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The molecular universe - short and long wave infrared spectroscopy

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#1 mwr

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Posted 06 October 2019 - 04:48 AM

Molecular absorption bands of polycyclic aromatic hydrocarbons (PAHs) can be observed in infrared spectra of planetary nebula and dust clouds. The "big-11 feauture" at 11 micrometer in the LWIR is very typical for PAHs combined with silicium carbid (SiC). These molecules carry the IR emission features that dominate the spectra of most galactic and extragalactic sources.

 

Is somebody in the CN-community able of doing infrared spectroscopy (or astrophotography) at short (1.4-3 microns) or long (8-15 microns) wavelenght? The atmospheric IR window should allow this. Equipment is obviously very expensive (Allied Vision Goldeye camera with an InGaAs-sensor for SWIR  starts at 11'000,- Euros; for LWIR even special telescopes with gold-plated mirrors are necessary: PlaneWave offers a 12.5 inch Dall-Kirkham for 14'000,- Euros).

 

 

 

 



#2 mwr

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Posted 09 October 2019 - 12:55 PM

As an illustrative example I have attached a typical spectrum of a planetray nebula (taken from: Shaw: Astrochemistry; Wiley; the broad peaks are attributed to PAHs vibration bands):

 

 

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  • PAHs.jpg


#3 philipdehazya

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Posted 09 October 2019 - 04:25 PM

Interesting. What does the detection of PAHs' mean? Important? Another group of molecules? What significance? We want to know!

P.S. Do you mean silicon carbide instead of  silicium carbid (or is that the German for it??)

Thanks-Phil



#4 Organic Astrochemist

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Posted 09 October 2019 - 09:24 PM

Polycyclic aromatic hydrocarbons (PAH) are a fascinating group of molecules in space and on earth (some of which came from space). Thank you for sharing.

But if you expand your definition of a molecule, there are lots of molecules readily observable with inexpensive amateur equipment in the optical and near infrared.
See this very readable review:
https://arxiv.org/pdf/0912.5085.pdf
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#5 mwr

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Posted 10 October 2019 - 01:07 PM

Interesting. What does the detection of PAHs' mean? Important? Another group of molecules? What significance? We want to know!

P.S. Do you mean silicon carbide instead of  silicium carbid (or is that the German for it??)

Thanks-Phil

Phil, of course you are right: I meant silicon carbide (English is not my mother language....)

Polycyclic aromatic hydrocarbons are some of the most ubiquitous organic compounds found in the universe, and have been detected in interplanetary dust particles, the interstellar medium and asteroidal meteorite parent bodies. PAHs may serve as membrane stabilizers for primitive cells on the prebiotic Earth and have special astrobiological significance. So I was wondering if these molecules could be detected in deep sky objects by amateur astronomers who are equipped with specialized equipment like infrared cameras (see my first post on this topic). So far, I haven't found any post on this topic in Cloudy Nights. May be the necessary equipment is yet too expensive.



#6 robin_astro

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Posted 11 October 2019 - 05:53 AM

I do remember seeing perhaps 10-15 years ago an image of Mars taken using a thermal imaging camera in a paper presented at an SAS conference (possibly by Dale Mais, I'm not sure)  but thermal imaging technology has moved on enormously since then so it is perhaps surprising if nobody has tried it since.  One problem though is everything looks bright in the IR even the telescope mirrors.  Also although there are windows in the atmospheric transmission, I see a lot of airglow  in my spectra in the near IR around 1um at least. I am not sure what the atmosphere looks like further into the IR though. 


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#7 robin_astro

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Posted 11 October 2019 - 06:14 AM

I do remember seeing perhaps 10-15 years ago an image of Mars taken using a thermal imaging camera in a paper presented at an SAS conference (possibly by Dale Mais, I'm not sure)  

It was Tom Kaye

SAS conference 2006  proceedings page 151,  downloadable here

http://www.socastros...blications.html

 

Robin


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#8 mwr

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Posted 11 October 2019 - 07:34 AM

Finally I have found a highly interesting presentation on near infrared deep sky observations by Christian Buil. It contains, among others, an image of the star CW Leo - probably one of the first made by an amateur as stated by Christian.

 

http://www.astrosurf...ared/obs_en.htm



#9 robin_astro

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Posted 11 October 2019 - 08:36 AM

Finally I have found a highly interesting presentation on near infrared deep sky observations by Christian Buil. 

This is only at 0.85 microns though, still within the range of CCD/CMOS technology. The observations you mention in the OP are much further into the IR beyond the range of CCD/CMOS.

 

Buil and others have also investigated spectroscopy to the limits of this conventional technology  eg

http://www.astrosurf...ires_ir/obs.htm

 

Cheers

Robin


Edited by robin_astro, 11 October 2019 - 08:50 AM.


#10 robin_astro

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Posted 11 October 2019 - 08:56 AM

But if you expand your definition of a molecule, there are lots of molecules readily observable with inexpensive amateur equipment in the optical and near infrared.
See this very readable review:
https://arxiv.org/pdf/0912.5085.pdf

And you can add comets and the gas planets to that list of course which also have molecular signatures within the range of CCD/CMOS technology. Not in deep sky objects or the interstellar medium by amateurs though that I have been able to find.  I wonder if there are any detectable within say 360-1000nm ?

 

Robin


Edited by robin_astro, 11 October 2019 - 08:57 AM.


#11 robin_astro

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Posted 11 October 2019 - 09:18 AM

See this very readable review:
https://arxiv.org/pdf/0912.5085.pdf

I did not realise that the sunspots in what is a G2v spectral class are cool enough to produce detectable TiO absorption. Interesting !

 

Robin




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