APOD: The Sun's Spectrum with its Missing... (2018 Sep 26)

[APOD Robot]

The Sun's Spectrum with its Missing Colors

Explanation: It is still not known why the Sun's light is missing some colors. Here are all the visible colors of the Sun, produced by passing the Sun's light through a prism-like device. The spectrum was created at the McMath-Pierce Solar Observatory and shows, first off, that although our white-appearing Sun emits light of nearly every color, it does indeed appear brightest in yellow-green light. The dark patches in the above spectrum arise from gas at or above the Sun's surface absorbing sunlight emitted below. Since different types of gas absorb different colors of light, it is possible to determine what gasses compose the Sun. Helium, for example, was first discovered in 1870 on a solar spectrum and only later found here on Earth. Today, the majority of spectral absorption lines have been identified - but not all.

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[heehaw]

https://en.wikipedia.org/wiki/Joseph_von_Fraunhofer Tells us what a miracle life can be!

[Ann]

https://en.wikipedia.org/wiki/Joseph_von_Fraunhofer Tells us what a miracle life can be!

It was touching to read about Joseph von Fraunhofer, the Mozart of the spectral lines.

Tom Lehrer said about Mozart, "When Mozart was my age, he had been dead for two years". Well, when Fraunhofer was my age, he had been dead for 24 years.

Mozart and Fraunhofer died young, but their important contributions expanded the minds of people all over the world.

Ann

[E Fish]

Why is it that identifying all the spectral absorption lines is difficult? I had assumed that they could be fairly easily identified (by those with that kind of training which I obviously do not have), given the nature of spectral emission and absorption. I'll be introducing a class to the concept of stellar spectra and it might be fun to bring this up.

[Chris Peterson]

Why is it that identifying all the spectral absorption lines is difficult? I had assumed that they could be fairly easily identified (by those with that kind of training which I obviously do not have), given the nature of spectral emission and absorption. I'll be introducing a class to the concept of stellar spectra and it might be fun to bring this up.

I imagine one problem is that with the high degree of thermal and Doppler broadening, there is some ambiguity in even determining the exact wavelength of the lines, or in separating close doublets.

[neufer]

Why is it that identifying all the spectral absorption lines is difficult? I had assumed that they could be fairly easily identified (by those with that kind of training which I obviously do not have), given the nature of spectral emission and absorption. I'll be introducing a class to the concept of stellar spectra and it might be fun to bring this up.

My main task at NOAA was to calculate the outgoing infrared absorption line spectrum for different atmospheric temperature distributions in order that different atmospheric temperature distributions could be identified from the IR spectrum observed from polar orbiting satellites. I always assumed LTE: Local Thermodynamic Equilibrium with minimal "line mixing" resonant interaction between adjacent spectral lines. Both of these assumptions were approximations and the calculations often had to be fudged at the end.

While I knew the frequency and strength of all the lines it was almost impossible to precisely determine the spectra.

Solar atmospheres are far more complicated and variable that Earth's atmosphere.

[Ann]

Why is it that identifying all the spectral absorption lines is difficult? I had assumed that they could be fairly easily identified (by those with that kind of training which I obviously do not have), given the nature of spectral emission and absorption. I'll be introducing a class to the concept of stellar spectra and it might be fun to bring this up.

My main task at NOAA was to calculate the outgoing infrared absorption line spectrum for different atmospheric temperature distributions in order that different atmospheric temperature distributions could be identified from the IR spectrum observed from polar orbiting satellites. I always assumed LTE: Local Thermodynamic Equilibrium with minimal "line mixing" resonant interaction between adjacent spectral lines. Both of these assumptions were approximations and the calculations often had to be fudged at the end.

While I knew the frequency and strength of all the lines it was almost impossible to precisely determine the spectra.

Solar atmospheres are far more complicated and variable that Earth's atmosphere.

I'm impressed, Art. Of course, it makes sense that you have worked as a scientist. Just like other people here - heehaw, maybe?

Ann

[E Fish]

This is really fascinating. It makes perfect sense, but I'd never thought about it before. Thanks for the input, guys. I'm definitely going to read up on this more.

[MarkBour]

This diagram makes it appear that as you get to the shorter wavelengths, there are more and more absorption lines in our sun's spectrum. I wonder why that is ... I suppose it has some quantum-mechanical explanation regarding the number of possible electron-state transitions (?)

[Boomer12k]

What do they mean by "Missing Colors"... do they mean where the absorption lines are??? It is not like "Red" is missing... and when you look at a rainbow...you certainly see all the visible colors... I am not sure what that means....

:---[===] *

[neufer]

This diagram makes it appear that as you get to the shorter wavelengths, there are more and more absorption lines in our sun's spectrum. I wonder why that is ... I suppose it has some quantum-mechanical explanation regarding the number of possible electron-state transitions (?)

There are an infinite number of hydrogen Balmer lines which densely cluster as one approaches the shorter wavelength UV Balmer break of 364.6nm. Throw a bunch of other gas infinite line series on top and that is what one should expect.