APOD: A Twisted Meteor Trail Over Tenerife (2010 Jun 02)

[Gustavo]

Or it might be a zoom of the meteor superposed on the same picture so people could see it better.

[JLD]

Has anyone considered that the meteor, if an un-regular shape and is rotating, could actually be corkscrewing through the atmosphere? A corkscrew shape, viewed in 2D looks like the sine wave trail shown, if we assume say, a pear shaped object, the smaller end would burn off sooner, producing the wobble trail, as that part burns off the the meteor becomes a more regular, round ish shape as it travels, that would explain the wobble deteriorating and the trail turning into a regular trail. Just a thought

[apitko]

This image has been widely discussed in the meteoritics community. The consensus (unanimous as far as I've seen) is that the camera got jarred by wind or maybe an animal. The same effect has been seen on other images where that happened.

At first I thought, "Then wouldn't the stars be misaligned in the background too?" Then upon closer look, all the stars look like butterflies from obvious camera movement/shake. "The case has been sol-ved!"

[Dave Shaffer]

Unequivocal: it is camera shake!

I just downloaded the image. When I look at the EXIF data for the frame, it reports a 1 second exposure. Whether or not the camera was tracking, there should NOT BE ANY STAR TRAILING OR OTHER NON-LENS ARTIFACTS IN THE STAR IMAGES for such a short exposure UNLESS THE CAMERA MOVED.

[Chris Peterson]

Allow me to make a few physical observations, which might also address some earlier comments.

It is impossible to determine the direction of travel, rate of travel, distance, or entry angle. The light curve profile suggests that the meteor was traveling downwards in the image, but this is far from certain. We can use a few typical values to make some estimates about the meteor itself. A sporadic meteor with this brightness would typically be at a height of around 100 km. Given the high zenith angle, we can figure this meteor was approximately 400 km from the camera. It spans 7°, so for a typical 1-second event we have a velocity of 50 km/s, which is about what we'd expect. If the wiggle in the trail represents true motion of the meteoroid, we are looking at a peak-to-peak lateral position shift of about 1.8 km over a travel length of 4.8 km and a time of 100 ms. That strikes me as physically unrealistic.

The apparent magnitude in the image is about 4, but this was a 60-second exposure, so the actual apparent magnitude needs to be reduced by the exposure time difference. Assuming the meteor lasted one second, that brings its apparent magnitude to about zero. Its absolute magnitude, therefore, was about -3. That suggests a photometric mass of about 100 mg. For a typical bulk density of one, the expected meteoroid size is about 5 mm diameter. I can't think of any aerodynamic or electrostatic mechanisms that could cause such a small particle to oscillate laterally over hundreds or thousands of meters at ten cycles per second.

To summarize, I don't think it is possible we are seeing true motion of the meteoroid. That leaves two possibilities. One is that the camera moved. That happens all the time, for a variety of reasons, even in a well controlled setup. Other imagers have recorded meteors with similar trail shapes when they knew that the camera moved. The pattern of the meteor trail in this image even shows characteristics of damped harmonic motion- just as you'd expect if the camera was vibrating. That wouldn't necessarily be obvious in the stars- the exposure is long enough to show star trails, and the 8 mm fisheye lens introduces plenty of aberrations as well. A vibration lasting just a few seconds would probably not produce enough distortion of stars to be visible among the other aberrations.

The other possibility is that we aren't actually seeing the meteor at all, but its trail. If the meteoroid was very fast and very fluffy, it might have left a visible dust trail without being bright enough to leave much record on the camera. The dust trail, however, could persist for many seconds- a large percentage of the 60 second exposure- and that would be subject to wind movement. I've seen trails like that in images, and they normally show more blur than we see here. But it's not something I'd completely rule out.

[James Beauchamp]

I looked closer at the hi resolution image. A couple of things...

1. The visible amplitude is highest on the left of the trail, and appears to decrease linearly. If the camera was vibrating (translating into angular motion), it would be constant throughout the trail, so I'm going to discount that.

2. The trail is rather close to the horizon, meaning it has a significant amount of atmosphere to pass through. Note the stars near the trail, and the "fuzzy" amplitude they appear to have. Note also that the smearing is less at the edges, amost gaussian in nature. This is consitant with optical "shimmer" due to variability of air density in the optical path with respect to time. Add optical "shimmer" to the list.

3. Larger objects commonly exhibit asymmetric plasma trails. Even if the object were perfectly spherical, the minute amount of rotational inertia, combined with even a small asymmetric force (moment) and the extreme velocity would cause spin - very fast spin. So, I don't think rotational effects can be concretely ruled out. But a counter argument would be that if this was truly the size of a sand grain, one would expect low probability of asymmetric "burning", and the trail should be straight and/or homogenious.

4. Remember that plasma tends to act very strange compared to what we know of regular matter - especially in the conditions found at 60 km. Meteor fragmentation is common. If a piece breaks away, it may travel at a different velocity than the mother object, and therefore absorb energy at a different rate. Energy differential may translate into dramatic lower/higher propagation/dispersion velocity. I'm not even close to being a plasma expert (comments to the contrary from those who are are highly welcome!), but my caveman math brain thinks this could translate into a non-linear trail, consistant with #1 above.

5. (Again calling on the plasma experts) How much affect will a minute change of medium density have on plasma diffusion? If the meteor is passing through areas of larger and smaller density, and the ions are releasing at vastly different travel rates, wouldn't this also lead to the trail appearing to be sinusiodal?

[Chris Peterson]

I just downloaded the image. When I look at the EXIF data for the frame, it reports a 1 second exposure.

The EXIF data shows a 59-second exposure, which is consistent with the star trails seen in the central image.

[drollere]

This image has been widely discussed in the meteoritics community. The consensus (unanimous as far as I've seen) is that the camera got jarred by wind or maybe an animal. The same effect has been seen on other images where that happened.

That doesn't jive with larger bolides pretty much all observers have seen at one time or another in which such a "spiral" trail continues to expand with the same shape. Unless I was in the middle of a eye seizure, the resulting persistant trail shape supported that it was most likely rotating at a high angular velocity and burning asymetrically.

i agree. two points:

if you consider the second meteor photograph (linked from today's image), you see clearly that the oscillations are not uniform in period or in amplitude -- some are longer than the rest, the vibrations get larger then smaller then larger again, etc. it's very hard to produce that kind of pattern from a random bump on the equipment, wind blowing on the equipment, etc. ... a bump would produce a large initial and decaying amplitude, wind would produce aberrations in all the star images.

comparing the two photos, you see that the amplitude relative to the length is very similar, about a 1:4 ratio. if these were distortions caused by amospheric or kinetic disturbances, then you'd see more variance around the average path, depending on the energy of the disturbance -- a big bump would produce really wide oscillations.

these paths may resemble the magnus effect in high velocity rifle rounds.

[Pedro Leon]

A little eartquake at the moment of the photo ??

[DaveMorton]

Upon close examination of the image, one will see that there are NOT two meteors, as some have mentioned, but that the "larger" one is an inset magnification of the "smaller". Now, to my thinking, the shape of the trail indicates that the meteor was traveling from left to right, with the amplitude of the distortion generally diminishing over time. Also, the frequency of the distortion is rather chaotic, rather than smooth and regular. The distortion patterns of the stars also don't match the distortion of the trail, as only the brightest stars nearest the fish-eye's edge seem to be affected, rather than all of them. And, if you take the trail distortion along the direction of travel, and try to determine the possible angle of distortion from a shaking camera/tripod, and then try to match it up against the same derived angle from the star distortion, there is a marked (about 9 degrees, from what I could measure) difference, thus eliminating the camera/tripod as the source of distortion. Further, the trail's distortion is classically indicative of motion trails left by non-spherical objects which have complex (2 or more axis) rotations.

If I had to guess (and I do have to guess, since I'm not God, and don't know everything), I would say that the trail distortion was caused by the asymmetrical shape of the meteor, coupled with an axial spin and a slight tumble.

[Dave Shaffer]

I just downloaded the image. When I look at the EXIF data for the frame, it reports a 1 second exposure.

The EXIF data shows a 59-second exposure, which is consistent with the star trails seen in the central image.

I stand corrected - I used Canon's ZoomBrowser program first (which reported the 1 second). A different header viewing program does report 59 seconds.

I do agree with your comments about the size of track variations and can't imagine any forces due to pressure at such altitudes that could cause such accelerations: on the order of 1000g! (1 km/sec delta v in 0.1-0.2 seconds).

[Chris Peterson]

That doesn't jive with larger bolides pretty much all observers have seen at one time or another in which such a "spiral" trail continues to expand with the same shape. Unless I was in the middle of a eye seizure, the resulting persistant trail shape supported that it was most likely rotating at a high angular velocity and burning asymetrically.

We need to distinguish between the apparent path of a meteor, and the path made by the meteor trail. Meteors don't spiral or jig. Yes, I know there are anecdotal reports of such motion, but I don't believe they describe an actual motion. There are simpler explanations. Plasma and dust trails persist for seconds or minutes, and certainly move under the influence of wind, resulting in visible trails that can be quite similar to what is seen in this image.

Usually, long exposure images containing meteors just show the meteor itself, or they show a superposition of the meteor and the resultant dust/ion trail. The trail is smeared by the motion it makes over the exposure time. This image could be explained as a meteor trail if we assume that the actual meteor occurred a while before the shutter was opened, and all that was captured was a trail that was very slowly evolving (if it were evolving rapidly, it would blur in the one-minute exposure time).

If this image was part of a series with very little down time between exposures, the meteor ought to show on an earlier image, and the trail continue to show on later ones.

[charles wolf]

Did anyone else notice that there are two meteors in this image and they both have twisted trails? Unless it was one meteor that first ionized a path, and then didn't, and then did again...there were two meteors that had similar characteristics. I suppose that is possible if they both came from an original source, but the likelihood that they would both create similar (or seemingly identical) trails would be astronomical (wouldn't it?). Therefore I would suggest some kind of atmospheric occurance. Or some aberration of the photo equipment, stand, etc.

[gar37bic]

The shape of the trail seems consistent with a helical path, and it makes sense that a spinning asymmetrical object would be likely to do this. (This reminds me of that Russian rocket over Scandinavia that left the weird sky figure a month or two ago.[EDIT: Here's a youtube link: http://www.youtube.com/watch?v=TXA8WmFnp8s ])

Three observational techniques that I can think of could confirm helicity, unfortunately they all require very good luck to be in the right place at the right time with the right equipment.

• laser or radar tracking might be able to provide enough range precision to prove that the outermost parts of the trail would have slightly different distances than the center.
• Doppler analysis of the color spectrum of the trail could disclose the slightly different speeds at which the trail material is receding from and and approaching to the observer at different points in the trail. I doubt this could be done from a photograph. I would think it would depend on having a spectrograph looking at the right place at the right time. Perhaps if someone were to set up a watching station, having a telescope with a plate having an array of closely spaced holes small enough to get spectral lines at a large number of closely spaced locations (just as an astronomer I recently learned about, is using to watch for extra-solar planets) then eventually a track would pass over the observation field in such a way that different components of the 'helix' would be caught in different holes, and the Doppler effect on the spectra would show if there is a periodic oscillation in the speed toward and away from the observer, that would be 90 degrees out of phase with the 'horizontal' oscillation of the trail.
• The third method would be doable by a determined group of amateurs with the ability to control photography or filming with their computers. If by some fortuitous circumstance, the same trail were photographed or filmed from two or more different locations in such a way that the two photographs or motion sequences could be synced together reliably, then by triangulation the full 3D extent of the trail could be determined. This might be accomplished by several (two or more) observers who are separated by a significant but not too large distance, who agreed on a common observation schedule. Ideally the photographs or films (or digital movies, of course - probably best and easiest) could be automatically synchronized via the internet. These observers need not be 'aimed' at exactly the same part of the sky, so long as there is sufficient overlap. So a group of several observers could put together a kind of "poor man's interferometer" for this purpose, having as many observing elements as desired and a field width that depended on the number of observers available. The relatively low speed of the meteor track would allow a successful joint observation with a time jitter of as much as a second or two, which is achievable if all parties' controllers are synced using the Network Time Protocol (NTP) (all modern operating systems support NTP but I don't know about the camera control capabilities).

[gpronger]

My first question would be can we determine whether it may be a piece of space debris, which would likely be significantly more asymmetric than a meteorite.

[TLM]

I have seen a meteorite spiral in, it was the most amazing thing I have ever seen. I swear I could hear it whistle! It looked a lot like the photo, only it had a bigger spiral and didn't flatten out before it exploded. It was very green in color. I live in Central Idaho in a place with very few lights, so we can see the sky very well. I did not write down the date it happened, but it was in 2000 or 2001.

[Geister]

I think it could be attributed to some kind of turbulence. Just like eddies affect the path of airplanes, some form of turbulence has to exist up there too that could affect not only the path of the meteor but also the path of its trail. Thermals disrupt the airflow of the wind creating eddies, afaik. Since there is some kind of wind blowing out there, why couldn't it have turbulence too caused by some higher density or whatever it is made of?

[James Beauchamp]

I just downloaded the image. When I look at the EXIF data for the frame, it reports a 1 second exposure.

The EXIF data shows a 59-second exposure, which is consistent with the star trails seen in the central image.

I stand corrected - I used Canon's ZoomBrowser program first (which reported the 1 second). A different header viewing program does report 59 seconds.

I do agree with your comments about the size of track variations and can't imagine any forces due to pressure at such altitudes that could cause such accelerations: on the order of 1000g! (1 km/sec delta v in 0.1-0.2 seconds).

I'll "third" the physics angle (pardon the pun). It just goes against common sense.

That's why I went for the optics and plasma ideas. Thanks for the reply.

[Jim Harwood]

A key to the photo is close examination of the two streak images. They are identical except for scale, down to the oscillation details and the short break at the right end. Now carefully examine and compare the star patterns around each streak. They are identical. One image is a replica of the other. Finally, compare the bottom half of the whole image with the top half. Notice the bottom half includes the Milky Way, which is cut off at a boundary that runs horizontally through the image. The big image of the streak must have been overlaid onto the original photo to magnify the streak, but this fact was not given us, creating more confusion. The cause of the oscillations? Possibly shutter vibration upon opening, or other local impulse vibration. The magnified image blur of the stars reflects this in direction and magnitude. If the meteor were ablating asymmetrically, its brightness would change significantly with its rotation. Not observed.

[alankennedy]

I've seen a trail bounce ,zig-zag and break up in the space of about three to four seconds;
looked like a classic bounce and drag against the atmosphere diagram
then I read the bit about camera variations and the image I'd imagined of a turbulent tail vanished -

[BMAONE23]

Did anyone else notice that there are two meteors in this image and they both have twisted trails? Unless it was one meteor that first ionized a path, and then didn't, and then did again...there were two meteors that had similar characteristics. I suppose that is possible if they both came from an original source, but the likelihood that they would both create similar (or seemingly identical) trails would be astronomical (wouldn't it?). Therefore I would suggest some kind of atmospheric occurance. Or some aberration of the photo equipment, stand, etc.

The trail depicted in the upper left corner is an enlarged inset image crop of the lower right portion containing the actual trail

[geckzilla]

What kind of aberrations are usually present in photos taken by lenses like this? What I see in the stars are two things: Star trails themselves, which are the bright, short lines, and a fainter, somewhat oval trail surrounding them, particularly apparent near the right edge. The fainter trails would seem to indicate camera shake. I'm unfamiliar with light distortions for this type of lens or other things which could have caused the fainter trails, though.

[jenius]

Looks like dampening vibration caused by camera shake. Notice symmetrical blur marks around star images.

I agree with Dr. Olman - the blur around the star images would indicated damped camera shake.

However, ICBM designers can make their RVs weave, using relatively simple aerodynamics, so that the RVs are more difficult to intercept. A weaving RV would probably look like what you see here...

[zumzoom0]

how about a rocket part like a long cylinder. . .

[Sagian2005]

I don't think it was 'camera shake'. A deviation on the order of arc-seconds would show up in the stars, especially in the inset.

My first question would be: Which end is the tail? Did it enter the atmosphere and somehow acquire angular momentum, or was it already spinning and somehow lose angular momentum?