(meteorobs) Leonids 2009 first peak

[Skywayinc at aol.com]

In a message dated 8/28/2009 6:42:28  A.M. Eastern Daylight Time, 
albireo3000 at yahoo.es writes:

I read at IMO  Calendar that the first Leonid peak is forecasted the 
17/11/2009 at 07:26  with THZ ~200. Do you have more information about 
it? I couldn´t find  anything  else.


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I  had E-mailed Jeremie Vaubaillion about this very subject this past  
Tuesday.

Much has been said about the impending "sub-storm" outburst  forecast for 
21h UT on Nov. 17, but Jeremie's diagram depicting that particular  shower 
also shows that Earth will be sweeping through the outer edge of another  
trail roughly between 6 and 10h UT.  Mikhail Maslov has identified this as  
material shed by 55P from the year 1567, which closely coincides with the  
Leonids "traditional" background activity and suggests a ZHR of 25-30.  I  wanted 
to know from Jeremie specifically what HIS model indicated for the 1567  
trial.

Now, let's backtrack for a moment to the 2009 Perseids . . . I had  noticed 
from Jeremie's diagram that we were going to pass through a very old  
debris trail (which he identified as dating back to AD 441!) at around 6h UT on  
August 13; I had previously alluded to it in two messages here on  
meteorobs.  

While I did not come right out and say that we might  see a significant 
outburst, those who were concentrating on the predicted  activity enhancement 
from the previous night (August 12) perhaps were taken by  surprise by the 
activity that occurred on August 13; the IMO now says that the  ZHR rose to 
>150 as a result of the interaction from that 441  trail!

See: http://www.imo.net/live/perseids2009/

Now . . . back  to Jeremie's Leonid diagram for 2009.  It appears at least 
to me, that  between roughly 08:45 and 10:15 UT on November 17, the activity 
intensity might  approach what was observed with the Aug. 13 Perseid 
enhancement.   

Another parallel could be made with the Leonids in 1999.  About 16  hours 
after a meteor storm was created by the 1899 and 1932 material, a smaller  
outburst was observed from material that was shed from 1866.  Once again,  the 
ZHR rose to >150.  I think this 1999 outburst parallels what might  be 
observed in 2009.  

You may compare Jeremie's depictions for  yourself:

2009 Leonids: http://tinyurl.com/kjpa7q
2009  Perseids:http://tinyurl.com/neachp 
1999 Leonids:  http://tinyurl.com/lcsw95

As for meteor brightness, based on the # of  revs for the trail (13), as 
well as ejection velocity of the particles coming  off the nucleus of 55P, my 
guess is that this upcoming 2009 display should fall  pretty much in between 
the relatively dim outbursts of 1969, 1999 and 2002 and  the brilliant 
outbursts of 1965 and 1998. I should point out that based on the  excellent 
Leonid paper he co-wrote with David Asher in the 1999 WGN, that Rob  McNaught 
pointed out that the relevant parameter is not so much the age of the  trail, 
but rather the parameter da0. The relationship between da0 and population  
index incorporates several factors, but to the first degree, the closer da0 
is  to 0.00 the brighter the meteors.  Unfortunately, I do not have a da0 
value  for the 1567 trail, but still . . . one would think that Earth will 
encounter at  least a few large particles. 

So perhaps North Americans . . .  particularly those living on US East 
Coast . . . will see, if for nothing else,  a "very entertaining" Leonid display 
this year.

-- joe rao