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Probably a dumb question but about tonights (or last night) lunar eclipse. (fedia.io)

submitted 3 days ago by [email protected] to c/[email protected]

16 comments fedilink hide all child comments

If its a total lunar eclipse why does one edge remains brighter than the rest?

I have been googling for an answer for a while and cant find it. Even pictures of previous total lunar eclipses are the same. Is it because that side remain closer to the edge of the umbra? Or is it caused by how light behaves; Or because the surface of the moon is more reflective on that part.

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[–] Kichae 4 points 3 days ago (1 children)

For the same reason the moon is red and not black: The earth's atmosphere is scattering and bending sunlight. Red light scatters the least, and ends up with the smoothest distribution once it's past by the planet, while bluer light scatters more frequently, and will be more effectively blocked.

Not that "more effectively" is not the same as "totally". This leaves the outer regions of the umbra receiving more light -- and less reddened light -- than the centre of the umbra.

[–] [email protected] 1 points 2 days ago (1 children)

So like the umbra has a "bright" edge compared to its center?

I think that was my mistake, I was thinking of the transition between the penumbra and umbra had a straigt edge when viewed from earth.

thanks

[–] Kichae 3 points 2 days ago (1 children)

Yes, but it's not just brighter near the outer edges, it's whiter, thanks to the inclusion of more blue light, and that less ruddy colour does a lot to affect how we see the gradation from light to dark.

They are harder to find than they should be, but there are pictures of the Earth occulting hte sun out there, and you can see how the Earth's atmosphere is aglow with scattered sunlight. There's more light closer to where the sun is than where isn't. The Blue Ghost lander pictures of the eclipse are probably the most accessible right now:

The earth eclipsing the sun, as seen from the surface of the moon.

The bright ring around the Earth in ths image is sunlight streaming through the Earth's atmosphere. See how blue it looks? And how it gets brighter closer to the sun?

That's why.

[–] [email protected] 2 points 2 days ago

Got it, thats very interesting. I already understood the redness of the shadow but had no idea how much more complex it is and that picture of earth eclipsing the sun makes it way more clearer.

Thank you very much, I would upvote you 10 times if I could.