APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

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APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by APOD Robot » Mon Sep 05, 2016 4:10 am

Image Spiral Meteor through the Heart Nebula

Explanation: What is this meteor doing? Dynamically, the unusually short and asymmetric train may indicate that the sand-sized grain at the center of the glow is momentarily spinning as it ablates, causing its path to be slightly spiral. Geographically, the meteor appears to be going through the Heart Nebula, although really it is in Earth's atmosphere and so is about one quadrillion times closer. Taken last month on the night of the peak, this meteor is likely from the Perseid meteor shower. The Perseids radiant, in the constellation of Perseus, is off the frame to the upper right, toward the direction that the meteor streak is pointing. The Heart Nebula was imaged in 18 one-minute exposures, of which the unusual meteor streak appeared on just one. The meteor train is multicolored as its glow emanates from different elements in the heated gas.

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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by Mactavish » Mon Sep 05, 2016 4:38 am

How is it determined that the meteor is the size of a grain of sand? Just curious.

heehaw

Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by heehaw » Mon Sep 05, 2016 8:57 am

Mactavish wrote:How is it determined that the meteor is the size of a grain of sand? Just curious.
http://www.amsmeteors.org/meteor-showers/meteor-faq/#3

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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by alter-ego » Mon Sep 05, 2016 7:09 pm

heehaw wrote:
Mactavish wrote:How is it determined that the meteor is the size of a grain of sand? Just curious.
http://www.amsmeteors.org/meteor-showers/meteor-faq/#3
Radar measurements and single-body ablation models have contributed to characterizing meteor mass entering the Earth's atmosphere. Although complicated, the method does yield mass estimates based on observations during entry. It's reasonable given a mass and material knowledge, estimating size is pretty straightforward.
The Geminid meteor shower during the ECOMA sounding campaign: specular and head echo radar observations wrote:...However,one essential point deriving absolute meteor fluxes is to estimate the particle size range of the observed particles. This particle size range was determined by applying the method as described in Stober et al. (2011) using a single body meteor ablation model. In a first step the meteoroid mass is inferred at the specular point by solving the equations of single body meteor ablation using all the measured parameters (e.g. electron line density, altitude, entry angle, velocity). By solving the model equations we compute the meteoroid deceleration, the meteoroid surface temperature and the meteoroid particle mass at this stage of its flight path. The upper atmospheric properties of the meteors are inferred by performing a backward integration. The Geminid upper atmospheric meteoroid mass was in the range of 3×10−3–10−5 g at both radar sites. The 10−5 g represents the lower mass limit to be detected by the system for Geminid entry velocity.
Edit: And by analyzing micro-craters in substrates returned from space missions :)
Last edited by alter-ego on Mon Sep 05, 2016 8:27 pm, edited 1 time in total.
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by Boomer12k » Mon Sep 05, 2016 7:33 pm

"Shot through the heart...and you're to blame...."

Great piece of happenstance....nice shot.

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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by Chris Peterson » Mon Sep 05, 2016 9:48 pm

APOD Robot wrote:Image Spiral Meteor through the Heart Nebula

Explanation: What is this meteor doing? Dynamically, the unusually short and asymmetric train may indicate that the sand-sized grain at the center of the glow is momentarily spinning as it ablates, causing its path to be slightly spiral.
There is little or no evidence that meteors wiggle or spiral. In this image, the path is perfectly straight. It was a long exposure with a meteor in the middle. Almost certainly, what we're seeing is the instant of the trail, and the much longer period of ionized gas blowing around, in different directions at different altitudes (very commonly seen in meteor trains). (The 2005 image doesn't show a wiggling meteor, either, but rather a wiggling optical system.)
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by MarkBour » Mon Sep 05, 2016 10:17 pm

Exceptionally beautiful track! Would you say there is a time-progression of color from red to yellow to green, back to red, as it disintegrates? But the yellow is still going strong in the middle of the track as the green peaks. (If I understand what Chris just posted, the green may have appeared after the meteor was done burning, but a left-over phenomenon in the same region as the yellow streak in the middle.) What accounts for the various colors? Did the meteor actually distribute material in a shape to make the spiral, like a spinning pinwheel firework?
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by Chris Peterson » Mon Sep 05, 2016 10:50 pm

MarkBour wrote:(If I understand what Chris just posted, the green may have appeared after the meteor was done burning, but a left-over phenomenon in the same region as the yellow streak in the middle.) What accounts for the various colors? Did the meteor actually distribute material in a shape to make the spiral, like a spinning pinwheel firework?
Not only was the meteoroid not spiraling, neither is the meteor train we see here. It's an illusion. As the meteor descends through the atmosphere, it encounters winds moving in different directions. That wind tears a persistent train in different directions. Most likely we're just seeing a transition in the middle of the train between winds blowing one way and winds blowing nearly opposite (not an uncommon occurrence). That split the train. The particular wind gradient is fooling us into thinking we're seeing a spiral pattern.

The image was made with a Bayer matrix sensor designed for terrestrial photography, so there are issues with color accuracy when viewing emission line spectra. But color shifts in descending meteors are common, created by a combination of different materials ablating (with refractory elements burning deeper in the atmosphere, at higher temperatures) and different conditions of the atmosphere around the meteoroid.
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by Craig M. » Tue Sep 06, 2016 12:52 am

A quadrillion times closer? I hate that nonsensical form of comparison! 1,000,000,000,000,000 x what? What is so hard about expressing it correctly and accurately: one quadrillionth as distant?

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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by Chris Peterson » Tue Sep 06, 2016 1:02 am

Craig M. wrote:A quadrillion times closer? I hate that nonsensical form of comparison! 1,000,000,000,000,000 x what? What is so hard about expressing it correctly and accurately: one quadrillionth as distant?
And yet... the term used is unambiguously understandable, whereas the term you suggest is less commonly used and therefore trickier for most people to parse.
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by geckzilla » Tue Sep 06, 2016 5:34 am

Chris Peterson wrote:
APOD Robot wrote:Image Spiral Meteor through the Heart Nebula

Explanation: What is this meteor doing? Dynamically, the unusually short and asymmetric train may indicate that the sand-sized grain at the center of the glow is momentarily spinning as it ablates, causing its path to be slightly spiral.
There is little or no evidence that meteors wiggle or spiral. In this image, the path is perfectly straight. It was a long exposure with a meteor in the middle. Almost certainly, what we're seeing is the instant of the trail, and the much longer period of ionized gas blowing around, in different directions at different altitudes (very commonly seen in meteor trains). (The 2005 image doesn't show a wiggling meteor, either, but rather a wiggling optical system.)
I've been dubious about the "spiraling" meteor imagery, myself. When I question it, though, the photographer will swear their system was motionless and that the meteorite must be spiraling.
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by Chris Peterson » Tue Sep 06, 2016 1:49 pm

geckzilla wrote:I've been dubious about the "spiraling" meteor imagery, myself. When I question it, though, the photographer will swear their system was motionless and that the meteorite must be spiraling.
Yeah. But even the best small telescopes and camera mounts wiggle. Photographers are seldom aware of this, because it all averages out into a very small increase in stellar diameters, largely indistinguishable from seeing effects. It is only apparent when something fast happens, like a meteor. You can also see it by stopping tracking, allowing stars to trail. At spots along the star tracks little wiggles show up- wind gusts, earthquakes, trucks on the highway- hard to know what, but lots of things can drive brief resonances in a mechanical system. Harmless for normal imaging, but quite startling with a meteor.

Dynamically, if you work out the forces that a meteoroid would experience spiraling or wiggling enough to be seen on an image, there's no way the particle would survive. Today's image, of course, doesn't show a hint of spiral or wiggle in the meteor, only the unsubstantiated suggestion that the shape of the train material is somehow caused by the rotation of the meteoroid- unlikely or even impossible. (Not the rotation of the particle- that can certainly happen; just the notion that the shape of the train is impacted by that.)
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by MarkBour » Tue Sep 06, 2016 3:03 pm

Chris Peterson wrote:As the meteor descends through the atmosphere, it encounters winds moving in different directions. That wind tears a persistent train in different directions. Most likely we're just seeing a transition in the middle of the train between winds blowing one way and winds blowing nearly opposite (not an uncommon occurrence). That split the train. The particular wind gradient is fooling us into thinking we're seeing a spiral pattern.
Thanks for the clarification. Is the green color in this persistent train likely produced by about the same process as in a green aurora ... oxygen transitioning back from an excited state? Can you tell from this image anything about the actual length of the train (e.g. to be specific, from the beginning to the end of the green region), its distance from the camera, and the speed of the meteor?
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by DavidLeodis » Tue Sep 06, 2016 7:22 pm

I would be grateful if someone could please clarify if the quadrillion in the explanation is the 1015 or the 1024 definition of a quadrillion.

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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by Chris Peterson » Tue Sep 06, 2016 7:30 pm

DavidLeodis wrote:I would be grateful if someone could please clarify if the quadrillion in the explanation is the 1015 or the 1024 definition of a quadrillion.
Since this is an American site sponsored by an American agency edited by American astronomers, I think you can safely assume "quadrillion" means 1015. (Which is quite close to being correct, given a meteor 100 km away and the nebula 7500 ly away.)
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by Chris Peterson » Tue Sep 06, 2016 7:38 pm

MarkBour wrote:
Chris Peterson wrote:As the meteor descends through the atmosphere, it encounters winds moving in different directions. That wind tears a persistent train in different directions. Most likely we're just seeing a transition in the middle of the train between winds blowing one way and winds blowing nearly opposite (not an uncommon occurrence). That split the train. The particular wind gradient is fooling us into thinking we're seeing a spiral pattern.
Thanks for the clarification. Is the green color in this persistent train likely produced by about the same process as in a green aurora ... oxygen transitioning back from an excited state? Can you tell from this image anything about the actual length of the train (e.g. to be specific, from the beginning to the end of the green region), its distance from the camera, and the speed of the meteor?
The colors are formed from one or more narrow emission bands. It is particularly difficult with the broadband filters used to create the image to tell just what those lines are, however. It would be possible to do some quantitative analysis on the trail here. If we assume it's a Perseid, and we know where the trail is observed, we can estimate its starting and ending height as well as the time it was luminous. We have a clue to its brightness (although the long exposure damages that data somewhat- a lot if the trail is saturated), which can be converted to photometric mass and ultimately an estimate of particle mass and size. Put all of that together and some of the colors can probably be explained.
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Re: APOD: Spiral Meteor through the Heart Nebula (2016 Sep 05)

Post by DavidLeodis » Tue Sep 06, 2016 7:50 pm

Chris Peterson wrote:
DavidLeodis wrote:I would be grateful if someone could please clarify if the quadrillion in the explanation is the 1015 or the 1024 definition of a quadrillion.
Since this is an American site sponsored by an American agency edited by American astronomers, I think you can safely assume "quadrillion" means 1015. (Which is quite close to being correct, given a meteor 100 km away and the nebula 7500 ly away.)
Thanks for that very quick response Chris :).

I thought it would likely be the 1015 but I was unsure.