What Causes Distinct Absorption Bands in the Sun's Spectrum During Sunset?

In summary, the person sees bands in the yellow / orange region, blue is attenuated, and red is continuous. There may be a region where there are two or three bands of dark, and the entire spectrum is much dimmer.
  • #1
sophiecentaur
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I recently bought a cheap and cheerful hand held spectroscope. Great fun to look at CFL lamps and the modern LEDs. Those LEDs are really good, btw. Also, the 'scope gives a pretty even spread of brightness over the whole visible range. (an equipment check).
I have been looking at the spectrum of the setting Sun on a regular basis. I see distinct absorption bands in the yellow / orange region. Blue is a bit attenuated, perhaps and red is continuous again. I would like to know what the bands are due to. I am looking at the Sun, low over the London conurbation and I suspect it could be something to do with that.
Any ideas?
I must remember to take the scope with me next time I can see a sunset over a clean horizon. Does that justify a short break in Cornwall??
 
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  • #2
sophiecentaur said:
I see distinct absorption bands in the yellow / orange region.

How many bands can you see? I assume they aren't the sodium lines from the Sun itself?
 
  • #3
Drakkith said:
How many bands can you see? I assume they aren't the sodium lines from the Sun itself?
A question worth asking but the clean solar spectrum is line-free in my scope. I would doubt that the scope resolution would be good enough to spot an absorption line, in any case.
I have been looking at absorption bands from common pollutants and there don't seem to be any obvious candidates. There is much more info on IR absorption, which is what most of the google hits contain.
My observations are very qualitative but I would say that there is a region (say 550 nm to 580nm [Edit Correction- to a bit over 600nm]) where there seem to be two or three ragged bands of dark and the whole of the spectrum there is much dimmer. My eyes and the scope behave themselves fine for the rest of the day. (just been outside and checked again).
 
  • #4
sophiecentaur said:
A question worth asking but the clean solar spectrum is line-free in my scope. I would doubt that the scope resolution would be good enough to spot an absorption line, in any case.

To be safe, I'd give your scope a good shake or two to make sure it isn't lying to you. Let it know you mean business and all that.
 
  • #5
It would need to be far too intelligent to know just when to play up and when not to! I reckon what I am seeing is genuine but it doesn't seem to fit anything I have read about so far. Perhaps there is a cloud of BS over London?
 
  • #6
Brown spectrum( from an M&M coating) matches your description. I think you are definitely on to something. Try your spectroscope over Parliament ! If it matches bilirubin (brown pigment in feces) spectrum you have proof positive.

http://www.trinity.edu/fwalmsle/MandMPictures/BrownSolutionSpectrum.bmp
 

Related to What Causes Distinct Absorption Bands in the Sun's Spectrum During Sunset?

1. What is the atmospheric absorption effect?

The atmospheric absorption effect refers to the process by which gases in the Earth's atmosphere absorb and trap heat from the sun, preventing it from escaping into space. This is a natural phenomenon and is essential for maintaining a livable temperature on Earth.

2. How does the atmospheric absorption effect impact climate change?

The atmospheric absorption effect plays a significant role in climate change. As greenhouse gases such as carbon dioxide and methane become more concentrated in the atmosphere, they trap more heat and contribute to the warming of the planet. This can lead to changes in weather patterns, sea level rise, and other environmental impacts.

3. Which gases contribute to the atmospheric absorption effect?

The most significant contributors to the atmospheric absorption effect are water vapor, carbon dioxide, methane, and ozone. These gases are naturally present in the atmosphere, but human activities such as burning fossil fuels and deforestation have increased their levels, leading to enhanced greenhouse effect and climate change.

4. Is the atmospheric absorption effect reversible?

While the atmospheric absorption effect is a natural process, human activities have significantly intensified it. To reverse its effects, we need to reduce our greenhouse gas emissions and take steps to mitigate climate change. This could include transitioning to renewable energy sources, implementing sustainable land management practices, and promoting conservation efforts.

5. How do scientists study the atmospheric absorption effect?

Scientists study the atmospheric absorption effect through various methods, including satellite observations, ground-based measurements, and computer simulations. These techniques allow them to track changes in greenhouse gas levels, measure the amount of heat trapped in the atmosphere, and predict future climate scenarios. Ongoing research and advancements in technology help improve our understanding of this complex phenomenon.

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