[Prev][Next][Index][Thread]
Re: (meteorobs) meteor colors
In a message dated 96-10-05 14:40:23 EDT, you write:
<< Thank you for your replies to my enqiry about meteor (perceived) colors,
all
very interesting.
I did see another explanation on a local TV news broadcast last night when
they interviewed Ed Krupp, who is the Director of the Griffith Observatory,
here in Los Angeles. He speculated that the color seen is a result of the
height of the meteor above the ground. He said that as it enters the upper
atmosphere it glows green then turns yellow as it gets lower. He didn't
mention red or orange.
This may tie in with Bob's Northern Lights analogy, except for one thing.
Bob also mentions green being caused by the excitation of the oxygen
molecules in the atmosphere. The problem is that oxygen is rareified in the
upper atmosphere, so I would expect it to glow green in the lower
atmosphere, if that were the case.
Does anybody else have an opinion on that?
Ron.
>>
-----------
I would like to add to what I said earlier about some meteor colors may be
due to entry angles, radiant locations etc. I recall the Alpha Auriga
Outburst that Lunsford and I witnessed in 1994 (WGN Dec 1994). The radiant
was very low on the horizon, but nearly every meteor from that radiant was
green for me and blue for Robert. Outside of that 1 hour peak period they
were white.
As to a fireball changing colors as it passes thru various atmospheric layers
or densities...seems reasonable to me. I've seen them change thru all sorts
of colors as it made it's way down...The -15 fireball that Bob and I
witnessed in Dec of 1993 did just that...in the end it was a deep red for a
few degrees before extinguishing...a few minutes later the sonic boom
followed. As for a fireball being green deep in the atmosphere as well as
the rarefied upper layers... it's hard to tell since I don't know how high up
the event is occurring...unless a sonic boom is given off, then I am given a
clue that it's at least reached about 30 miles above the surface. I've only
heard one meteor caused sonic boom out of about 250...So, I can't really say
from experience that fireballs do or don't give off a green color deep in the
atmosphere. By then the meteor is slowing down though. If they don't exhibit
a greenish color then, maybe the energy is insufficient at the end to excite
a significant amount of oxygen atoms to make green that obvious? Maybe the
concentration of Nitrogen has something to do with colors at the lower
levels? I don't know if the percent of Nitrogen to oxygen is the same at
higher levels. But with dissipating energy and changing atmospheric
densities and perhaps different elements in the air, all kinds of variable
factors arise that may change a meteors color as it travels closer to the
earth. Then there are fireballs that I've seen that shows no color at
all...but the most predominant color that I do see for fireballs is green.
On occasions I see some blues as well. But the blues and green colors I see,
usually looks sort of like a halo around a glowing reddish or orange white
interior.
Personally, when it comes trying to interpret meteor colors, I relate it more
to a dog chasing it's own tail...you are never really going to get anywhere.
George Z.
Follow-Ups: