[meteorite-list] Very Bright Fireball Over Europe on Halloween Night

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu, 5 Nov 2015 07:01:01 +0000 (UTC)
Message-ID: <50445322.139222.1446706861898.JavaMail.yahoo_at_mail.yahoo.com>

Yes Doug,
I agree with you.
In fact, I witnessed the very scenario you described.

It was a long duration (earth-grazing) fireball that I was lucky enough to catch early-on in its flight.
While it was at high elevation the fireball was a bright-blue ball with a greenish coma.
As it streaked down to the horizon, it changed to a greenish-yellow flame, and as it approached
the horizon it became a much dimmer, reddish sparkler.
The flight-path gave me the distinct impression that the fireball was travelling away from me,
much more than it was travelling downward.
This helped me rationalize that the fireball hadn't really "dimmed" in brightness at the horizon.
I was sure that it was just as bright and bluish-green for any lucky observers down-range and
who were directly beneath the fireball, at the same point in its flight-path where I perceived it
as being "reddish".
Just as you worded it, Doug, the color changed "the same way that the sun can appear
red at sunset, viewed at a low angle through more atmosphere."

So, were in agreement then, that
color AND magnitude are in the eye [and view angle] of the beholder.
Bob V.
--------------------------------------------
On Wed, 11/4/15, Doug Ross via Meteorite-list <meteorite-list at meteoritecentral.com>
 To: "Meteorite List" <meteorite-list at meteoritecentral.com>
 Cc: "Matson, Rob D." <ROBERT.D.MATSON at leidos.com>
 Date: Wednesday, November 4, 2015, 7:25 PM
 
 Thanks for the very informative and interesting discussion.
 Could the altitude, angle and distance from which a meteor is viewed
 also affect perceived color?
 Seems to me that the air between the fireball and the witness might
 significantly filter the colors, in the same way that the sun can appear
 red at sunset, viewed at a low angle through more atmosphere.
 
 Doug Ross
 
 
> HI All,
>
> Marco took the words out of my mouth. Getting tired of hearing that a green
> meteor tells you anything about its composition. I know that it's natural
> for people to think the most important thing they can report about a meteor
> is its color, but I wish various broadcast media would do the public a
> service and disabuse them of this notion. It would be far better if witnesses
> could be trained to get in the habit of counting the duration accurately,
> and noting the exact time of the meteor to the nearest minute. Seeing as
> how almost everyone has a cell phone these days, and all cell phones have
> accurate clocks, there really is no excuse to get the time wrong. Yet even
> a casual browse of the AMS fireball site reveals that people clearly don't
> think getting the time right is important. And even more obvious is that
> most people have no business reporting anything about fireball starting
> and ending bearings and elevation angles.? --Rob
>
> -----Original Message-----
> From: Meteorite-list [mailto:meteorite-list-bounces at meteoritecentral.com]
> On Behalf Of Marco Langbroek via Meteorite-list
> Sent: Wednesday, November 04, 2015 12:06 AM
> To: meteorite-list at meteoritecentral.com; baalke at zagami.jpl.nasa.gov
> Subject: Re: [meteorite-list] Very Bright Fireball Over Europe on Halloween Night
>
>> A lot of folks say it looked green to them, which means it may have been
>> metallic;
>
>
> It is a perpetuated misunderstanding that meteor colours are primarily due to
> their composition. It's a science myth inspired by High School Bunsen burner
> experiments that appears hard to kill.
>
> While composition in some cases does have some influence on the colour, it is
> actually the composition of the atmosphere that is usually dominant for our
> perception of meteor colours.
>
> That certainly is true for green colours. Meteor spectra show that meteors
> usually are very strong at the "forbidden" Oxygen line at 5577 Angstrom (557.7 nm).
> This line is due to atmospheric Oxygen, the same atmospheric Oxygen
> exitation line also responsible for the green colours of Aurora.
>
> So green meteor colours are likely atmospheric in origin and say little
> about the meteoroids' composition.
>
> - Marco
>
> -----
> Dr Marco (asteroid 183294) Langbroek
> Dutch Meteor Society (DMS)
>
> e-mail: dms at marcolangbroek.nl
> http://www.marcolangbroek.nl
 ______________________________________________
Received on Thu 05 Nov 2015 02:01:01 AM PST