APOD: The Belt of Venus over Mount Everest (2023 Jun 26)

[APOD Robot]

The Belt of Venus over Mount Everest

Explanation: You've surely seen it, but you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly dark and off-color. Called the Belt of Venus, this transitional band between the dark eclipsed sky and the bright day sky can be seen most prominently in the direction opposite the Sun. Straight above, blue sky is normal sunlight reflecting off the atmosphere, while near the horizon the clear sky can appear more orange or red. In the Belt of Venus, the atmosphere reflects more light from the setting (or rising) Sun and so appears more red. Featured here, the Belt of Venus was photographed over several Himalayan mountains including, second from the right, Mount Everest, the tallest mountain on Earth. Although usually not mentioned, the belt is frequently caught by accident in other photographs.

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[Ann]

Let's try to make head or tails of the colors of today's APOD, shall we?

The Belt of Venus over Mount Everest. Image Credit & Copyright: Soumyadeep Mukherjee

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Let's begin with the Earth's rising (or setting) shadow during sunset (or sunrise). Well, shadows in clear weather on the Earth tend to be blue, right?

Blue shadows and yellowish sunlight during twilight. Credit: Anna Polyakova

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Shadows on white snow are blue, because they are lit up by the blue sky only. During twilight, when sunlight becomes increasingly reddened - because more and more shortwave light is filtered away, and the light that reaches us directly from the Sun is more and more deeply yellow-orange, or even red - shadows and sunlight on the ground can create an obvious blue/yellow effect.


You may have seen this sort of cloudless sunset:

A beautiful cloudless sunset. Credit: r/SanDiego_Photography by SD_TMI

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I wanted to show you this sort of sunset because the sky color deepens to a clear deep red at the horizon. Not all sunsets are like this. Many are just yellowish.

The twilight sky over San Diego is quite dark blue, but the horizon is vividly yellow and red. The color of the Belt of Venus is much paler and more diluted, but the general color scheme is the same. Yellowish sky is followed by pink (not red) sky. And then it is all interrupted by the rising (or setting) blue shadow of the Earth.

I have question. Is that billowing gray stuff seen in the middle of the APOD actually fog?

Ann

[VictorBorun]

Let's try to make head or tails of the colors of today's APOD, shall we?

The Belt of Venus over Mount Everest. Image Credit & Copyright: Soumyadeep Mukherjee

---

Let's begin with the Earth's rising (or setting) shadow during sunset (or sunrise). Well, shadows in clear weather on the Earth tend to be blue, right?

Blue shadows and yellowish sunlight during twilight. Credit: Anna Polyakova

---

Shadows on white snow are blue, because they are lit up by the blue sky only. During twilight, when sunlight becomes increasingly reddened - because more and more shortwave light is filtered away, and the light that reaches us directly from the Sun is more and more deeply yellow-orange, or even red - shadows and sunlight on the ground can create an obvious blue/yellow effect.


You may have seen this sort of cloudless sunset:

A beautiful cloudless sunset. Credit: r/SanDiego_Photography by SD_TMI

---

I wanted to show you this sort of sunset because the sky color deepens to a clear deep red at the horizon. Not all sunsets are like this. Many are just yellowish.

The twilight sky over San Diego is quite dark blue, but the horizon is vividly yellow and red. The color of the Belt of Venus is much paler and more diluted, but the general color scheme is the same. Yellowish sky is followed by pink (not red) sky. And then it is all interrupted by the rising (or setting) blue shadow of the Earth.

I have question. Is that billowing gray stuff seen in the middle of the APOD actually fog?

Ann

They seem to say that this APOD looks in the direction opposite to low Sun's disk.

Thinking about the colours of the sky, I try to have 2 things in mind:

1) from the centre of the disk of Sun there must be rings of red, scarlet, orangish, slightly yellow, grey, slightly cyan, bluish, indigo, violet, gaining in area and losing in brightness, summing up to total illumination to which we adapt as to current white

2) those rings are far from being concentric circles' rings. Each ring gets wider where it passes near horizon and narrower where it passes high. That explains why yellow zone is narrow above the San Diego sunset and wide at horizon

But what is the Belt of Venus, I am at loss

[Guest]

So why do they say Everest is the highest peak? It doesn’t look that way. Oh, they must say it depends on where the “mountain” begins.

[Chris Peterson]

So why do they say Everest is the highest peak? It doesn’t look that way. Oh, they must say it depends on where the “mountain” begins.

It is not based on where the base of the mountain is. Everest is the peak that is highest above mean sea level. You can't look at a range of mountains and reliably say which peak is highest based just on appearance. A closer mountain will appear relatively higher than a more distant one.

[De58te]

So why do they say Everest is the highest peak? It doesn’t look that way. Oh, they must say it depends on where the “mountain” begins.

This is a photographic illusion. Although Everest and Lhotse are adjacent, Makalu is actually 19 kilometers away from Everest. Here Makalu happens to be closer to the camera viewpoint so looks slightly taller.

[fkingery]

Beautiful photo of the Himalaya range. I spent a couple of months there many years ago mapping the geology in view of the then evolving theory of "Mountain Building and The New Global Tectonics."
One comment: in the photo, I believe Lhotse and Everest are mislabeled. Should be the other way around.

[epalmer]

The red and blue colors of the sky do not involve reflection at all, but rather Rayleigh scattering by air molecules. Light at the blue end of the spectrum is scattered more efficiently, dropping off as the fourth power of the wavelength toward the red. This scattering of blue out of the sunlight leaves the "red-heavy" portion of the spectrum to be seen at sunset after the light has made the long trip through the atmosphere at low elevations.

[orin stepanek]

Wow; A lot of great photos in today's APOD

Kitty and doggy playing!

[Ann]

Click to view full size image

Wow; A lot of great photos in today's APOD

Orin, that's a great image! I couldn't find it in the links of today's caption. Where did you find it?

Anyway, Victor, I very much recommend the image posted by Orin, because it does a great job of explaining the Belt of Venus! Or at least I think so.

Don't miss the Earth's shadow on the Moon!

Ann

[bystander]

Click to view full size image

Wow; A lot of great photos in today's APOD

Orin, that's a great image! I couldn't find it in the links of today's caption. Where did you find it?

... the belt is frequently caught by accident in other photographs.

APOD: Shadows of Earth (2023 May 09)

[Ann]

Click to view full size image

Wow; A lot of great photos in today's APOD

Orin, that's a great image! I couldn't find it in the links of today's caption. Where did you find it?

... the belt is frequently caught by accident in other photographs.

APOD: Shadows of Earth (2023 May 09)

Thanks, bystander. I missed it.

Ann

[VictorBorun]

Click to view full size image

Wow; A lot of great photos in today's APOD

Orin, that's a great image! I couldn't find it in the links of today's caption. Where did you find it?

Anyway, Victor, I very much recommend the image posted by Orin, because it does a great job of explaining the Belt of Venus! Or at least I think so.

Don't miss the Earth's shadow on the Moon!

Ann

I think the full moon (and a partial eclipse) is a feature of the direction opposite to the low sun disk, the same direction as in the APOD discussed here.
So I just stay my ground and illustrate it with colour picker from San Diego sunset you showed above

...

Click to view full size image 1 or image 2

[orin stepanek]

Click to view full size image

Wow; A lot of great photos in today's APOD

Orin, that's a great image! I couldn't find it in the links of today's caption. Where did you find it?

Anyway, Victor, I very much recommend the image posted by Orin, because it does a great job of explaining the Belt of Venus! Or at least I think so.

Don't miss the Earth's shadow on the Moon!

Ann

Thanks Ann; bystander got it for me!
Thanks bystander!