" <jeffcomete at yahoo.com>
To: <comets-ml at yahoogroups.com>
Sent: Thursday, June 13, 2013 1:18 PM
Subject: Re: [comets-ml] 29P outburst ?

Good morning.

With all my sincere thanks for your observations and comments on 29P 
returns.

Here is the exact time of the first purchase made on this subject: 
20130613.00916.

Registration on 15x60s, an outgrowth of the coma is visible in S/E and 
increasing thresholds with
the application of a log. moderate, the coma to a size of 25" and 26" (+/- 
4").

http://6888comete.free.fr/images/forum/29PFC.jpg

http://6888comete.free.fr/images/forum/29PHC.jpg

It is interesting to note that this burst is well located in temporal level 
and therefore,
by its very nature shine remarkable fast.

There are regular debate on the French comet list on this comet.
http://fr.dir.groups.yahoo.com/group/les_cometes/

According to your information, there would be a relationship between 
rotation and outburst ?
Recurrent deep fault that the exposure of the season of the comet be 
producing CO2-CO volatile ?
Do you after your presentation to provide your findings about it in an 
article available for the community ?

If time permits there will undoubtedly be interesting to make measurements 
filtered for Af(rho).

Sincerely.
SOULIER Jean-François
C10/France
http://6888comete.free.fr/fr/Observerofcomets.htm

________________________________
De : Richard Miles <rmiles.btee at btinternet.com>
À : comets-ml at yahoogroups.com
Cc : BAA Comets discussion list <comets-disc at britastro.org>
Envoyé le : Jeudi 13 juin 2013 12h15
Objet : Re: [comets-ml] 29P outburst ?

Dear Jean-Francois, Clay et al.,

Yes, indeed. A number of amateurs keep close watch on this object. I
observed 29P on June 11.35 through cloud using the Faulkes Telescope North
and found it to be fainter than 16.0R. Can you indicate the exact time of
your pre-outburst observation of June 12 as it would be nice to fix a
relatively exact time for the start of the present outburst? Thanks.

I should mention that I have developed a model of this comet's nucleus and
thereby a possible explanation of its behaviour. Abstracts have been
submitted to the forthcoming European Planetary Science Congress (September
8 - 13, London): one an oral presentation entitled, "Microporosity, the
wetted layer and the role of CO and CO2 driving the activity of comets
29P/Schwassmann-Wachmann and 17P/Holmes", and a second as a poster
presentation with my colleague George Faillace, entitled, "Microporosity,
the "wetted layer" and the postulated outburst mechanisms driving the
activity of comets 29P/Schwassmann-Wachmann and 17P/Holmes".

I might also add that on April 19, I am on record as predicting another
outburst of 29P on June 14 (+/-5 day). That it has outburst virtually on cue
is one thing and may just be a chance coincidence, but what will be
important now is to monitor the nature of the expanding outflows of material
in the inner coma. The hypothesis I am working on for this prediction is
that at any one time there are very few active regions on the nucleus
involved in outbursts and that the present outburst originates from the same
site which produced the recent (weaker) April 14 outburst: the difference in
time of 59 days being associated with an approx. 60-day rotation period for
the nucleus. If the form of the outflows of material seen this time for 29P
are broadly similar to the April 14 event then the point will be finally
proven. I say this as our data has shown this characteristic behaviour
already occurred in 2010, 2011 and in 2012.

BTW: The way in which an outburst appears to strip away the existing
nebulosity around the nucleus, which Clay comments on below, I have also
noted in the past. Whether this is real or a contrast effect needs working
on further.

Finally, observations of 29P on June 13.32 made by Maui Community College
using the FT North (1.1" seeing) show the comet as essentially stellar in
appearance and magnitude 13.0R.

Richard Miles
British Astronomical Association

P.S. Have just seen that Josep M. Bosch has posted a report for 29P that on
June 12.88 the comet was magnitude 16.4R so the time of the present outburst
must be June 12.94 +/-0.05. Nice result.

----- Original Message ----- 
From: "P. Clay Sherrod" <mailto:drclay%40tcworks.net>
To: <mailto:comets-ml%40yahoogroups.com>
Sent: Thursday, June 13, 2013 3:31 AM
Subject: Re: [comets-ml] 29P outburst ?

> Yes, we confirm here at Arkansas Sky Observatories ASO/H45.
> A remarkable and surprising 24-hour outburst from magnitude 16.1 (m2) on
> June 12 UT
> to its present magnitude 13.2 (m1) tonight.
> In addition the comet has a remarkable transition in morphology from last
> night, with
> an outer irregular perimeter of nebulosity surrounding a stellar nucleus
> to a very
> large and dense coma/nuclear center measuring 15" arc across with a sharp
> perimeter
> and very little outer nebulosity (very faint to E and South of core).
>
> The comet once again shows that it deserves to be monitored regularly,
> often and
> carefully.
>
> This is a quite substantial outburst.
>
> Dr. Clay
> _____
> Arkansas Sky Observatories
> MPC H45 - Petit Jean Mountain South
> MPC H41 - Petit Jean Mountain
> MPC H43 - Conway West
> http://www.arksky.org/
>
> ----- Original Message ----- 
> From: "Soulier Jean-FranÃ§ois" <mailto:jeffcomete%40yahoo.com>
> To: <mailto:comets-ml%40yahoogroups.com>
> Sent: Wednesday, June 12, 2013 8:50 PM
> Subject: [comets-ml] 29P outburst ?
>
>
> Good evening.
>
> 29P S-W1 seems to be outburst ...
> Around +3 mag. compared with measurements made by the François Kugel
> 20130610.88 :
> http://comet.observations.free.fr/display-obs1.php?Num=9609
>
> measures :
> NET UCAC-4
> 0029P C2013 06 13.00951 13 35 42.06 -21 13 33.4 13.2 N
> 0029P C2013 06 13.02021 13 35 41.96 -21 13 32.0 13.1 N
> 0029P C2013 06 13.03167 13 35 41.87 -21 13 30.6 13.1 N
> ----- End -----
>
> 29P field :
> http://6888comete.free.fr/images/forum/29P20130613.jpg
>
> DSS :
> http://6888comete.free.fr/images/forum/DSS29P.jpg
>
> Thank you to confirm this observation ...
>
> Sincerely.
> SOULIER Jean-François
> C10/France