British Astronomical Association
Supporting amateur astronomers since 1890

Secondary menu

Main menu

Home Forums Meteors
Terms of use

Fading Meteors

22 posts / 0 new
Last post
BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Fading Meteors

Hi,

The latest higher sensitivity WATEC cameras (the 910's) have began to show meteors in a slightly new way.

Video observing shows a wide variety of effects, some meteors seem to flash into then out of existence whereas other are much slower. Recently, though, I've started to notice some that positively ooze out of existance. I'm sure these have always been there but the better performance of the new cameras gives a much better view of the effect.

I've put a recent capture on youtube at https://www.youtube.com/watch?v=-thc7_H4F6c

The meteor can seen to elongate and fade away. I've not processed it yet, but last night I captured another one that was so slow the video capture software stopped recording before it finally disappeared from view when it fell below the threshold of the motion filter.

I imagine there is a confluence of material properties and orbital parameters that causes the effect on a propotion of meteors. There is also the effect of double brightness peaking meteors. The video shows this effect too by co-incidence. This has been the subject of previous professional research but that was on a relatively small sample. I've already received information from other video observers who have kindly sent me some of their images. Definitely another interesting feature to explore.

Even after a decade of video observing there's still new things to see!

Cheers,

Bill.

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
A slow fade to oblivion.

A slow fade to oblivion.

https://youtu.be/rKEydn4lTZ8

Cheers,

Bill.

Grant Privett's picture
Offline
Last seen: 11 hours 14 min ago
Joined: 28/12/2014 - 18:30
Fade to grey

Is the camera doing any running stacking of the images in the background?

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Hi,

Hi,

The 910 can do all sorts of onboard processing and summing but I just run them at the standard single exposure video rate.

Cheers,

Bill.

Grant Privett's picture
Offline
Last seen: 11 hours 14 min ago
Joined: 28/12/2014 - 18:30
Fade to grey

There goes that theory :)

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Hi Grant,

Hi Grant,

Perhaps not....

Whilst I haven't "set" any parameters it might not necessarily mean that something I don't know about may be going on. It'll be interesting to double check just in case (As or when I ever get to see the sky again. Apart from some very short windows all it has done here is rain for week after week. Very depressing) :-( 

However as a more quantative look at the fade here is a light curve I made of the first one I reported. The rapid onset is quite typical but the slower decay is clearly seen. As commented, this particular meteor is also one of the multi brightness peak class that occur.

cheers,

Bill.

D A Dunn's picture
Offline
Last seen: 23 hours 56 min ago
Joined: 04/03/2014 - 21:01
Software

Bill,

What SW do you use to plot the meteor intensity curve.

Many thanks

David D

Grant Privett's picture
Offline
Last seen: 11 hours 14 min ago
Joined: 28/12/2014 - 18:30
Fade to grey

Silly question: is the sensor interlaced and was a dark frame subtraction applied?

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
David,

David,

The curve is generated very crudely with the "slice" function in iris. This is then saved as a text file with the relative intensities.

It is then dropped into either excel for a quick look, like this, or GNUplot for a more upmarket finish.

Grant,

Yes, the devices are interlaced. this is what generates the spikey appearence as the meteor moves.

And, no there is no dark subtraction. At video rates the noise level is already quite low so I've never bothered with it. The real problem is good flat fielding. That's a different challenge!

cheers,

Bill.

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Hi,

Hi,

Caught yet another "melting meteor". These are definitley a subclass of meteoroid. The "fluffy dustballs"!

https://www.youtube.com/watch?v=eppOe5sJymk

Cheers

Bill.

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Hi,

Hi,

Here's a light curve generated from the latest "melting meteor".

Interesting to compare this one to the one above. Maybe I should have drawn a longer "tail" on this one to make the comparison more direct. However one can see the same gentle tail off of light as the meteor disintegrates.

I'll need to dig out some comparable brightness "regular" meteors to show how they have a steeper fall of of light, it's on the to-do list... ;-)

cheers,

Bill.

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Hi,

Hi,

As promised... Captured another "slow fade" meteor and also another bright meteor to compare it to.

These were both caught with the same camera system on the same calendar day. (One was from the morning and the other early evening.)

Fading meteor composite image.

Fading meteor light curve
.

Comparison meteor composite image.

Comparison meteor light curve.

By using the slice function in IRIS smoothed curves were plotted showing the light curves.

Axes are simply x:pixel and y:rel intensity

It can be seen the onset is very similar, then the mechanics come into play. The ablation characteristics change and the meteors "burn out" quite differently.

The graphs show the more rapid decline of the comparison and the slower decline of the fading meteor, nice to see a measureable difference.

cheers,

Bill.

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Hi,

Hi,

Whilst reviewing the video's from the last clear night I noticed one, that whilst not quite in the fading class, did appear somewhat unusual.

It looked like it was varying throughout it's trajectory. Having watched the video several times I was convinced it was a real effect.

However when using the usual slice function all of the scan line artifacts pollute the image...

Not very pretty. But doing the Bezier smoothing on the graph reveals the effect quite clearly...

Working with the other meteor observers in the NEMETODE group has turned up quite a few double peaked meteor but I've never seen a meteor with this number of "peaks". There are five definite "peaks" (and possibly another very weak one but the smoothing might be playing tricks here.)

Another interesting capture.

cheers,

Bill.

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Hi,

Hi,

Here's the light curve from meteor 20160924_232416 (and a spectrum). Light curve shows the distinct shape as illustrated in previous postings. Now just need more spectra to see if what the compositional traits are (orbits would be nice to see of it's fluffy cometary stuff...)

Here's the capture image that shows the zero order image plus weak spectrum.

...and the smoothed light curve with the distinctive looking tail off like the other example.

...also the spectra again, just in case...

it's all good stuff... ;-)

cheers,

Bill.

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
The fading meteors continue

The fading meteors continue to be captured...

Got this last week. https://www.youtube.com/watch?v=YrxxiWbe40Q

First time I've seen this effect, most unusual.

cheers,

Bill.

Jeremy's picture
Offline
Last seen: 16 min 30 sec ago
Joined: 04/03/2014 - 22:00
Separating Meteor

That's a remarkable video, Bill. Certainly looks like the meteor separates.

Jeremy

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Hi,

Hi,

Thanks, I initially wondered if this effect is what I have picked up in the more unusual spectra that show changes towards the end of flight.

...but perhaps not...I've been doing some crude velocity measurements and the separating part is travelling at more or less the same velocity (until burn out) as the pre separating meteor trail. So it looks like the meteoroid "sheds" some material, perhaps volatiles reaching a critical temperature and then taking some portion meteorid with it giving the little "puff" of stuff.

A spectrum would have been nice but it's really nice to catch a new meteor ablation effect (unless anyone else has recorded it before...)

cheers,

Bill.

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
One observation is an oddity

One observation is an oddity but two is the discovery of a previously un-noted class of meteor behaviour!

Caught a second separating meteor this morning. Fascinating. Having viewed several hundred video's there a a few suspicious ones but this and the previous are by far the most definite.

https://www.youtube.com/watch?v=q59X2xWLGao

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
These "dissolving" meteors

These "dissolving" meteors are proving to be fascinating...

In an attempt to better visualise the unusual ablation I've mounted 25mm lenses on a couple of cameras to give a larger image scale Unfortunately the corollary is a smaller field of view though ;-(

However caught this near perfect example of a melting meteor this morning.

https://youtu.be/cvOFgU8CFIA

The meteoroid must be fragmenting into a large number of extremely small particles to exhibit this behaviour. Even at this size they are still undergoing very rapid heating and evaporation. Just melting into the atmosphere!

cheers,

Bill.

Jeremy's picture
Offline
Last seen: 16 min 30 sec ago
Joined: 04/03/2014 - 22:00
"dissolving" meteors

That's a very interesting meteor video, Bill.

You are beginning to build a nice collection of these enigmatic objects.

Jeremy

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Hi,

Hi,

Thanks. Yes, there is definitely a complete spectrum (no pun intended!) of ablation characteristics.

Reviewing the videos from the other night I also caught a "normal" one on the same system. To show how the ablation differs I made up a comparison video.

It is here:

https://youtu.be/y67mQm70dow

cheers,

Bill.

BillW's picture
Offline
Last seen: 15 hours 18 min ago
Joined: 05/03/2014 - 08:50
Been doing some research....

Been doing some research....

It would appear the "melting" or "dissolving" meteors might be classed as the extreme end of the "dustball" meteors. It is remarkable to consider that given the initial small particle size the meteoroid crumbles to an extremely large collection of even smaller particles. Maybe >mm to micron size before evaporation is complete. What seems a bit of a paradox to me, however, is the textbooks imply that this disintegration speeds up the evaporation due to the smaller particles. That is bigger surface area more rapid ablation. But I think it can be seen that is not what happens in the video. The more robust particle, marked as normal, pops into and out of existance much more rapidly than the dissolving one. Even considering a single tiny particle after initial ablation, the video still gives the impression of a much slower demise. ...AND on top of that the theory also seems to be that the meteor should also be brighter, that too doesn't seem to be the case!

The splitting ones might be an intermediate case of the demise of a dustball. A particular case of unusual fragmentation. The same issues apply about speed and brightness I think and although some meteors are seen to fragment into distinct bits these all appear soft. For reference. Physics of meteor flight through the atmosphere by Opik (heavy duty and I don't understand half of it! ;-) and Meteors comets and meteorites by Hawkins (much easier read and distillation of much of Opiks work). Both quite old texts now but fundamentals are sound. The problems then are still problems now!

I also reviewed a pile of older videos made using shorter focal length lenses and when one really looks closely there are actually quite a few of this type. The longer focal length lenses bring out the effects much more clearly.

So, enigmatic is actually an apt description!

These wonderful little cameras really are re-writing the rules!

cheers,

Bill.