(meteorobs) Potential gamma-Delphinids return, June 2013

Sun Apr 28 10:42:53 EDT 2013

Thank you Roberto !

You probably mean the possible encounter of last year.
The possible encounter now is at about the extreme of one "wave" of the 
trail movements. And (the situation was near this also last year) this 
was calculated to be at the nominal distance of 0.0036 au, last year in 
June 11.  at 04:24 UT, ( in this year at 0.0021 au at 08:28 UT. So,  
this year would be more favorable, but if this was well observed last 
year and nothing seen, would probably tell that no outburst will happen 
even now.  The difference in the miss-distance is not bigg although 
these long period 1-r trails seem to be quite narrow and there is a 
clear difference in the predictions. That dfference might mean something 
like a threefold difference in the ZHR´s.  So, one can try to judge from 
these things if anything may appear now, or not.

Actually I do nto know of how much this may have been tried to observe 
last year.

Esko

> On Sun, 28 Apr 2013 11:31:13 +0000
>  Esko Lyytinen <esko.lyytinen at jippii.fi> wrote:
>>
>> Dear Karl and others,
>>
>> The possibility of an outburst from this was originally predicted in 
>> this paper:
>> http://adsabs.harvard.edu/abs/2003Icar..162..443L
>> http://www.sciencedirect.com/science/article/pii/S0019103502000714
>> This could earlier be freely downloaded, but maybe not any more. A 
>> earlier (working) link that I tested now, did not work.
>>
>> The theory behind this is discussed in this paper and there are also 
>> given some quite certain predictions and some quite uncertain.
>>
>> The main assumptions in this (case and similar to the others) are 
>> that the outburst in 1930 was real and secondly that it was from a 
>> 1-revolution dust trail of a long period comet ( which practically do 
>> not make definite outbursts other than from 1-rev. trail). And 
>> thirdly this is based on the derived radiant ( in case of not known 
>> parent comet as in this case).
>> In this we consider a long period comet to be one with the orbital 
>> period from a few hundreds years (like the Lyrids) to a few thousands 
>> years something like with the Aurigids. (Longer than a few thousand 
>> years will probably have the dust tails too much stretched adn 
>> consequently have a  too small density of meteoroids, (unless of 
>> especially big comet)).
>>
>> In principle this (the theory) is about similar to the 2007 predicted 
>> ( and observed) Aurigids outburts and some observed and post 
>> predicted Lyrids ourbursts. The parent comet of these are however 
>> known. The alpha Monocerotids parent comet is not known, but all the 
>> observed outbursts can be post-predicted or linked mutually. Actually 
>> the latest of these in 1995 was predicted beforehand (by Jenniskens) 
>> by means of a more
>> approximate treatment by means of the Solar system barycentre (see 
>> also below near the end).
>> With actual computer calculations also the timings can be linked to 
>> each other with an accuracy of about 15 minutes ( I recall). This AMO 
>> post prediction however has the radiant very accurately known from 
>> the 1995 video observations.
>> In practically any (without known parent orbit) case (if we do not 
>> have enough of diverse observations from several outbursts) one can 
>> not tell if the encouter was very central or not and these 
>> calculations have been made by assuming that they were central.
>>
>> As to the gamma-Delphinids, I read in that paper:
>> "The remaining six showers, the a-Lyncids (aLy), the
>> a-Pyxisids (aPx), the o-Orionids (oOr), the e-Eridanids (eEr), the 
>> g-Delphinids (gDe), and the a-Circinids (aCi) are less well 
>> documented (Jenniskens 1995, Jenniskens et al. 1997). Future returns 
>> need to establish that these are indeed long-period comet dust trail 
>> encounters."
>>
>> Then further:
>> "The first complication is that possible errors in the reported 
>> radiant position can introduce large variations in the calculated 
>> trail positions because of relatively close encounters with one of 
>> the big planets."
>>
>> This latest is a general remark, not specially for the gamma 
>> Delphinds. A sensitiviy test was amde for each of these by shifting 
>> the radiant about 5 degrees in declination and also (in another 
>> calculation) in the RA direction.
>> And this case fortunately seems to be relatively non-sensitve for 
>> errors in the radiant.
>> An error of about 10 degrees (to any direction) in the radiant, does 
>> not seem to nullify the prediction.
>> Now the nominal rD-rE distance is +0.00021 au, quite good.
>>
>> As a conclusion. IF the 1930 outburts was real and IF the case is of 
>> long period, then probably some level outburst is expected to happen. 
>> Then the timing also should be quite good, to about (almost) the 
>> accuracy of the observations of this in 1930, (well) better than an 
>> hour is expected now.
>>
>> If it is not of a long period, then probabaly nothing is observed, at 
>> least based on this predition. There is of course the possibility of 
>> some other type shower and some meteors of this might bee seen. Then 
>> also not much of the timing of these can be said from this, except 
>> probably around the same solar longitude.
>>
>> As it appears from this, also negative observations are valuable. And 
>> if an outburst is observed, then hopefully a more reliable radiant 
>> can be derived from video and/or photographs of these.
>>
>> Table 3. in the Jenniskens book  “Meteor Showers & Their Parent 
>> Comets” (Cambridge University Press, 200
>> 6), "
>> has the table data of that paper.
>> And I see that the "2013 Meteor Shower Calendar of the IMO" mentioned 
>> (with link) by Karl, seems to contain the description of the 1930 
>> observations.
>>
>> Karl also asked:
>>
>> "Or is it just that we will be, in 2013, in a planetary configuration 
>> exactly similar to this of 1930? In that case, which planetary 
>> influences seems to be of importance?
>> "
>> With an about similar planetary configuration to some previous, the 
>> trail passes (near the node in question) at about the same distance 
>> from the Sun. So, for example the mentioned prediaction of 1995 AMO's 
>> was 60 years from the observed 1935 outburst, and in 60 years Jupiter 
>> makes about 5 revolutions and Saturn about 2, resulting an about 
>> similar configuration. But the trail encounters can also happen in 
>> quite different planetary situations. The distance of the trail from 
>> the Sun (near the node in question) varies typically by a few 
>> hundredths of au. And if the encounter is not near one extreme of 
>> these variation (as it is with the Lyrids, might say unfortunately 
>> because some of the "waves" are too small to reach enough), then an 
>> encouner can happen at two different "phases" of these variations 
>> caused primarily by Jupiter and secondly Saturn etc.
>> If I recall this correctly, the 2007 Aurigids outburst could not be 
>> actually predicted by means of similar planetary configuration, 
>> although Jupiter was not so far from the 1994 situation.
>>
>>
>> Esko
>
> I agree with Esko, one or two years ago I wrote in this list for a 
> possible out-burst of Gamma Delphinids utilizing the work of Jenniskens
> by means of a more approximate treatment by means of the Solar system 
> barycentre (http://adsabs.harvard.edu/abs/2003Icar..162..443L)
> but as I remember nobody saw this meteors. The best it's observe too 
> this year, in negative case we can only waste time but if we not 
> observe and the shower occur .....
> Best greetings.
> Roberto Gorelli
>