by Ann » Thu Dec 28, 2023 6:39 am
shaileshs wrote: ↑Thu Dec 28, 2023 5:20 am
Hmmm,,, quick questions -
1) Brightest portion in the middle.. is that where the friction with Earth's atmosphere is the strongest (e.g. left origin up above atmosphere, so not that bright, right ending portion after the max burn falling down from sky) ? Or some other reason ?
2) Why blue-green light (i'd imagine it's based on composition/material of asteroid and if so, what's it made up of) ?
Thanks in advance to all answers/thoughts. I appreciate Ann and ChrisP, they respond most times to most people to most queries.
I wish I knew, but meteors are not my forte at all. Chris should be able to provide you with good answers.
Nevertheless, I can say a few things. Take a look at this composite picture of Geminid meteors:
Note that the brightest meteor, at left, is clearly blue-green in color. But the fainter meteors are not green at all, certainly not blue-green. The fact that only the brighter meteors are blue-green certainly suggests to me that the size and mass of the meteor contributes to the green color, i.e., it takes a "powerful impact" between the meteor body and the Earth's atmosphere to create the green color. I think it has to do with the amount of energy created by meteor.
You can see the blue-green color of a bright meteor over Colorado:
Click to play embedded YouTube video.
However, not all bright meteors are green, although I do believe that many are. But the brightest meteor in recent years, the bolide over Chelyabinsk in Russia in 2013, does not appear to have been green at all. But if you watch the video below, you can hear loud "booms" as the meteor exploded.
Click to play embedded YouTube video.
I think that smaller meteors also "explode", at least sometimes. If you look at the first picture I posted, you can see two little brightenings in the trail of the brightest meteor. I would guess that those are little explosions as the pebble from space burnt up in the Earth's atmosphere.
It seems reasonable to me that the green color of many bright meteors might just possibly be related to the green color of comet comas:
The cause of the green color of comet heads appears to be dicarbon, or C
2.
https://newsroom.unsw.edu.au wrote:
The key player at the centre of the mystery, dicarbon, is both highly reactive and responsible for giving many comets their green colour. It’s made up of two carbon atoms stuck together and can only be found in extremely energetic or low oxygen environments like stars, comets and the interstellar medium.
Dicarbon doesn’t exist on comets until they get close to the Sun. As the Sun starts to warm the comet up, the organic matter living on the icy nucleus evaporates and moves to the coma. Sunlight then breaks up these larger organic molecules, creating dicarbon.
The UNSW-led team have now shown that as the comet gets even closer to the Sun, the extreme UV radiation breaks apart the dicarbon molecules it recently created in a process called ‘photodissociation’. This process destroys the dicarbon before it can move far from the nucleus, causing the green coma to get brighter and shrink – and making sure the green tinge never makes it into the tail.
Well, the process creating the green heads of comets doesn't seem to be the same as the process creating blue-green color in bright meteors. But the colors are similar. In any case, the color is caused by the matter and chemicals of the "meteor body" reacting to the rapidly increasing heat and pressure as it falls through the Earth's atmosphere. But you knew that already.
As for why the meteor is brightest in the middle, well, consider the Chelyabinsk meteor: First it was faint, then it got bright, then it got faint again. And actually, I think we can see signs of little explosions in the middle of the trail of the bright meteor of the APOD.
That is the best answer I can give you!
Ann
[quote=shaileshs post_id=335931 time=1703740840 user_id=143908]
Hmmm,,, quick questions -
1) Brightest portion in the middle.. is that where the friction with Earth's atmosphere is the strongest (e.g. left origin up above atmosphere, so not that bright, right ending portion after the max burn falling down from sky) ? Or some other reason ?
2) Why blue-green light (i'd imagine it's based on composition/material of asteroid and if so, what's it made up of) ?
Thanks in advance to all answers/thoughts. I appreciate Ann and ChrisP, they respond most times to most people to most queries.
[/quote]
I wish I knew, but meteors are not my forte at all. Chris should be able to provide you with good answers.
Nevertheless, I can say a few things. Take a look at this composite picture of Geminid meteors:
[img3="Geminid meteors. Credit: Sky & Telescope Associate Editor Sean Walker"]https://res.cloudinary.com/graham-media-group/image/upload/f_auto/q_auto/c_scale,w_900/v1/media/gmg/OVX4WSQSJZAU3OVLFPL3GZUABI.jpg?_a=AJFJtWIA[/img3]
Note that the brightest meteor, at left, is clearly blue-green in color. But the fainter meteors are not green at all, certainly not blue-green. The fact that only the brighter meteors are blue-green certainly suggests to me that the size and mass of the meteor contributes to the green color, i.e., it takes a "powerful impact" between the meteor body and the Earth's atmosphere to create the green color. I think it has to do with the amount of energy created by meteor.
You can see the blue-green color of a bright meteor over Colorado:
[youtube]https://www.youtube.com/watch?v=-7b6NLbx8lw[/youtube]
However, not all bright meteors are green, although I do believe that many are. But the brightest meteor in recent years, the bolide over Chelyabinsk in Russia in 2013, does not appear to have been green at all. But if you watch the video below, you can hear loud "booms" as the meteor exploded.
[youtube]https://www.youtube.com/watch?v=dpmXyJrs7iU[/youtube]
I think that smaller meteors also "explode", at least sometimes. If you look at the first picture I posted, you can see two little brightenings in the trail of the brightest meteor. I would guess that those are little explosions as the pebble from space burnt up in the Earth's atmosphere.
It seems reasonable to me that the green color of many bright meteors might just possibly be related to the green color of comet comas:
[img3="Man watching a comet with a blue-green head. Credit: Unsplash."]https://newsroom.unsw.edu.au/sites/default/files/styles/full_width__2x/public/thumbnails/image/man_sitting_on_hill_gazing_up_at_green-headed_comet_flying_in_night_sky_unsplash_hao_wen_3.jpg?itok=0_buTarP[/img3]
The cause of the green color of comet heads appears to be dicarbon, or C[sub][size=85]2[/size][/sub].
[quote][url=https://newsroom.unsw.edu.au/news/science-tech/comets-heads-can-be-green-never-their-tails-after-90-years-we-finally-know-why]https://newsroom.unsw.edu.au[/url] wrote:
The key player at the centre of the mystery, dicarbon, is both highly reactive and responsible for giving many comets their green colour. It’s made up of two carbon atoms stuck together and can only be found in extremely energetic or low oxygen environments like stars, comets and the interstellar medium.
Dicarbon doesn’t exist on comets until they get close to the Sun. As the Sun starts to warm the comet up, the organic matter living on the icy nucleus evaporates and moves to the coma. Sunlight then breaks up these larger organic molecules, creating dicarbon.
The UNSW-led team have now shown that as the comet gets even closer to the Sun, the extreme UV radiation breaks apart the dicarbon molecules it recently created in a process called ‘photodissociation’. This process destroys the dicarbon before it can move far from the nucleus, causing the green coma to get brighter and shrink – and making sure the green tinge never makes it into the tail.[/quote]
Well, the process creating the green heads of comets doesn't seem to be the same as the process creating blue-green color in bright meteors. But the colors are similar. In any case, the color is caused by the matter and chemicals of the "meteor body" reacting to the rapidly increasing heat and pressure as it falls through the Earth's atmosphere. But you knew that already.
As for why the meteor is brightest in the middle, well, consider the Chelyabinsk meteor: First it was faint, then it got bright, then it got faint again. And actually, I think we can see signs of little explosions in the middle of the trail of the bright meteor of the APOD.
That is the best answer I can give you!
Ann