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Hi,
I think this is quite an interesting little spectrum. 0508UT 15/3/15. Not very bright and very few lines visble. However it has exceptionally bright OI emission from the “forbidden” transision at 557.7nm. Looking at any other of my spectra here there is no comparable emission in any of them!
Due to the quantum mechanics involved this is a meta stable state, the O atoms sit excited for 0.74 seconds before emitting the photon. So it only occurs with meteors that are very swift and start to or completely abalate above ~100-110km. Below this the atmosphere quenches the transition through collisional loss.
The usual strong Mg and Na so looks like a stony job but it must have been coming straight at us for a very fast effective impact speed. A fascinating addition to the diagnostic info available.
cheers,
Bill.
Hi,
Thanks, that is very useful to know. The velocity of the meteor appears significantly greater than what was expected for either a daD or Qua.
Cheers,
Bill.
Hi William,
Thanks for the offer, I had to dig out my old manual and notes, and nearly called as I was tearing my hair out a one point but I think I’ve got it sorted out.
Analyser classifys it as a sporadic! (it classes the spectrum as a ” -6 flash”). I don’t know how reliable it ultimately is, only a handful of reference stars.
So, there’s at least the possibility that previous professional work might have been based on erroneous assumptions.
Score one for the amateur 🙂
I suppose the next thing to do is to have a look at the Quadrantids parent body. In a previous post I said “sodium deficiency” but that should have been “sodium defficiency with respect to magnesium” as there is no prior knowledge that the material isn’t just like that! The issue with the gemininds is that the sodium has been some how lost due to its orbit and low perihelion distance.
Of course it could all be a lot of nonsense! 😉
cheers,
Bill.
Hi Alex,
I’ve tried it with the mobile rig but the problem I found is it stronly depends on the lens/grating/sky conditions.
I’m not quite sure why there are differences between what are osetensibly the same set ups but some of the gratings seem to be a lot more transparent than others (across the 600 g/mm ones.) and varies the reference stars, if any, that can be seen. That’s the problem. However, I never thought to try the 300g/mm which shows more stars. I caught “Q1” on that too. I’m not sure how it will handle the “width” of the spectrum though. Can you manually indicate start and end points? Then I could select a single line.
It interesting you mention the Geminids. Although I only got one spectrum from that shower despite vastly more meteors, it showed the expected result. That is a sodium deficiency however with the results here I think it can be safely concluded that the quadrantids (or a subset thereof) are sodium deficient too. That might be in the professional literature but I’ve never heard of it. Need to check.
Cheers,
Bill.
Yep, The operational problems caused by moonlight preclude permenant orientation so Analyser not useable which is a pain in the neck.
The following spectrum was derived from an image taken by the Japanese observer Koji Maeda.
I don’t think there can be any more doubt that these spectra reveal there is a particular composition to some Quadrantids. It’s a whole other ball game to consider what might cause the difference (assuming the first spectrum IS of a Quadrantid).
cheers,
Bill.
This is the composite video of the early part of the meteor (Q1). Does this look like it’s coming from a bit off radiant?
What say ye?
I’ve tried other separate video lines and they mostly have more sodium than magnesium. So the binning can be fooled by the interline gaps on images that are not re-oriented perfectly vertically over the whole spectrum in question.
I’ve seen another image from Japan. It only shows limited lines but if the dispersion is as I think then the magnesium line is much stronger than the sodium line. Just like the other three here. The celestial pidgeons might be getting nervous…
cheers,
Bill.
Hi William,
I genuinely cannot believe what is possible now, even a year ago I never imagined I’d be getting such results. The group in the 2005 paper were using image intensifiers and other bits of technology. Now it’s just straight out of the box!
Alex made the point well, once we finally get some mutual orbital data for a good sample size we’re into new territory.
I’ve had no feedback from the “Lens man” yet but if I get a couple of these fast lenses I’ll have sufficient to kit out all the cameras with a fast lens and decent grating. Computing problems are the next issue to be addressed. Need to have a chat with my IT guru’s.With a couple of teasers last year I’m planning on have two south point cameras this year during the Lyrids. weather permitting. The moons situation is good so that’s the plan.
cheers,
Bill.
Well, well, well…
A rough and ready re-do of a SINGLE frame reveals:
The Magnesium line does indeed squeak up a bit! There’s definitely dodgy dealings going on with the binning but I don’t know if this is enough to swing the issue.
It’s all good fun and I’m off for a cuppa….
In an effort to try and find out more about Quadrantid spectra I did a “google”. One paper appeared a few times. Titled “First Results of Quadrantid Meteor Spectrum” by Shinsuke Abe et al. The paper is here: Lunar and Planetary Science XXXVI (2005), PDF 1536.
The text says they analyzed 4 sets of data (mmm there’s another coincidence…). What is truly spooky is the image shown on the summary page is this (which I cut from the document)
Now I have re-aligned and inverted the grey scale on my own image so that an easier comparison can be made, thus:
They are almost identical!
I will need to re-process Q1 in case there is some binning issue or other geometrical effect I’m missed. If the magnesium lines still comes out weaker than the sodium line then that’s a cosmic cat amongst the celestial pidgeons. If it corrects then bigger meteoroids produce more intense emissions. (Perhaps that’s even common sense.) The differences in spectra may then be a function of the way a given mass ablates.
Proper science guv!
cheers,
Bill.
Hi,
Just another thought. Have we ever been in this situation before? By that I mean has there been any other time when so much detailed data has been available for consideration these sorts of questions can even be asked? Rather than just a numbers game we can now get right down to the orbits and composition of the meteorids.
Bodes well for meteor astronomy I think!
Cheers,
Bill.
Hi Alex,
The radiants are quite close. I’ve had another look at the various videos. I’ve only got the tail of Q1 in the wide field. But I caught it on two of the spectro systems. (a 300 g/mm and a 600g/mm) I’m tempted to say it “looks” a touch faster than the others.
Q1 looks very like the fireball spectrum in the other thread. In Q2, Q3 and Q4 the only really prominent atmospheric line is at 777.4nm, the others from O and N are very weak unlike Q1. Since these are taken to be atmospheric this might suggest a less “energetic” entry as, that is perhaps a lower velocity for the 3.
Maybe its a case of just actually believing what we see. Q1 looks significantly different to Q2, Q3 and Q4 so it probably is. Whether it is indeed a sporadic imposter or a daD, that’s another question!
Oh well if it’s not a Quadrantid, and maybe not even a daD then my tweets were all nonsense (but nothing new there then)
It better be clear next year so I can check!
Cheers,
Bill.
Hi,
I find it remarkable that we can do disect the meteor so thoroughly!
My opening sentence should have been “…as weather AND moonlight permits.” It is a significant problem, the gratings are designed to diffract light afterall. It’s just they do is so well in some un-desired circumstances 😉
Mmm, the daD shower is an interesting option, just goes to show the possibilities.
Yes, I had the same idea regarding the Vg. Is this included in the log files that Capture generates for passing to Orbit? Or is it dervied from multiple stations in Orbit? I am clearly out of touch with the subtleties of multi station work. I’ll check the file tonight as that would clinch it. Do you have any Vg values for the daD?
Utterly fascinating.
Cheers,
Bill.
Hi,
Thanks Alex, That’s the plan. I have one on bearing 130 at ~45 deg as weather permits.
Back to the Quadrantids, I did record several others, all fainter and one through considerable cloud. When processing them I noticed something of (possible) significance.
Consider:
These are the synthetic spectra of 4 Quadrantids.
Q1 is of the first post. Q2, Q3 and Q4 were the fainter ones.
Note: I have made no attepmt to align the lines in this case. They were all captured with the same 300 groove/mm grating. Due to varying angles with respect to the dispersion axis it looks like they have different dispersions (the lines at varying distances from one another) this is a geometric effect caused by the re-orientation process. The physical dispersion is the same in all.
Now, it is apparent that Q2, Q3 and Q4 have the green Magnesium (~518nm) line brighter than the yellow Sodium (~590nm) line. With Q1 it is a bit difficult to tell. This is where the graphs now have to come into play.
So,
The graphs are in the same order. It is clear that Q1 is the only one where the Magnesium line (518nm) is lower than the Sodium line (590nm).
(Worthy of a “Ta Dah!” at this point, perhaps)
So does this mean that Q1 was not a Quadrantid, I’m not sure. (I don’t think anyone would be either) A, presumably, slightly larger meteoroid would experience different heating and stress which could conceivably result in a different emission profile.
However, it could be that Q1 was not a Quadrantid afterall and merely was coincidental on the sky with respect to the radiant.
A Quadran Muralis mystery….cheers,
Bill.
….and growing….
Another nice fireball spectrum.This is getting towards the highest resolution meteor spectrum taken using the WATEC generation of video cameras.
A 600 groove/mm fused silica grating but the meteor was caught in the second order so roughly equivalent of a 1200 groove/mm grating in the first order. The double line at the sodium wavelength is genuine. It can be seen evolving in the video but I haven’t been able to identify what it is (yet) The system resolution, even in the second order, doesn’t have the ability to split the sodium doublet so it’s not that. Another interesting meteor mystery!
Fireball 2014 12 28 : 0450UT
Cheers,
Bill.
Now for a plain old iron meteor….
With the exception of a couple of magnesium lines these are all probably iron lines.
Meteor 2014 04 19 : 235419UT
The family tree is growing….
Hi,
Been working through some more spectra. This one looks really nice in the blue. Mostly Iron (Fe) lines here with some additional weak Magnesium lines in the near UV. Taken on 2014 11 15 : 051157UT but using a 300 groove/mm grating. However this shows the effect of “good” geometry even at relatively low dispertions. Looks like a stony iron sporadic.
Cheers,
Bill.
Hi William,
The size, that is span of wavelength, is just a consequence of what bit of the spectrum was in the field of view.
The actual dispersion is the same. The sporadic fireball was a bullseye. It went across the fov slightly diagonally but dead centre. So the whole range of the (silicon) detector was utilised and a full range spectrum was caught, from the UV cut off of the glass to nearly the edge of the silicon “band gap” at just over 1000nm. Actually that was a remarkably lucky catch!
You have a greater chance of catching the whole spectrum if one uses a lower dispersion grating. But then the resolution drops, it’s all a compromise.
cheers,
Bill.
Hi,
Poor weather washed out the peak night sadly but the night before had 8 1/2 hours clear and the night after about 6 1/4 hours mostly nclear with some cloud and showers.
A decent haul and some nice captures but only one useable Geminid spectum. It shows a very prominent magnesium line (left most large peak) and a lesser sodium line. The other fainter lines are also magnesium and iron.
Cheers,
Bill.
