<blockquote>
  <p>What is the <strong>intensity distribution</strong> of visible light over the solar disk?<br>
  What is the <strong>distribution</strong> of the visible <strong>spectrum</strong> over the solar disk</p>
</blockquote>

<p>Hopefully I've answered all the <em>different</em> questions.</p>

<p>The core of the sun is extremely hot (27 million degrees Fahrenheit) compared to the surface (10,000 degrees Fahrenheit) and the atmosphere (36,000 to 2 million degrees Fahrenheit). Source: JPL NASA - "<a href="https://www.jpl.nasa.gov/nmp/st5/SCIENCE/sun.html" rel="nofollow noreferrer">The Sun's Layers and Temperatures</a>". To our eye the sun generally appears to have a single color and brightness due to dynamic range and color mixing.</p>

<p>The <a href="https://en.wikipedia.org/wiki/Air_mass_(solar_energy)#Cases" rel="nofollow noreferrer">AM0 spectrum</a> and intensity <a href="https://commons.m.wikimedia.org/wiki/File:Solar_AM0_spectrum_with_visible_spectrum_background_(en).png" rel="nofollow noreferrer">looks like this</a>:</p>

<p><a href="https://i.sstatic.net/z0h3q.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/z0h3q.png" alt="SM0 Spectrum"></a></p>

<p>Each element emits a different multitude of wavelengths. The distribution across the surface, and out into the atmosphere, varies.</p>

<p>For example here is a <a href="https://www.nasa.gov/mission_pages/sunearth/news/light-wavelengths.html" rel="nofollow noreferrer">set of images taken at different wavelengths</a>:</p>

<p><a href="https://i.sstatic.net/tnyHo.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/tnyHo.jpg" alt="Filtered Sunlight"></a></p>

<p>That answers your <a href="https://astronomy.stackexchange.com/questions/33342/what-is-the-intensity-distribution-of-visible-light-over-the-solar-disk#comment62999_33342">question in this comment</a>:</p>

<blockquote>
  <p>"Ah thank you, that is exactly what I was looking for. But how do <a href="https://scied.ucar.edu/sites/default/files/images/large_image_for_image_content/sun_uv_visible_compare_3feb2002_soho_820x400.jpg" rel="nofollow noreferrer">images like these</a> get produced? Are they adjusting the brightness to be equal througout the image before releasing it? – Jhonny007".</p>
</blockquote>

<p>Images like those are produced by placing filters over the imaging sensor.</p>

<p>Limb darkening is caused by the different temperatures of the different layers. The center of the disk appears bumpy due to <a href="https://en.wikipedia.org/wiki/Granule_(solar_physics)" rel="nofollow noreferrer">granules</a>. Using a greater dynamic range it looks like this:</p>

<p><a href="https://i.sstatic.net/HzhtP.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/HzhtP.jpg" alt="Sun (additive timelapse)"></a></p>

<p><sub><a href="https://www.nasa.gov/mission_pages/sdo/news/first-light-3rd.html" rel="nofollow noreferrer">This image</a> is a composite of 25 separate images spanning the period of April 16, 2012, to April 15, 2013. It uses the SDO AIA wavelength of 171 angstroms and reveals the zones on the sun where active regions are most common during this part of the solar cycle.</sub></p>

<p>A <a href="https://apod.nasa.gov/apod/ap051106.html" rel="nofollow noreferrer">closeup of a sunspot</a> (a colder region, thus darker) looks like this:</p>

<p><a href="https://i.sstatic.net/QDeEw.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/QDeEw.jpg" alt="Sunspot closeup"></a></p>

<p>The website Schurs Solar Imaging, and webpage: "<a href="http://www.schursastrophotography.com/solar/solar-whitelight.html" rel="nofollow noreferrer">Image Gallery of Solar Phenomenon - White Light Features</a>" has a great set of photos, and one clearly showing limb darkening.</p>

<p>Adjusting the contrast of an image from the University of Virginia's webpage: "<a href="http://faculty.virginia.edu/ASTR1230/LECTURES/LECTURE6/lecture6B-s13.html" rel="nofollow noreferrer">ASTR 1230 (Majewski) Lecture Notes</a>" creates an image that shows limb darkening.</p>

<p><a href="https://i.sstatic.net/zYr2O.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/zYr2O.png" alt="Limb Darkening"></a></p>

CC BY-SA 4.0
2019-09-13T03:39:56.460Z
2019-09-13T03:39:56.460Z
Rob
<p>What is the distribution of the visible spectrum over the solar disk?</p>

<p>Images of the Sun using the visible spectrum suggest that the light emmitted from the edge is almost equal to the light emmited from the center of the solar disk.</p>

<p>Is this correct and is there a scientific source that proves that? I was not able to find something citable.</p>

CC BY-SA 4.0
2019-09-12T14:16:47.337Z
Are you asking about [limb darkening](https://en.m.wikipedia.org/wiki/Limb_darkening) ?
astrosnapper
CC BY-SA 4.0
2019-09-12T14:22:52.997Z
Ah thank you, that is exactly what I was looking for. But how do images like [these](https://scied.ucar.edu/sites/default/files/images/large_image_for_image_content/sun_uv_visible_compare_3feb2002_soho_820x400.jpg) get produced? Are they adjusting the brightness to be equal througout the image before releasing it?
Jhonny007
CC BY-SA 4.0
2019-09-12T15:41:36.973Z
@Jhonny007 also see [Is the Sun slightly blue in the center? - Wavelength-dependent limb darkening of the Sun](https://astronomy.stackexchange.com/q/14952/7982) as well as answers to [Need help simulating solar limb darkening](https://space.stackexchange.com/q/16622/12102) for some math. It's perfectly fine to write an answer to your own question if you find what you need.
uhoh
<the-sun><light><visible-light>
What is the intensity distribution of visible light over the solar disk?
Jhonny007
# What is the intensity distribution of visible light over the solar disk?

(Asked by: username_0 on 2019-09-12)

What is the distribution of the visible spectrum over the solar disk?

Images of the Sun using the visible spectrum suggest that the light emmitted from the edge is almost equal to the light emmited from the center of the solar disk.

Is this correct and is there a scientific source that proves that? I was not able to find something citable.

**Tags:** the-sun, light, visible-light

> **Comments:**
> **username_1**: Are you asking about [limb darkening](https://en.m.wikipedia.org/wiki/Limb_darkening) ?  
> **username_0**: Ah thank you, that is exactly what I was looking for. But how do images like [these](https://scied.ucar.edu/sites/default/files/images/large_image_for_image_content/sun_uv_visible_compare_3feb2002_soho_820x400.jpg) get produced? Are they adjusting the brightness to be equal througout the image before releasing it?  
> **username_2**: @username_0 also see [Is the Sun slightly blue in the center? - Wavelength-dependent limb darkening of the Sun](https://astronomy.stackexchange.com/q/14952/7982) as well as answers to [Need help simulating solar limb darkening](https://space.stackexchange.com/q/16622/12102) for some math. It's perfectly fine to write an answer to your own question if you find what you need.  

---

## 1 answers

### Answer by username_3 on 2019-09-13. Score: 4 | Accepted answer

> What is the **intensity distribution** of visible light over the solar disk?  
> What is the **distribution** of the visible **spectrum** over the solar disk

Hopefully I've answered all the *different* questions.

The core of the sun is extremely hot (27 million degrees Fahrenheit) compared to the surface (10,000 degrees Fahrenheit) and the atmosphere (36,000 to 2 million degrees Fahrenheit). Source: JPL NASA - "[The Sun's Layers and Temperatures](https://www.jpl.nasa.gov/nmp/st5/SCIENCE/sun.html)". To our eye the sun generally appears to have a single color and brightness due to dynamic range and color mixing.

The [AM0 spectrum](https://en.wikipedia.org/wiki/Air_mass_(solar_energy)#Cases) and intensity [looks like this](https://commons.m.wikimedia.org/wiki/File:Solar_AM0_spectrum_with_visible_spectrum_background_(en).png):

[![SM0 Spectrum](https://i.sstatic.net/z0h3q.png)](https://i.sstatic.net/z0h3q.png)

Each element emits a different multitude of wavelengths. The distribution across the surface, and out into the atmosphere, varies.

For example here is a [set of images taken at different wavelengths](https://www.nasa.gov/mission_pages/sunearth/news/light-wavelengths.html):

[![Filtered Sunlight](https://i.sstatic.net/tnyHo.jpg)](https://i.sstatic.net/tnyHo.jpg)

That answers your [question in this comment](https://astronomy.stackexchange.com/questions/33342/what-is-the-intensity-distribution-of-visible-light-over-the-solar-disk#comment62999_33342):

> "Ah thank you, that is exactly what I was looking for. But how do [images like these](https://scied.ucar.edu/sites/default/files/images/large_image_for_image_content/sun_uv_visible_compare_3feb2002_soho_820x400.jpg) get produced? Are they adjusting the brightness to be equal througout the image before releasing it? – username_0".

Images like those are produced by placing filters over the imaging sensor.

Limb darkening is caused by the different temperatures of the different layers. The center of the disk appears bumpy due to [granules](https://en.wikipedia.org/wiki/Granule_(solar_physics)). Using a greater dynamic range it looks like this:

[![Sun (additive timelapse)](https://i.sstatic.net/HzhtP.jpg)](https://i.sstatic.net/HzhtP.jpg)

[This image](https://www.nasa.gov/mission_pages/sdo/news/first-light-3rd.html) is a composite of 25 separate images spanning the period of April 16, 2012, to April 15, 2013. It uses the SDO AIA wavelength of 171 angstroms and reveals the zones on the sun where active regions are most common during this part of the solar cycle.

A [closeup of a sunspot](https://apod.nasa.gov/apod/ap051106.html) (a colder region, thus darker) looks like this:

[![Sunspot closeup](https://i.sstatic.net/QDeEw.jpg)](https://i.sstatic.net/QDeEw.jpg)

The website Schurs Solar Imaging, and webpage: "[Image Gallery of Solar Phenomenon - White Light Features](http://www.schursastrophotography.com/solar/solar-whitelight.html)" has a great set of photos, and one clearly showing limb darkening.

Adjusting the contrast of an image from the University of Virginia's webpage: "[ASTR 1230 (Majewski) Lecture Notes](http://faculty.virginia.edu/ASTR1230/LECTURES/LECTURE6/lecture6B-s13.html)" creates an image that shows limb darkening.

[![Limb Darkening](https://i.sstatic.net/zYr2O.png)](https://i.sstatic.net/zYr2O.png)


---

