(meteorobs) Terrific night of Geminids in central Alberta

[Bruce McCurdy]

Finally got around to transcribing my results from my observing session on
the Geminids pre-peak night, 2012 Dec 12-13. I got 3.00 hours Teff between
08:52 and 11:59 UT (about two to five o’clock local time = MST). It probably
took me longer in real time to transcribe my audio tape, tote up the
results, and submit my report to IMO than I actually spent under the stars! 

 

That’s a price I’m prepared to pay for a night that includes a couple
hundred meteors, as Thursday morning did. Turns out I pretty much nailed it
right after I got home when I gave this preliminary report to the MeteorObs
list:

 

“I got just over 100 recordings and I’d be surprised if my average was much
less than two meteors per recording. In fact, I’ll take the “over”. They
were happening in bunches all night, with some interesting cases of
simultaneous meteors or nearly so (where the second one started before the
first was done). A few fireballs in the mix.”

 

So I had to laugh when my 102 recordings turned out to contain 205 meteors,
for an average of 2.01 meteors per recording. I’ll take the “over”, indeed! 

 

169 of those were Geminids, of an average magnitude of +1.9 with hourly
counts of 57, 61 and 51. I also saw members of five other showers, including
a couple of very late (suspected) North Taurids. I know their season is
deemed to end around Dec 10, and if that’s an absolute date I guess I saw a
couple of sporadics masquerading as North Taurids. But my best guess is that
I happened to catch a couple of outliers. 

 

The clumping was apparent from my first entry (literally, three meteors
within ten seconds of my turning on the voice recorder to start my session)
to the last (four within 20 seconds). Such is  standard fare on meteor-rich
nights and is surely random distribution for the most part, although there
were a couple of cases of meteors that appeared to be related. On this night
of plentiful meteors I had four cases where two meteors were visible at
once, including two instances that were exactly simultaneous at both
beginning and end points. 

 

One of these events was a pair of Gems of mags +3 and +4 that straddled
Orion, plummeting to either side of the Hunter. The other was especially
interesting, a closely matched pair of short meteors very near the sigma
Hydrid radiant, from which they were heading to crudely nine and ten o’clock
position angles. They appeared exactly at the same moment, one (just) above
the other, and diverged slightly as they headed east and away from the
radiant, which was exceedingly well-defined at that moment! By the end of
their path they were still within 1° of each other. They were pretty much
identical twins, both judged at mag 3, as close to equals as cat’s eye
double stars like Porrima or Mesarthim appear in a telescope. But with the
added element of duration; the simultaneity was essentially perfect. I have
never quite seen the like.  Is there such a thing as a split meteoroid? 

 

Another interesting duo was mismatched, a zeroeth magnitude Geminid and a
second mag December Leo Minorid at roughly 90° angles to each other nearly
crossing swords down below both radiants (and between the two in RA). The
DLM was a split second “late” for its appointment or that would have
happened. 

 

In all I had 31 negative magnitude meteors, 29 of these Geminids. Of the six
that were mag -3 or brighter -- Jupiter was a very handy comparison star on
this night! -- four occurred in the last half hour. Brightest of all was
adjudged to be -6, with a deep, almost burnt orange hue and a brilliant
flashpoint. The -5 I saw was also in the red part of the spectrum, but
otherwise the predominant colour was green to blue-green, with about six
examples. Mostly they were white or nearly so, with few persistent trains as
is normal for the Gems. 

 

I faced south throughout, even as the Geminid radiant crested fairly early
in my session and thereafter the bright stars of the Winter Hexagon began to
dip towards the sky glow of the city in the west. I opted not to do any sort
of FM radio monitoring, but instead enjoyed the profound silence of the
December overnight. In the middle hour there were very few vehicles on the
main highway 4 km to the north, so even the low end hum was all but gone.
The coyotes were around but never kicked it into gear, and I never heard a
bird at any time, not even an owl. The only startling noise: a couple of
loudish staccato notes that reminded me of the crack of a baseball bat, but
which surely were the cracking of ice! It was a cold enough night with the
temperature ranging from -17 to -20 C, and ice fog that reflected the snow
and whitened the horizons in all directions even as I never saw a wisp of
cloud all night. Despite it being New Moon my limiting magnitude was only
5.9, but what a treat that was after having been confined to the city.

 

Indeed this was my first meteor session since the (also-good) Perseids,
after being skunked for all of the Orionids, Taurids, and Leonids this fall.
But as of now I no longer feel even slightly unlucky, as one is fortunate to
have one night such as this in a year. 

 

Bruce

*****

PS: IMO observing summary here:
http://vmo.imo.net/imozhr/obsview/view.php?id=11605 

 

 

 

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