APOD: Milky Way and Exploding Meteor (2015 Aug 12)

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APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by APOD Robot » Wed Aug 12, 2015 4:06 am

Image Milky Way and Exploding Meteor

Explanation: Tonight the Perseid Meteor Shower reaches its maximum. Grains of icy rock will streak across the sky as they evaporate during entry into Earth's atmosphere. These grains were shed from Comet Swift-Tuttle. The Perseids result from the annual crossing of the Earth through Comet Swift-Tuttle's orbit, and are typically the most active meteor shower of the year. Although it is hard to predict the level of activity in any meteor shower, in a clear dark sky an observer might see a meteor a minute. This year's Perseids occur just before a new Moon and so the relatively dark sky should make even faint meteors visible. Meteor showers in general are best be seen from a relaxing position, away from lights. Featured here is a meteor caught exploding two weeks ago above Austria next to the central band of our Milky Way Galaxy.

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by alter-ego » Wed Aug 12, 2015 4:23 am

A pessimist is nothing more than an experienced optimist

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Chris Peterson » Wed Aug 12, 2015 5:04 am

To be clear, the only explosion here is the bright burst at the end of the meteor trail- the terminal explosion of the meteoroid. The expanding dust train is not an explosion, and is simply being dispersed by high altitude winds.
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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Ann » Wed Aug 12, 2015 5:05 am

Congratulations, André, this is a great Milky Way image and a great meteor explosion sequence! :D

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Joe Stieber » Wed Aug 12, 2015 5:06 am

If you're wondering about the identity of the background sky, here's a copy with some labels.

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by hoohaw » Wed Aug 12, 2015 9:03 am

Sure hope there was no damage to the Galaxy!

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Boomer12k » Wed Aug 12, 2015 12:54 pm

That is SO COOL....

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by BMAONE23 » Wed Aug 12, 2015 1:00 pm

hoohaw wrote:Sure hope there was no damage to the Galaxy!
Intergalactic war will not be averted if you don't hand over the galaxy...undamaged

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by biddie68 » Wed Aug 12, 2015 2:21 pm

Is it predicted that the Perseids will eventually all burn up? And, if so, in how many years?

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Chris Peterson » Wed Aug 12, 2015 2:56 pm

biddie68 wrote:Is it predicted that the Perseids will eventually all burn up? And, if so, in how many years?
All meteor showers are short lived in terms of geological time. They are caused by active comets which have Earth-crossing or near Earth-crossing orbits, and short periods (200 years or less). Such comets have a relatively short period of activity (typically a few thousand years before they stop outgassing), and these inner system orbits are not very stable, so they are likely to be shifted out of proximity with the Earth. Once a comet stops producing debris, what remains in orbit disperses over time.

It's difficult to predict the exact future of the Perseids. It's unlikely this shower will be around in a few thousand years. But it might last longer. The parent body is in a Jupiter resonant orbit which makes it more stable, and is very large, meaning it has a lot of material to outgas. Certainly, though, the shower won't persist longer than hundreds of thousands of years. (Almost none of the material burns up as meteors, because only a tiny fraction encounters the Earth. Most will end up decaying into the Sun.)
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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Ron-Astro Pharmacist » Wed Aug 12, 2015 3:55 pm

http://www.space.com/21195-56-000-mph-s ... video.html

I’ve wondered if there has ever been a report, or better yet video of a meteorite, of someone seeing a meteorite that was large enough and close enough to be seen all the way to the ground. It seems like with all of us on the Earth someone, somewhere would have seen one and reported it.

Also is a meteor’s speed due to the Earth’s orbital speed or the orbital speed of the comet’s matter (as say for the Perseids) or a combination of both?
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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Chris Peterson » Wed Aug 12, 2015 4:07 pm

Ron-Astro Pharmacist wrote:I’ve wondered if there has ever been a report, or better yet video of a meteorite, of someone seeing a meteorite that was large enough and close enough to be seen all the way to the ground. It seems like with all of us on the Earth someone, somewhere would have seen one and reported it.
Many meteorites have been observed to fall, and in some cases the preceding fireball was also observed. But the objects aren't large enough to see all the way. First there's the fireball, which is visible because of all the light it produces. Than any surviving fragments spend several minutes in dark flight. They are only a few centimeters across and are many kilometers away.
Also is a meteor’s speed due to the Earth’s orbital speed or the orbital speed of the comet’s matter (as say for the Perseids) or a combination of both?
Both.
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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Ron-Astro Pharmacist » Wed Aug 12, 2015 5:55 pm

Chris Peterson wrote:
Ron-Astro Pharmacist wrote:
Also is a meteor’s speed due to the Earth’s orbital speed or the orbital speed of the comet’s matter (as say for the Perseids) or a combination of both?
Both.
Thanks for both answers Chris. As fast as meteors seem to enter the atmosphere it’s hard to envision the interaction of the Earth’s orbit with the path of debris of the comet responsible for the Perseids that results in the speed of the meteors.
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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by ta152h0 » Wed Aug 12, 2015 6:43 pm

in Russia, couple February's ago ?
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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Chris Peterson » Wed Aug 12, 2015 9:52 pm

ta152h0 wrote:in Russia, couple February's ago ?
Nobody saw anything between the end of the ablation stage and ground impacts a few minutes later.
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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by saturno2 » Wed Aug 12, 2015 10:49 pm

Interesting image

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by alter-ego » Thu Aug 13, 2015 3:06 am

Chris Peterson wrote:To be clear, the only explosion here is the bright burst at the end of the meteor trail- the terminal explosion of the meteoroid. The expanding dust train is not an explosion, and is simply being dispersed by high altitude winds.
I agree that meteor terminated in an explosion. However, I am doubtful that the quite symmetric radial expansion is explained by winds. I believe they'd be more unidirectional, i.e. the cloud translates. I've seen glowing fireball residue disperse due to high altitude winds. Things moved and mixed, but didn't expand like a smoke ring.

I'm not saying the source of the debris ring is necessarily related to termination explosion per se, but it seems clear there's lateral momentum in the event. Could it be an illusion of dust continuing to move straight forward bringing out the vanishing point? Or maybe dust is responding to a pre-termination shock wave driving the dust outward?

Here's a Universe Today article of a similar exploding Perseid example in 2013.
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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by Chris Peterson » Thu Aug 13, 2015 6:17 am

alter-ego wrote:
Chris Peterson wrote:To be clear, the only explosion here is the bright burst at the end of the meteor trail- the terminal explosion of the meteoroid. The expanding dust train is not an explosion, and is simply being dispersed by high altitude winds.
I agree that meteor terminated in an explosion. However, I am doubtful that the quite symmetric radial expansion is explained by winds. I believe they'd be more unidirectional, i.e. the cloud translates. I've seen glowing fireball residue disperse due to high altitude winds. Things moved and mixed, but didn't expand like a smoke ring.
I think it's an illusion. These meteor dust trains typically extend through a significant depth of atmosphere- kilometers. The winds change significantly with height. This causes odd disruptions of the trail. Usually we see a lot of zigging and zagging. In this case, those zigs and zags happen to appear as a radial expansion. Unusual, but not that hard to understand. I think we'd see something quite different if the actual 3D structure were captured.

There's really no plausible physical mechanism to disperse a meteor train except the wind.
Chris

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Re: APOD: Milky Way and Exploding Meteor (2015 Aug 12)

Post by avdhoeven » Thu Aug 13, 2015 8:42 pm

To be honest I don't think it is an illusion, but we will never know for sure. It's clearly expanding in a straight line (I checked the images) at a regular interval. So that seems to be a constant motion that has started at the onset (explosion?). It would be too much coincidence I think to try to explain this with winds in several directions. I would apply Ockham's knife here, try to find the explanation with the least variables :)