[BAA Comets] Two outbursts of Comet 29P/S-W1 in quick succession

[Richard Miles]

Yes indeed, Denis.

Now, some answers to your questions:

1. Now that there is more continous monitoring, do you think that outbursts 
are more numerous and happen more often than was previously thought?

=> Yes, we are seeing more faint ones only because of the intensive 
monitoring, which really began in 2014 January. One early finding was the 
existence of mini-outbursts, which involve brightness increases of <1.0 mag. 
There looks to be a lower limit on outburst amplitudes in that because the 
nucleus is large (~60km across) it has an appreciable gravity, which means 
that material from the weakest outbursts tends to fall back onto the 
nucleus. The lowest amplitude event appears to be 0.35 mag or so.

2. Could it be that this comet is in a more or less in a permanent state of 
outburst or enhanced activity?

=> Generally speaking, yes, in that (since early 2014) the longest interval 
the nucleus has been observed remaining dormant between outbursts is only 
about 70 days, at which point the coma had dispersed to a large extent. 
However, of late such an occurence has been relatively rare.

3. Comets, fascinating objects eh?

=> I do believe we are especially lucky to have 29P performing as it does. 
It was likely a volatiles-rich TNO of significant size that migrated inwards 
and became trapped between Jupiter and Saturn. It's rotation rate of ~57-58 
days appears to be amongst the very slowest of all solar system bodies and 
this accentuates its unique behaviour. BTW, the other 'special' phenomenon 
we are lucky to be treated to is that of the family of Kreutz Sungrazers, 
thanks to the chance, very close perihelion passage of some very large comet 
many centuries ago.

Note to list members:  As one purpose of this group is to engage in 
discussions on the subject of comets, if other folk on the list would like 
to contribute in some way then please do feel free to do so. The most basic 
questions are often the most challenging!

Cheers,
Richard


----- Original Message ----- 
From: "denis buczynski" <buczynski8166 at btinternet.com>
To: "BAA Comets discussion list" <comets-disc at lists.britastro.org>
Sent: Wednesday, June 28, 2017 5:35 PM
Subject: Re: [BAA Comets] Two outbursts of Comet 29P/S-W1 in quick 
succession


> Hi Richard,Very interesting and well done to the observers who have picked 
> up this latest outburst. Now that there is more continous monitoring, do 
> you think that outbursts are more numerous and happen more often that was 
> previously thought? Could it be that this comet is in a more or less 
> permanent state of outburst or enhanced activity.Comets, fascinating 
> objects eh?Denis Buczynski
>
>
>      From: Richard Miles <rmiles.btee at btinternet.com>
> To: BAA Comets discussion list <comets-disc at lists.britastro.org>
> Cc: Observadores_cometas at yahoogroups.com; comets-ml at yahoogroups.com
> Sent: Wednesday, 28 June 2017, 18:11
> Subject: [BAA Comets] Two outbursts of Comet 29P/S-W1 in quick succession
>
> Comet 29P has outburst again, just 5.5 days or so since its last outburst.
> First detected by Jean-Francois Soulier (A. Maury, J.-B. de Vanssay) from
> SpaceObs (W96), Chile:
>
> 0029P C2017 06 27.45029 21 40 09.67 -13 19 24.1 16.27N F65
> 0029P C2017 06 28.19032 21 40 00.14 -13 19 30.1 15.21N W96
>
> Date of outburst: 2017 06 27.82 +/-0.30
>
> European observers may have caught the outburst a little earlier than
> Jean-Francois on the night of June 27/28.
>
> There have now been 5 outbursts during the present apparition.
> Interestingly, this one has taken place 116 days since the first outburst 
> of
> this observing season. That equates to exactly 2.00 solar days on the
> nucleus according to my calculations. It also appears that the present 
> event
> may have been triggered by that of June 22.32 +/-0.18.
>
> We shall now have to see if the outburst coma develops in a similar way to
> that of the first event (March 04).
>
> Richard Miles
> BAA
>
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