APOD: The Deep Lagoon (2023 Sep 28)

[APOD Robot]

The Deep Lagoon

Explanation: Ridges of glowing interstellar gas and dark dust clouds inhabit the turbulent, cosmic depths of the Lagoon Nebula. Also known as M8, The bright star forming region is about 5,000 light-years distant. It makes for a popular stop on telescopic tours of the constellation Sagittarius toward the center of our Milky Way Galaxy. Dominated by the telltale red emission of ionized hydrogen atoms recombining with stripped electrons, this deep telescopic view of the Lagoon's central reaches is about 40 light-years across. The bright hourglass shape near the center of the frame is gas ionized and sculpted by energetic radiation and extreme stellar winds from a massive young star.

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[MelvzLuster]

Great & wonderful, still a star-forming dust but afterward a great galaxy will evolve.

[johnnydeep]

Great & wonderful, still a star-forming dust but afterward a great galaxy will evolve.

Well, the Lagoon Nebula is participating in the evolution of the Milky Way galaxy that it is a part of, but it won't cause the creation of another entire galaxy from it. But perhaps I mistook your meaning.

[Sa Ji Tario]

At most a star cluster, added to the one that already exists

[Christian G.]

More like the Deep Purple Lagoon...Why this color?

[johnnydeep]

At most a star cluster, added to the one that already exists

Which I presume you to mean that more stars may form from the dust and gas in the nebula and become part of NGC 6530:

At the heart of the Lagoon Nebula lies a young, massive star cluster known as
NGC 6530. This cluster, formed from the same interstellar material as the
nebula itself, contains hot, luminous stars that radiate intense ultraviolet light.
This radiation ionizes the surrounding hydrogen gas, causing it to emit a
characteristic crimson glow, giving M8 its striking appearance.

[johnnydeep]

More like the Deep Purple Lagoon...Why this color?

Good question, considering that just a little further out (seen in the full image at https://astrodrudis.com/messier-8-another-view/) the dust is much redder:

Click to view full size image

[orin stepanek]

I took one look and saw a clown sticking his tongue out!

[johnnydeep]

M8-Mos-SL10-DCPrgb-st-154-cC-cr1024.jpg
I took one look and saw a clown sticking his tongue out!

Well, now that you mention it, it kind of looks like the head of a Big Horn Sheep:

Click to view full size image

[Ann]

More like the Deep Purple Lagoon...Why this color?

Good question, considering that just a little further out (seen in the full image at https://astrodrudis.com/messier-8-another-view/) the dust is much redder:

Click to view full size image

Indeed, good question. But if you go to this page, you'll see that the data for this image was acquired through 23 hours 20 minutes exposure through a red Ha filter, 32 hours 40 minutes through a greenish-cyan OIII filter, 24 hours through a red SII filter, and 9 hours 15 minutes through RGB filters.

Do note that the longest exposure was through the cyan-green OIII filter. It seems certain that the OIII filter image was mapped as blue. It is possible that both the Ha filter image and the SII filer image were mapped as red (well, these wavelengths are intrinsically red, of course).

If there is a lot of OIII in the center of the Lagoon Nebula, and certainly a lot of Ha and maybe SII as well, then the combination of a "blue-mapped" OIII image and red Ha and SII images may indeed result in a purple-looking center of the Lagoon Nebula.

Ann

[Christian G.]

More like the Deep Purple Lagoon...Why this color?

Good question, considering that just a little further out (seen in the full image at https://astrodrudis.com/messier-8-another-view/) the dust is much redder:

Click to view full size image

Indeed, good question. But if you go to this page, you'll see that the data for this image was acquired through 23 hours 20 minutes exposure through a red Ha filter, 32 hours 40 minutes through a greenish-cyan OIII filter, 24 hours through a red SII filter, and 9 hours 15 minutes through RGB filters.

Do note that the longest exposure was through the cyan-green OIII filter. It seems certain that the OIII filter image was mapped as blue. It is possible that both the Ha filter image and the SII filer image were mapped as red (well, these wavelengths are intrinsically red, of course).

If there is a lot of OIII in the center of the Lagoon Nebula, and certainly a lot of Ha and maybe SII as well, then the combination of a "blue-mapped" OIII image and red Ha and SII images may indeed result in a purple-looking center of the Lagoon Nebula.

Ann

Thanks for your analysis!

[Chris Peterson]

More like the Deep Purple Lagoon...Why this color?

Good question, considering that just a little further out (seen in the full image at https://astrodrudis.com/messier-8-another-view/) the dust is much redder:

Click to view full size image

Indeed, good question. But if you go to this page, you'll see that the data for this image was acquired through 23 hours 20 minutes exposure through a red Ha filter, 32 hours 40 minutes through a greenish-cyan OIII filter, 24 hours through a red SII filter, and 9 hours 15 minutes through RGB filters.

Do note that the longest exposure was through the cyan-green OIII filter. It seems certain that the OIII filter image was mapped as blue. It is possible that both the Ha filter image and the SII filer image were mapped as red (well, these wavelengths are intrinsically red, of course).

If there is a lot of OIII in the center of the Lagoon Nebula, and certainly a lot of Ha and maybe SII as well, then the combination of a "blue-mapped" OIII image and red Ha and SII images may indeed result in a purple-looking center of the Lagoon Nebula.

Ann

As a matter of how images are typically processed these days: the length of exposure doesn't matter, except to the extent that it defines the level of noise. Different filter channels are mapped to RGB outputs, either directly or in some combination (e.g. [O III] is often distributed into both the green and blue channels). And the values in each channel are normalized and weighted, often in complex ways. Exposing any one channel more or less doesn't mean that the final image will present that channel any brighter or dimmer. Even with simple RGB source images there's a huge range of possible color representations in the final image; throw in some narrowband data and it gets even more variable.

The bottom line on color comes down to one dominant force: what looks good to the image processor.

[orin stepanek]

M8-Mos-SL10-DCPrgb-st-154-cC-cr1024.jpg
I took one look and saw a clown sticking his tongue out!

Well, now that you mention it, it kind of looks like the head of a Big Horn Sheep:

Click to view full size image

That is a beautiful animal Johnny!

[Whiskybreath]

I see pairs of small black dots spread throughout the picture. Are these artefacts of the photographic process?

[Chris Peterson]

I see pairs of small black dots spread throughout the picture. Are these artefacts of the photographic process?

Yes.

[johnnydeep]

I see pairs of small black dots spread throughout the picture. Are these artefacts of the photographic process?

Well I’ll be damned. I thought you must be imagining things, but upon zooming in, those pairs of black dots are clearly visible. They are no doubt artifacts of the imaging or processing, but we’ll need an expert to comment further.