(meteorobs) re Wonderful turquoise fireball ! - New Mexico

metpaper at Safe-mail.net metpaper at Safe-mail.net
Mon Jan 2 10:08:33 EST 2012


Nice!

Aphelion near Jupiter always brings Jupiter Family Comets to mind (present and past and to be), but couldn't find a comet match.  Given the inclination comet seemed more appropriate than near Earth asteroid, though at 33 degrees inclination probably not totally impossible, the latter.

Anyway, I then dropped it through all the available meteoroid orbits I'm aware of that are readily accessible and found eight recent matches (past few years).

Doesn't necessarily mean it'd be a "new"ly formed shower, recent surveys are all time, all sky, whereas past ones used to be occasional and targetted around major showers both temporally and spatially.  The all time and all sky ones are increasingly finding showers that are occuring at times of year such that there radiants are only just above the horizon that time of year and either spatially, temporally or both away from higher altitude or more traditional showers (eg the current quadrantids).

Anyway, they spread out from about 29th Dec to 6th Jan, bottom right corner of CMa and top left corner of Col part of the sky, mostly fairly widely spread (though most are caught by Northern surveys at very low altitude so may well affect accuracy of radiant solutions???).  No fireballs, but around 0 to 2nd mag on the whole, one near mag -2.  Geocentric velocities in the high twenties of km/s.

Doesn't seem to be a working list candidate that matches at this Solar Longitude, the epsilon Columbids are some way off yet and about ten km/s out.

On the other hand, the matches aren't the best.  I use Jopek's variant of Southworth & Hawkins, the latter canonically has an upper threshold of 0.15 on it's d' selection criterion.  The found matches were in the range 0.09 to 0.15, and ideally you want as small a value as possible for the greater certainty, so usually something below .1 is preferred, but not essential, indeed sometimes objects over 0.15 can still be associated.  Trouble also is that with the Jupiter Family Comets of present and past populating this part of space the assumption of a truly random distribution with aphelia near Jupiter doesn't quite apply, they seed certain parts of the sky with meteors at certain times of the year.  Then again, again, those sorts of comets and meteors usually lie within six degrees or so inclination of the ecliptic plane, whereas these mentioned here are up in the thirty degree plus inclination range.

Below is a link to their orbit plot, the 'turquoise' fireball orbit is included and is amongst the ones with the aphelia just inside the Jovian Orbit.

http://oi40.tinypic.com/95u74g.jpg

There being nothing in older datasets is more likely to be an absence of evidence than an evidence of absence case, and the circumstances of any shower are not going to be good (in the North rising early hours of the morning and the Moon's going to be fairly closeby some years) for having been particularly noted before.  One or two other candidates could be a coincidence, eight a bit beyond that, however spread out a bit in time and space, yet quite a few showers are like that, often more so.  Inclination of orbits suggests not just coincidental ecliptic plane JFC stuff.

Or in summary, Nice!

Still a coupla nights left for any potential other meteors from this putative radiant to be seen...  No idea if Southern Hemisphere observers would find things a lot easier with such a potential shower.

Cheers

John

John Greaves

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Original message :-

Have a decent solution on this event:

Start point: 107.52 W, 33.10 N at an altitude of 97.6 km
End point: 108.21 W, 33.77 N at an altitude of 82.4 km
Speed: 26.1 km/s
Radiant coordinates:  RA 91.392 +/-  0.07 deg, Dec -32.753 +/-  0.04 deg 

Note: end point is where the meteor exited Mayhill camera FoV - not actual ablation height of the meteor.

Mass (lower bound): 200.0 grams
Diameter (assuming density of 2.5 g per cc): 5.3 cm

Orbital parameters:

a - 2.851 +/-  0.2 AU  
e - 0.693 +/-  0.02     
incl - 33.4 +/-  0.4 deg 
omega - 43.2 +/-  0.4 deg 
asc_node  99.9 +/-  0.0 deg 

Orbit plot - this meteor is the one in orange, with an aphelion near the orbit of Jupiter.

http://www.billcooke.org/events/NM_20120101/orbits_20120101.jpg

A very nice event, Thomas!

Sent from my iPad
Bill

On Dec 31, 2011, at 10:25 PM, Thomas Ashcraft <ashcraft at heliotown.com> wrote:

> Dec 31, 2011 - 8:15 pm   ( Jan 01, 2012  0315 UT)
> 
> Wow.  There was a beautiful turquoise large magnitude fireball  ( maybe 
> -11 or so -  hard to say since I saw it through a window )  that just 
> occurred heading from southeast to northwest over north central New Mexico.
> 
> What a blessing to see it live and I also caught it on camera.  There 
> should be many reports on this fireball since it is New Years Eve and 
> people are out and about.
> 
> Movie will be posted soon.
> 
> Happy New Year.
> 
> Thomas Ashcraft near Lamy, New Mexico


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