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

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3389
Joined: Fri Dec 04, 2009 3:27 am

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

Post by APOD Robot » Wed Sep 26, 2018 4:05 am

Image 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.

<< Previous APOD This Day in APOD Next APOD >>

heehaw

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

Post by heehaw » Wed Sep 26, 2018 8:56 am

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

User avatar
Ann
4725 Å
Posts: 9167
Joined: Sat May 29, 2010 5:33 am

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

Post by Ann » Wed Sep 26, 2018 12:10 pm

heehaw wrote:
Wed Sep 26, 2018 8:56 am
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
Color Commentator

E Fish
Ensign
Posts: 36
Joined: Thu Mar 09, 2017 2:29 pm

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

Post by E Fish » Wed Sep 26, 2018 1:08 pm

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.

User avatar
Chris Peterson
Abominable Snowman
Posts: 14071
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

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

Post by Chris Peterson » Wed Sep 26, 2018 1:56 pm

E Fish wrote:
Wed Sep 26, 2018 1:08 pm
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.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15507
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

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

Post by neufer » Wed Sep 26, 2018 2:29 pm

E Fish wrote:
Wed Sep 26, 2018 1:08 pm

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.
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 9167
Joined: Sat May 29, 2010 5:33 am

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

Post by Ann » Wed Sep 26, 2018 4:27 pm

neufer wrote:
Wed Sep 26, 2018 2:29 pm
E Fish wrote:
Wed Sep 26, 2018 1:08 pm

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
Color Commentator

E Fish
Ensign
Posts: 36
Joined: Thu Mar 09, 2017 2:29 pm

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

Post by E Fish » Wed Sep 26, 2018 5:55 pm

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.

User avatar
MarkBour
Subtle Signal
Posts: 783
Joined: Mon Aug 26, 2013 2:44 pm
Location: Illinois, USA

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

Post by MarkBour » Wed Sep 26, 2018 8:04 pm

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 (?)
Mark Goldfain

Boomer12k
:---[===] *
Posts: 2369
Joined: Sun Apr 22, 2007 12:07 am

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

Post by Boomer12k » Thu Sep 27, 2018 1:28 am

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....

:---[===] *

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15507
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

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

Post by neufer » Thu Sep 27, 2018 3:16 am

MarkBour wrote:
Wed Sep 26, 2018 8:04 pm

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.
Art Neuendorffer