<p>I believe that the answer is mainly the first (directly from stars), although there will certainly be some of each of the others. The diffuseness comes from the fact that there are many more relatively dim stars than rods in the retina of the human eye.  My argument for this is that magnified photographs of most of the Milky Way at least, break down into individiual stars, as seen in this image from astropixels.com</p>

<p><a href="https://i.sstatic.net/JZXZ5.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/JZXZ5.jpg" alt="image of Milky Way from astropixels.xom"></a></p>

CC BY-SA 4.0
2020-05-17T01:39:06.937Z
It's not just the limited number of receptors, the optics of the eye are unable to focus the galaxy well enough to separate the light from the different stars. The diffraction limit means even ideal optics would need to be far larger than the lens of the human eye, and the optics of human eyes are far from ideal.
Christopher James Huff
CC BY-SA 4.0
2020-05-16T10:33:54.620Z
2020-05-16T10:33:54.620Z
Steve Linton
<p>I'm asking here about the <strong><em>diffuse glow</em></strong> seen by the human eye, when looking at the Milky Way.</p>

<p>Where do those visible photons come from exactly?</p>

<ul>
<li>the surface of a star?</li>
<li>starlight bouncing off something (dust or a molecule)?</li>
<li>emitted by gas in the interstellar medium?</li>
<li>all of the above?</li>
</ul>

<milky-way><photons>
Milky Way as seen by the human eye: where exactly do those photons come from?
John
# Milky Way as seen by the human eye: where exactly do those photons come from?

(Asked by: username_0 on 2020-05-15)

I'm asking here about the ***diffuse glow*** seen by the human eye, when looking at the Milky Way.

Where do those visible photons come from exactly?

* the surface of a star?
* starlight bouncing off something (dust or a molecule)?
* emitted by gas in the interstellar medium?
* all of the above?

**Tags:** milky-way, photons


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## 1 answers

### Answer by username_1 on 2020-05-16. Score: 4 | Accepted answer

I believe that the answer is mainly the first (directly from stars), although there will certainly be some of each of the others. The diffuseness comes from the fact that there are many more relatively dim stars than rods in the retina of the human eye. My argument for this is that magnified photographs of most of the Milky Way at least, break down into individiual stars, as seen in this image from astropixels.com

[![image of Milky Way from astropixels.xom](https://i.sstatic.net/JZXZ5.jpg)](https://i.sstatic.net/JZXZ5.jpg)

> **Comments:**
> **username_2**: It's not just the limited number of receptors, the optics of the eye are unable to focus the galaxy well enough to separate the light from the different stars. The diffraction limit means even ideal optics would need to be far larger than the lens of the human eye, and the optics of human eyes are far from ideal.  

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