Mercury sodium tail

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KMH
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Mercury sodium tail

Post by KMH »

You may have read about the recent visibility of Mercury's sodium tail. A number of elements are sputtered off the surface of Mercury by the combination of solar wind and micrometeorites, forming a very low density (non-collisional) atmosphere of sorts. Some of this material is blown away from Mercury by radiation pressure, similar to what happens with a comet. One of the primary components is atomic sodium, which exhibits very strong resonant scattering at 589 nm. However, the sun has a strong Fraunhofer absorption feature at 589 nm due to sodium in the outer atmosphere, so much of the time the Mercury's sodium tail is not very bright. But +/- about 16 days from perihelion Mercury has it's maximum radial velocity with respect to the sun (its orbit is highly eccentric). The resulting Doppler shift increases the wavelength of the photons necessary for sodium scattering to the wings of the absorption feature, so that the intensity of (Doppler shifted) 589 nm radiation at Mercury increases by about 10x relative to perihelion.
We saw some examples of amateur imaging of the tail using narrow-band filters and decided to give it a try - with success! Still working on processing but here is an example from 5/12/21.
80 mm f/6 refractor
Canon 6D DSLR
Edmund optics 589 nm filter with 10 nm bandpass.
Stacked five 30 second exposures.
There is significant vignetting because the filter is only 1" diameter. Also, it is not an image quality filter, which doesn't help! But we were excited to see anything.
NOTE - the tail was predicted in the 1980s but not observed until 2001.

Kevin
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Re: Mercury sodium tail

Post by Carbon60 »

Excellent, Kevin. That’s a superb image. I first saw this phenomenon on Spaceweather a few days ago. Fascinating.

Stu.


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Re: Mercury sodium tail

Post by marktownley »

Interesting!


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Re: Mercury sodium tail

Post by JochenM »

Very nice capture of it, Kevin.


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Re: Mercury sodium tail

Post by christian viladrich »

Amazing. Well done !
Thanks for sharing.


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Re: Mercury sodium tail

Post by rsfoto »

WOW :o


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Re: Mercury sodium tail

Post by KMH »

Thanks, all. We learned about this on very short notice and were quite lucky to get some shots around the brightness maximum. Hopefully we can try again before too long, maybe having invested in a higher quality filter or even rigging up an occulting disc of some sort.

Here are a couple of links to interesting papers on the subject. The second one (unfortunately behind a pay wall) also shows images of the moon's sodium tail, and also the torus surrounding Jupiter (generated by Io), both with a 100mm scope. Will have to try Jupiter this coming opposition.

Kevin

https://agupubs.onlinelibrary.wiley.com ... 07GL032337

https://link.springer.com/article/10.10 ... 009-9314-y


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Re: Mercury sodium tail

Post by Ylem »

Very nice capture Kevin 🙂


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Re: Mercury sodium tail

Post by Montana »

Wow!! I am amazed :bow :bow :bow it looks like a comet.

Alexandra


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Re: Mercury sodium tail

Post by p_zetner »

I’ll repeat some of the comments above: WOW!
What a terrific, informative post and a fabulous capture.
I had no idea about this phenomenon.
Thanks for enlightening me.
Cheers.
Peter

MODS: Alexandra and Mark, would this be a better fit in the Spectroscopy forum?


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Re: Mercury sodium tail

Post by KMH »

Thanks again, everyone!
We will definitely try this again, maybe with a better filter. We also will try to image the sodium/sulfur cloud around Jupiter this opposition.

One question maybe someone here can help with. It might be helpful to use an occulting bar. I have seen explanations of how to do this with an eyepiece but not so much for imaging (at least at an amateur level). One of the links above shows a dedicated 1x assembly of two identical lenses with the mask at the focal point in between. This assembly is the first element in the optical train. Does anyone have any other thoughts on this?

Thanks,
Kevin


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Re: Mercury sodium tail

Post by ffellah »

Just saw this: pretty amazing phenomenon and capture !

Franco


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Re: Mercury sodium tail

Post by pedro »

Fantastic Kevin, amazing stuff


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Re: Mercury sodium tail

Post by Montana »

This is indeed a fantastic topic Peter, it is probably relevant in both forums, so I will add a copy into the spectroscopy forum so you can find it both here and there in the future :)

Alexandra


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Re: Mercury sodium tail

Post by thesmiths »

For those with a SHG, I suspect one could image in Na and see this effect quite nicely.


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Re: Mercury sodium tail

Post by PEterW »

The guess was that this is too faint for eyeball onserving? The original image came from a 66mm refractor, one does wonder what some aperture and maybe additional filtering could do?
Peter


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Re: Mercury sodium tail

Post by KMH »

I haven't seen any reports of visual sightings. I did see an image though that was taken without any type of filter. Maybe visual would have been possible with the right equipment???
This was a very favorable occurrence - greatest elongation well-timed with respect to perihelion (Mercury's) and combined with a favorable ecliptic inclination. We might have to wait a couple of years for a repeat.


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