Green meteor/fireball sighting?

Originally posted by zorgon

Don't recall mentioning the oxygen in THIS thread but that is true... However the composition does play a role.

Yes, it does play a role, that's why I said "the color is mainly due to gases".

Originally posted by zorgon

Vivid colors are more often reported by fireball observers because the brightness is great enough to fall well within the range of human color vision. These must be treated with some caution, however, because of well-known effects associated with the persistence of vision. Reported colors range across the spectrum, from red to bright blue, and (rarely) violet. The dominant composition of a meteoroid can play an important part in the observed colors of a fireball, with certain elements displaying signature colors when vaporized. For example, sodium produces a bright yellow color, nickel shows as green, and magnesium as blue-white. The velocity of the meteor also plays an important role, since a higher level of kinetic energy will intensify certain colors compared to others. Among fainter objects, it seems to be reported that slow meteors are red or orange, while fast meteors frequently have a blue color, but for fireballs the situation seems more complex than that, but perhaps only because of the curiousities of color vision as mentioned above.

www.amsmeteors.org...

Notice what I have highlighted above. The key word here is 'can'. In the case of green meteors, it's the Oxygen glowing green. The composition has little or no visible effect. When a meteor is bright, the composition seems to play a larger role, but the color displayed is usually something other than green.

As for meteors being a conspiracy, that makes about as much sense as saying the sky being blue is a conspiracy. Get a grip and stop spouting BS about things you know little or nothing about

[edit on 12-12-2008 by C.H.U.D.]

reply to post by zorgon


If they stop "glowing" that high up then what kind of optical illusion would cause me to perceive the object still lit up at the height of tall pine tree tops.

This really bugs me as it really did appear to at tree top level and it appeared to have disappeared vertically behind trees and houses as if it was going to impact.

I really need to find someone else from the area who observed it. It would help answer if somehow it was an optical illusion that affected my observation.

Bear in mind that I was in the Army seven years (and work for the Air Force now) and have observed numerous star clusters, flares, illuminated rounds, and tracers. This object was traveling very fast and appeared to be at a very low altitude.

Originally posted by MikeboydUS
If they stop "glowing" that high up then what kind of optical illusion would cause me to perceive the object still lit up at the height of tall pine tree tops.

This really bugs me as it really did appear to at tree top level and it appeared to have disappeared vertically behind trees and houses as if it was going to impact.

Mike - it's a combination of things:

Firstly, our eyes and brain find it very hard to judge the distance of lights at in the sky at night. With very few visual clues, our brains make assumptions to fill in the gaps.

See this page which deals with meteors specifically: www.meteorobs.org...

Secondly, we live on the surface of a sphere - seeing a meteor only just above the horizon means that it's further away, not lower in altitude. Most meteors burn up/stop glowing between 100 and 70 km altitude, unless they are extremely large, and those are extremely rare.

This diagram illustrates the principal:



Does that answer your question?

[edit on 12-12-2008 by C.H.U.D.]

reply to post by C.H.U.D.


It makes sense.

I wish I could still find someone else who was a witness though. That was the original point of the thread and would really help clarify what I saw.

I'm guessing space junk and debris "goes black" at the same altitudes the meteors do?

reply to post by MikeboydUS


It depends on the junk, but for small objects, for all intents and purposes they enter the 'dark flight' phase at more or less the same height as natural meteors.

Satellites and orbiting junk travel no faster than the slowest meteors (about 10km/s) , so you can rule out junk if it was relatively fast. No doubt you've seen some satellites in your time, so you should be able to rule them out yourself if that is the case.

If it was slow and quite long lasting it could well have been junk. Meteors are usually gone in under a second or two. It may be impossible to tell for sure. If you really want to know, the best way IMO is to familiarize yourself with meteors (and possibly junk at the same time if you are lucky).

What better opportunity to start than the Geminids, which is peaking over the next 24-36 hours!

It may also have been a Geminid you saw, so try and catch a few over the next couple of nights to try to rule them out at least IMHO.

Incidentally, the Geminids enter the atmosphere at about 35km/s, which is considered to be medium speed for a meteor. Note that how fast a meteor appears to travel is heavily dependent on perspective - a meteor traveling directly towards you will not appear to move at all! The true speed of a meteor can only be gaged when you know roughly where the radiant is/what shower it belongs to - only meteors seen high in the sky and away from their radiant appear to travel at their 'true velocity'.

If you're not sure what the radiant is, I've explained it here.

On Dec. 29, 2008 in Avon, Connecticut, I was looking due east when at 9:29pm est. I observed a very bright blue-green ball of light traveling from the NNW to SSE at about a 45 degree angle to the horizon It lasted only about 4 seconds and then was gone. I called the local police to see if anyone else had witnessed this and called it in but they hadn't gotten any calls. In relation to a star in the sky this was like a basketball relative to a golf ball or smaller.