(meteorobs) Potential gamma-Delphinids return, June 2013

Skywayinc at aol.com Skywayinc at aol.com
Sun May 5 23:34:37 EDT 2013


 
Continuing along the lines of this discussion, has  Jeremie Vaubaillion 
come up with one of his computer simulations showing the  Earth's 
interaction 
with this particular meteor stream (similar in many  respects 
to the 2007 Aurigid shower)?
 
-- joe rao
 
 
 
 
In a message dated 4/28/2013 2:34:41 P.M. Eastern Daylight Time,  
karl.antier at laposte.net writes:
 
Dear Esko, Roberto and all,

Thanks a lot for those detailed  answers and the time spent to write them!

> 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.

For those  interested, I just found this link with the  article:
http://dmsweb.home.xs4all.nl/publications/icaruslp-final.pdf

Clear  skies!
Karl








In a message dated 4/28/2013 10:43:09 A.M. Eastern Daylight Time,  esko.
lyytinen at jippii.fi writes:


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
>

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