Marco, Rob... this discussion is timely. what you've noted is exactly my understanding. just yesterday I came across a high-profile blog about these fireballs, and the writer stated that most of the light comes from the superheated vaporized particle as it ablates. suspecting this was wrong, I looked in several places for the correct information -- IMO, AMS, RASC Handbook, etc -- and yet I didn't really find the physics spelled out explicitly. (maybe I was looking in the wrong places?) the closest I came was this post by Peter Jenniskens (http://leonid.arc.nasa.gov/meteor.html), which was equivocal.
clear skies, Kelly ******************************* J. Kelly Beatty Senior Editor, Sky & Telescope SkyandTelescope.com (a division of F+W, a Content + eCommerce Company) 617-864-7360 x22168 @NightSkyGuy -----Original Message----- From: Meteorite-list [mailto:[email protected]] On Behalf Of Rob Matson via Meteorite-list Sent: Wednesday, November 04, 2015 3:54 AM To: 'meteorite-list' Subject: Re: [meteorite-list] Very Bright Fireball Over Europe on Halloween Night 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:[email protected]] On Behalf Of Marco Langbroek via Meteorite-list Sent: Wednesday, November 04, 2015 12:06 AM To: [email protected]; [email protected] 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: [email protected] http://www.marcolangbroek.nl ______________________________________________ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list [email protected] https://pairlist3.pair.net/mailman/listinfo/meteorite-list ______________________________________________ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list [email protected] https://pairlist3.pair.net/mailman/listinfo/meteorite-list
