(meteorobs) Green Fireballs

[Norman W McLeod III]

I have been through the busy first peak of tax season during the last 
two weeks, with longer office hours combined with a mild cold that keep 
me sleeping extra hours.  So a reply about green fireballs had to wait.  
This topic has come up several times before, sometimes started by 
someone who lucks into seeing two green fireballs within a short time.

Most sporadic fireballs I have seen brighter than -5m are a rich emerald 
green color.  But shower fireballs are rarely the same, more like 
blue-green or some other color.  The only shower with several green 
meteors in one night regularly is the Geminids.  No other shower has 
ever produced noticeable extra green meteors for an isolated night.  
Neither the 1980 nor the 1981 Perseids were unusual in that regard.

For colors in general, I tallied up colors on everything from 1971 to 
1981 some time ago.  There had been notions of blue Quadrantids, orange 
Taurids, and other yellow showers.  But my results showed no variation 
among the showers.  My dominant color is yellow for about 60% of all my 
meteors, with about 20% each for blue and orange.  Then a handful are 
other colors.  The most common binary color is blue-green.  In my 
earlier years I saw some blue-pink Perseids, but they changed to 
blue-purple as I got older.

One color I never see is pure red.  The best I can do is red-orange in a 
ratio of two to one.  More commonly it is orange-red in the same ratio.  
But twice I saw a meteor release a shower of orange sparks in its wake, 
with a single red spark.

A color-intensity scheme I developed is as follows : 1-subtle (most star 
colors), 2-moderate (the strongest star colors), and 3-intense (like 
airplane lights).  My general color intensity perception is about 20% 
subtle, 40% moderate, and 40% intense.  Evidently my color perception is 
very good, as opposed to general meteor rates where I am just average.  
No matter how poorly I see a meteor, I still get its color.  That 
includes the ground lighting up from a fireball that I miss, or a light 
dome from a fireball low in the sky with my view of the object blocked.  
The most memorable example of the latter came in 1974 July: a bright 
green dome appeared in my south, coming on gradually for a second, 
staying steady for two seconds, then fading out for the final second.  
Obstructions kept me from seeing the meteor, a big disappointment.

A pure white meteor is very rare for me.  Many people describe meteors 
as white, even very bright ones.  I have the impression that about half 
the population perceives no color at all in either meteors or stars, or, 
at best, just an occasional subtle color.

Another breakdown is color versus magnitude.  Obviously, a meteor needs 
to be bright enough for the eye to get a color.  My color perception by 
magnitude: all meteors +1m and brighter, about half at +2m, about a 
tenth at +3m, a handful at +4m and always deep orange, then rarely an 
orange +5m.

The subject of color has always interested me because I see it so well.  
I have wanted to see some similar detailed workups for other observers 
but all these years no one has gotten around to doing it.  Probably no 
two observers will be the same.  Two co-observers from the past, Felix 
Martinez and Lew Gramer (the holy GRALE), I am aware have green as one 
of their dominant colors.

Norman