Green Meteor?
October 5, 2010 10:00 PM   Subscribe

Astronomy Filter. I have a friend who has seen (what I think to be) several meteors this year. Trouble is, they were green. Also, they weren't the usual streak across the sky, more like a Roman Candle, with no tail. What are they?

Details: Beaver Dam Wisconsin (South Central part of the state). Four separate incidents, months apart. All in 2010. Time is about 11:00 pm -- which can mean hours after sundown (depending on the season), or only an hour after sundown. Trajectory appears to him as horizontally across the sky, rather than sky to Earth (as I have seen them). Brightness is firework quality (he and I have only seen much fainter traces); meaning also probably not a reflection of a satellite. Direction: East to West generally. One newspaper link: Portage County Daily Register. Although reported as "probably" a meteor, no physical evidence was found. Since these sightings happened several apart, he wonders, Is this possibly a man-made phenomena? Or can it be entirely natural? And the $64.00 question, did anyone else see these (or is there some kind of database to check for sigthings)
posted by IvanKalinin to Science & Nature (8 answers total) 1 user marked this as a favorite
Fireball Monitoring Program allows for self reports. A few years ago I saw one in Rhode Island and noticed someone had seen the same one I had reported.

Are all the meteors you friend has seen green? Have they seen normal colored ones also?
posted by bottlebrushtree at 10:13 PM on October 5, 2010

Sounds like you are talking about Earthgrazers. The most famous probably being the Great Daylight Fireball of 1972. I am almost 100 percent certain this is what you have seen. Incidentally, in April 2010 there was a bright green fireball seen over several Midwestern states, including Wisconsin. It's unsurprising that there have been no physical traces of these fireballs as they tend to kind of skip off the atmosphere (and most of these things that do enter the atmosphere are destroyed upon entry into the atmosphere).

As for the green color I remember reading that the predominant color of meteors had to do with trace elements within the object itself, burning up on entry into Earth's atmosphere but am unable to find a link to corroborate this.
posted by IvoShandor at 1:21 AM on October 6, 2010

Actually, IvoShandor, the color would be based on non-trace elements. That is, the color is dominated by the principal ingredients in the asteroid that becomes the meteor(ite).

The color is based on oxidation (burning). We're used to quasi-blackbody radiation - that is, as materials get hot, they turn red, then yellow, then white. But some pure materials are noted for their distinct spectral outputs during oxidation: strontium glows a unique color of red, sodium bright yellow, and copper green.

The lack of a tail indicates that there simply wasn't a lot of debris being stripped off of the meteor as it burned. Imagine the difference between running with a sparkler, and running with a flare. The flare will trail smoke (invisible at a distance), but most of the burning material occurs in the runner's hand. The sparkler sheds burning material which would trail behind, forming a sort of tail.

Thus, a tailless meteor is more "solid" (less prone to shedding sizable, visible burning chunks of itself) than a meteor with a tail.
posted by IAmBroom at 5:28 AM on October 6, 2010 [2 favorites]

The fact that there is no trail, and they were seen around 1 hour after sunset (or a little before dawn works as well) suggests that they could be Iridium Flares. I've observed some of these to appear greenish and they're sometimes very bright. Fortunately this is a very easy question to answer, because its possible to exactly predict (For Beaver Dam, WI) when they will occur so your friend can go look at one and see if they match with what he has seen previously.
posted by Long Way To Go at 8:27 AM on October 6, 2010 [2 favorites]

Iridium flares?
posted by psylosyren at 8:37 AM on October 6, 2010 [1 favorite]

Ooop. Refresh fail.
posted by psylosyren at 8:38 AM on October 6, 2010

Sorry, I got the latitude/longitude wrong for Beaver Dam in the link above. It should be Beaver Dam, WI.
posted by Long Way To Go at 9:28 AM on October 6, 2010

Thanks for clearing up my misunderstanding on that IAmBroom.
posted by IvoShandor at 11:09 PM on October 6, 2010

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