The Corkscrew Meteor

startleman writes "Over on Space.com is an interesting image of a corkscrew meteor. 'On Jan. 1, 1986, [Jimmy Westlake] was photographing [Halley's comet] through his homemade 8-inch reflecting telescope..."About one minute into the exposure, I watched a meteor zip through the field of the telescope." When he developed the roll of slide film, he was astounded that '...Crossing the tail of Halley's comet was a corkscrew meteor trail with no fewer than 25 twists in it.' Westlake's photo was never published until today. He wonders if there are others out there."

Comments

Hmm

[PrvtBurrito]

Although I have never seen it in a photograph, couldn't this have been caused by visual waves caused by the atmosphere? Anyone who has looked through a telescope in (crappy) skies knows that objects appear to oscillate rapidly. I don't doubt that a meteor could travel in such a way as to pick up on this. The reason the stars don't appear in this way is because they are fixed objects in a time lapse photo and are averages of all the waves. -Sean

Re:Hmm

[Theory of Everything]

Although I have never seen it in a photograph, couldn't this have been caused by visual waves caused by the atmosphere?

I believe that you may almost be on to something. IAAA (I Am An Astronomer) and the "visual waves" you speak of are called "seeing"--atmospheric turbulence tends to blur out the images of stars. Though stars are generally sized 1/1000 of an arcsecond (the largest is about 50/1000), the atmosphere blurs on a scale of a few arcseconds. So if the "corkscrew" were caused by seeing, one would expect the stars to be blurred by an amount similar to the amplitude of the "corkscrew", which we do see in the image.

However, seeing (turbulence) is random. The "corkscrew" is clearly not--it appears sinusoidal. A much more likely explaination is that the telescope mount is vibrating--this would cause sinusoidal smearing of all objects in the field. the meteor, which is moving, becomes a corkscrew; the stationary stars get smeared in the direction of the vibration (as is seen in the picture). The meteor appears about 1 minute into the "2 minute exposure", and has "25 corkscrews", so the vibration is at about a half a hertz. Thus it is likely that his mount wasn't quite sturdy enough for the 'scope, or winds were abnormally high that night. Alternatively, since he apparently accounts for sidereal motion (the telescope has electronic drives to track stars, compensating for the earth's rotation), maybe the drive motors have noise at half a hertz....

Re:Hmm

[Some guy named Chris]

The meteor appears about 1 minute into the exposure, but it doesn't take 1 minute for the meteor to cross the field of exposure, which is what you are implying by your "half a hertz" oscillation theory.

Now, the motors could have had a 60 hertz "hum" and the meteor was in the frame for just under half a second. That cycle rate is common for AC in North America, and I can belive a meteor streaking across the sky in half a second more than I can believe it streaked across the sky in a whole minute.

Re:Hmm

[Almost-Retired]

With all due respect to all the theories being tossed otu as 'obvious facts', but which given the time frame cannot be, let me throw out another theory that fits the evidence a lot better than gearing errors in the scope mount or wind induced vibrations, considering that the meteor probably went across the field of view in 3 seconds or less.

How about if the meteor itself was spinning? Would this not tend to create the effect shown? These things are not always made out of uniform material, and aren't often nice and convieniently round.

Given the time frame of the observation, its the only thing that makes any sense to me.

--
Cheers, Gene

Re:Hmm

[helioquake]

Gene, your explanation is unlikely.

The light of a meteor originates from super-heated plasma that forms in front of a meteor, as it drags through air at a high speed. It is not a part of a meteor body itself that is glowing and spinning as it run across the sky.

Besides, these meteors (that disintegrates) are very small (less than an inch). I doubt that we would see any significant sign of spinning if it is so small (the oscillation amplitude of the contrail can imply the scale size of a meteor, which must be huge if it is indeed a spinning rock shown in the photo).

The killer evidence, to me, is that the direction of blur shown in the field stars is aligned with the motion of the wobbly contrail of the meteor. Its oscillatory amplitude declines as it passes, also. That may be a signature of vibration dumping in the support mount of the camera.

I've read a part of Camille Flammarion before. He's an interesting observer (and a very literate one at that). But I won't take his drawing in his book as always accurate.

Re:Hmm

[fenris_23]

The stars appear smeared in the direction of oscillations yet not the comet. Should the comet not also be smeared in that direction?

Also, with no vibrations, should not the stars be smeared in the opposite direction of the Earth's rotation? If so - and if the distance of their smears roughly corresponds to the distance at which they should travel across the sky in two minutes (I am not certain that they would travel that far however) - then the vibration theory could be discounted.

Also note that the amplitudes are not uniform. If the object was indeed traveling in some sort of cork-screw fashion, then it would seem likely that from most vantage points, the amplitudes would increase and decrease; unless the camera was positioned such that it pointed perpendicular to the comets trajectory.

And then by the same reasoning, the frequency should appear to decrease as the object approaches. But the frequency seems to stay uniform.

This is a weird photo.

Lost a chuck, and is wobbling?

[abulafia]

I'd guess a piece of it fell off/vaporized (nonuniform portion, etc.), and it is wobbling around its axis as it spins.

But what do I know, IANAA(stronomer).

by the way...Comet Macholz

[helioquake]

Off topic but...Comet Macholz is found right by Pleiades ("seven" star cluster) tonight. I could manage to spot it with a pair of binocular in Boston. It's fairly fuzzy and faint, though.

Re:Woobly Telescope

[node 3]

It looks like all the backround stars have some motion blur.

You think the stars have motion blur, look at the meteor!

The motion blur of the stars is due to their movement across the sky during the exposure (like also happened with the meteor).

Re:Woobly Telescope

[Stoutlimb]

I think you are right. When I looked closer at the stars, they seemed motion blurred, but in an elliptical shape. This would happen if the telescope was vibrating back and forth, in one direction. Perhaps if the telescope was on the back of a pickup truck or something we would see this.

When you look at the wavy meteorite trail, it's not a perfect sine wave. It looks like it was "waving" on an axis that wasn't perpendicular to the direction of travel. In fact, the apparent direction of the waving seems to line up with the stars motion blur. It seems the axis of vibration is rotated twenty or thirty degrees counterclockwise from the direction of the meteor. Because the stars shape and the wave of the meteor are the same, I'm inclined to agree that this is some kind of vibrational anomoly.

What do you guys think?

Re:Just a guess, but yes there's more.

[JabberWokky]

Um... I think you misread.

The question is: Are there more photos of this out there?

--
Evan "And I believe the assumption is 'taken by humans', just in case you leap to assumptions again"

I've seen these.

[Anonymous Coward]

I've seen meteors do this, with naked-eye observations during one of the more active fall showers a few years ago. In fact, most of the larger or brighter ones seemed to do it with varying intensity. It's not atmospheric distortion. It's way too periodic.

I've also seen them with second or third order oscillations, making larger spirals like a big, fast, heavy leaf 'fluttering' to the ground.

I just assumed that it was the meteor tumbling like it's probably going to - considering it's not probably not an aerodynamically stable shape - and just spewing and sputtering ablating matter as it burned up.

Why is this a mystery? Anyone that's shot irregular flakes of rocks (or, say, pennies) out of a wrist-rocket or slingshot will see that they behave in much the same way - aerodynamically unstable objects tumbling and spinning from drag as they pass through the atmosphere at high speed.

Re:Woobly Telescope

[khrtt]

When you look at the wavy meteorite trail, it's not a perfect sine wave.

Perhaps the meteor has a highly irregular elongated shape, and reflects light unevenly as it rotates, producing the irregular trail.

I have seen one

[Anonymous Coward]

With the naked eye. I was spending the night at Santa Cruz island, Channel Islands, California. It was in November and we had sailed out there to spend the night. It was very clear that night and dark. No city light (I live in Los Angeles). You could see the Milky Way. Then my friend and I noticed little metior streaks, kinda nice. The I saw this large one, it wasn't the line flash you see all the time. This was slower moving and corkscrew. It traveled across the sky and the trail glowed for a few seconds. I though it was something that happens all the time.

Yes, indeed

[barakn]

The assumption of a 60 Hz hum and 25 twists implies a total visible travel time of .42 seconds, which seems about right. The fact that the trail isn't more smeared is an indication that the meteor trail is made by a swiftly moving light source that would look like, if we could have taken a very short duration exposure, more like a point source than a bright coma followed by a tail of brightly glowing plasma. The roughly constant production of light along the trajectory and its length suggests that the meteor was a so-called "earth-grazer" (not to be confused with asteroids or comets of the same name) dumping most of its kinetic energy rather high in the atmosphere along an almost horizontal path. Somebody with more time on their hands than I could develop an algorithm, using simple and fairly reliable assumptions (a straight trajectory at at a slowly decelerating velocity, damped sinusoidal oscillation, etc.) to extract a third dimension of information from the photo. In other words, a crude movie of the meteor moving across a backdrop of comet and stars could be made. I find this encoding of an extra dimension on a flat piece of film intriguing. It reminds me of holograms, although they of course encode an extra spacial, not temporal, dimension.