Damped sinusoid meteor

[bobbyf]

During the ASSA Alpana Astrocamp, I managed to capture the start of a meteor hitting our atmosphere.
At the time I remember seeing it and thought I may have caught it.
When I reviewed the image at home, I noticed that the start looked wobbly and so I stretched it a bit and zoomed in to see an oscillation, which appears to dampen into a straight line.
At first i thought I'd knocked the camera, but the stars are OK.
Is this commonly understood to occur and seen regularly in images?
I've never seen or heard of this effect before.
Cheers

I was doing high ISO, short exposures at the time, getting position and focus right, hence the noise :(
Regards

Bob
Equipment used was an old 200mm F4 Nikkor lens on a Nikon D7000.

[speach]

When it first entered the atmosphere it wasn't round, so you would get a wobble then as it got further in the heat would burn off the projections and it would become round, the track would then settle down and not wobble. May be that's the answer.

[RB]

You initially bumped the camera which registered the wobble but the stars/background hadn't registered yet on the long exposure.
Then the camera settled and you got the nice stars/background with a straight path for the rest of the meteor path.

:)

[bobbyf]

Thinking about it, the camera was well fixed, piggy backed on my scope on my NEQ6, using a timer and the brighter stars around M20 are round, so I'm pretty sure the dampening effect is real.



Sounds plausible.
Cheers
Bob

[Peter Ward]

Doesn't look like a meteor trail to me...there is no rapid ramp up in brightness or trailing off in intensity toward the end of the burn up.

Bright Low Earth Orbit object + bump seems more likely.

[Tony_]

Apparently it has happened before and here is an explanation from APOD:

Explanation: Did this meteor leave a twisting path? Evidently. Meteor trains (http://apod.nasa.gov/apod/ap011130.html) that twist noticeably are rare - and even more rarely photographed - but have been noted before (http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003ChA%26A..27.. 435G). The underlying reason for unusual meteor trains (http://apod.nasa.gov/apod/ap981127.html) is that many meteors are markedly non-spherical in shape and non-uniform in composition. Meteors, usually sand sized grains that originate in comets, will disintegrate as they enter the Earth's atmosphere (http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html). Non-uniform meteors (http://www.nineplanets.org/meteorites.html) may evaporate more on one side than another. This may cause a rotating meteor (http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004AGUFMSH51D029 5K) to wobble slightly in its path, and also to spray fast moving debris (http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998JIMO...26..22 0S) in a nearly spiral path. The fast moving meteor debris ionizes molecules in the Earth's atmosphere that subsequently glow (http://apod.nasa.gov/apod/ap020816.html) when they reacquire electrons (http://www.aip.org/history/electron/). Surely no meteor is perfectly uniform and spherical, so that a slight swagger that is below perceptibility is likely typical. Meteors may well have seeded Earth (http://antwrp.gsfc.nasa.gov/apod/image/0208/earthlights02_dmsp_big.jpg) with the prebiotic molecules (http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002AstHe..95..51 5A%3Eorganic%20materials%3C/a%3E%20and%20%3Ca%20href=) that allowed for the development of life (http://en.wikipedia.org/wiki/Timeline_of_evolution).

[bobbyf]

Thanks for that Tony.
I've checked the image details and it was a 30 sec exposure at ISO 4000, so any bump would have captured movement in the brighter stars in the image for sure.
It's quite exciting really, to think that I may have captured something that not many people have managed to.
I am convinced that it is real movement of the meteor, and what you and speach have suggested certainly seems to be the best explanation that I have heard or read about to date.
Thanks again

Bob

[bkm2304]

Can't agree that it's a spiralling meteor explanation for the following reasons:

1. Look at the deviations from the straight line. If the meteor is say, 70km up when it hits the air, then the fact that you can actually see the deviations makes them deviations of many kilometres. Given that this meteor vaporised quickly, then it is likely to be no more than small pebble or sand grain size.

2. After deviating so many km, it then does a series of very, very sharp turns before straightening out. What forces are acting upon a very small piece of rock no more than a few grams in weight at best, to cause this?

3. If we are actually observing the rotation of the meteor then, as per 1,the thing is at least several km wide! Consider what you are seeing in the pic then consider the angular size in arc seconds at that distance and the object must be massive. if it were so then it would have ploughed into the Earth and made a serious mess.

4. I agree with Peter that you are looking at a satellite as it has no ramp up of light as photographic meteors typically have- this thing just appears, turns 90 degrees at least several times then straightens out with no apparent loss of luminance - if it was a meteor it would have hit the earth a few seconds later.

Richard

[bkm2304]

Here's a pic of what meteors do (http://www.iceinspace.com.au/forum/showthread.php?t=138044&highlight=Meteor) when they hit the air

[bobbyf]

Thanks Richard
Yep, i've captured meteors before (albeit not as good as the linked image, which is awesome :thumbsup:) but they've always been widefield images at 10 or 18mm, not the 200mm that this one was, so i didnt know whether it was normal and simply not normally seen.
I definately remember seeing it at the time and never once thought it was a satellite, but i could be wrong.
It was only visible for a short period of time (1-2 secs) and was travelling much faster than i would expect satellites to travel.
Intriguing
Cheers
Bob