APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

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APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by APOD Robot » Wed May 25, 2022 4:06 am

Image The Lively Center of the Lagoon Nebula

Explanation: The center of the Lagoon Nebula is a whirlwind of spectacular star formation. Visible near the image center, at least two long funnel-shaped clouds, each roughly half a light-year long, have been formed by extreme stellar winds and intense energetic starlight. A tremendously bright nearby star, Herschel 36, lights the area. Vast walls of dust hide and redden other hot young stars. As energy from these stars pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds which may cause the funnels. This picture, spanning about 10 light years, combines images taken in six colors by the orbiting Hubble Space Telescope. The Lagoon Nebula, also known as M8, lies about 5000 light years distant toward the constellation of the Archer (Sagittarius).

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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by Ann » Wed May 25, 2022 5:14 am

I've always been weirded out by that juxtaposition of flat bright yellow and flat bright cyan in the Hubble image of the center of the Lagoon:

Lagoon Nebula center.png

Hubblesite wrote:

The Hubble view shows off the bubble’s 3D structure. Dust pushed away from the star reveals the glowing oxygen gas (in blue) behind the blown-out cavity. Herschel 36’s brilliant light is illuminating the top of the cavity (in yellow). The reddish hue that dominates part of the region is glowing nitrogen. The dark purple areas represent a mixture of hydrogen, oxygen, and nitrogen.
Yeah, well.

It is an interesting image, to be sure. But I've never quite been able to understand the structures that we are seeing. Herschel 36’s brilliant light is illuminating the top of the cavity (in yellow) - really?

Ann
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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by AVAO » Wed May 25, 2022 5:48 am

APOD Robot wrote: Wed May 25, 2022 4:06 am This picture[/url], spanning about 10 light years, combines images taken in six colors by the orbiting Hubble Space Telescope.
I think it would be better to talk about wavelengths instead of colors here. the stars are "borrowed" from the near infrared and many of them would probably not be visible at all in visible light.

Beaker42

Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by Beaker42 » Wed May 25, 2022 6:18 am

Does anyone have an idea why it appears that the star groups on the left of the image appear to be arrayed in chains of stars? Is this an optical illusion, human visual pattern matching? Or are there really chains of stars (or at least stars arranged in flat planes oriented edge-on towards us) ? I have noticed this effect in other Hubble photos, but it seems quite pronounced in this one.

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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by Ann » Wed May 25, 2022 7:50 am

Beaker42 wrote: Wed May 25, 2022 6:18 am Does anyone have an idea why it appears that the star groups on the left of the image appear to be arrayed in chains of stars? Is this an optical illusion, human visual pattern matching? Or are there really chains of stars (or at least stars arranged in flat planes oriented edge-on towards us) ? I have noticed this effect in other Hubble photos, but it seems quite pronounced in this one.
STScI-01EVT0PK28WGSJV4K5601FJGRH[1].png
Lagoon Nebula in visible light. Credits: NASA, ESA, and STScI.


As you can see, the small red stars that pepper the field in today's APOD are not seen at all in the original NASA image (at left). But as AVAO pointed out, the red stars are probably infrared objects, and the original NASA image shows the center of the Lagoon Nebula in visible light.

As to why the stars appear to be arranged in chains, there are two possibilities. Either it is just a chance configuration of stars at similar or different distances seen in projection. But it might - might, mind you - reflect the tendency of stars to be born from elongated dust lanes.


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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by astrozsarac » Wed May 25, 2022 10:10 am

AVAO wrote: Wed May 25, 2022 5:48 am
APOD Robot wrote: Wed May 25, 2022 4:06 am This picture[/url], spanning about 10 light years, combines images taken in six colors by the orbiting Hubble Space Telescope.
I think it would be better to talk about wavelengths instead of colors here. the stars are "borrowed" from the near infrared and many of them would probably not be visible at all in visible light.
Aren't visible light colors actually wavelets? Color wavelengths that we cannot see do not change the fact that they exist.

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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by Chris Peterson » Wed May 25, 2022 12:45 pm

astrozsarac wrote: Wed May 25, 2022 10:10 am
AVAO wrote: Wed May 25, 2022 5:48 am
APOD Robot wrote: Wed May 25, 2022 4:06 am This picture[/url], spanning about 10 light years, combines images taken in six colors by the orbiting Hubble Space Telescope.
I think it would be better to talk about wavelengths instead of colors here. the stars are "borrowed" from the near infrared and many of them would probably not be visible at all in visible light.
Aren't visible light colors actually wavelets? Color wavelengths that we cannot see do not change the fact that they exist.
Wavelength is a physical property of light. Color is a physiological response or categorization. Filters do not pass "colors" they pass wavelengths of light. That data is then processed in a way that maps it to the primary display channels, which results in our eyes perceiving color. Generally, no light should be referred to using the term "color" when we're considering astronomical images like this. But I agree with AVAO that using the term for wavelengths that we can't even see is a particularly bad idea. (It can be a fine line between simplifying language for a broad audience and dumbing down language. I think this is too far towards the latter.)
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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by orin stepanek » Wed May 25, 2022 12:46 pm

LagoonCenter_HubbleOzsarac_3937.jpg
Lagoon center; sounds like a scary place! :shock: Nice to look at but
sounds like not a nice place to visit :mrgreen:
450px-VST_images_the_Lagoon_Nebula.jpg
Beautiful Lagoon nebula! I always thought of as a very beautiful
nebula! 8-)
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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by johnnydeep » Wed May 25, 2022 2:49 pm

Ann wrote: Wed May 25, 2022 7:50 am
Beaker42 wrote: Wed May 25, 2022 6:18 am Does anyone have an idea why it appears that the star groups on the left of the image appear to be arrayed in chains of stars? Is this an optical illusion, human visual pattern matching? Or are there really chains of stars (or at least stars arranged in flat planes oriented edge-on towards us) ? I have noticed this effect in other Hubble photos, but it seems quite pronounced in this one.
As you can see, the small red stars that pepper the field in today's APOD are not seen at all in the original NASA image (at left). But as AVAO pointed out, the red stars are probably infrared objects, and the original NASA image shows the center of the Lagoon Nebula in visible light.

...
Ann
Per the text, are not all the red stars due to interstellar reddening?
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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by Ann » Wed May 25, 2022 5:42 pm

johnnydeep wrote: Wed May 25, 2022 2:49 pm
Ann wrote: Wed May 25, 2022 7:50 am
Beaker42 wrote: Wed May 25, 2022 6:18 am Does anyone have an idea why it appears that the star groups on the left of the image appear to be arrayed in chains of stars? Is this an optical illusion, human visual pattern matching? Or are there really chains of stars (or at least stars arranged in flat planes oriented edge-on towards us) ? I have noticed this effect in other Hubble photos, but it seems quite pronounced in this one.
As you can see, the small red stars that pepper the field in today's APOD are not seen at all in the original NASA image (at left). But as AVAO pointed out, the red stars are probably infrared objects, and the original NASA image shows the center of the Lagoon Nebula in visible light.

...
Ann
Per the text, are not all the red stars due to interstellar reddening?
Reddening is not constant, but it is variable depending on the amount of dust in front of the stars.

Rho Oph and IC 4603 Thomas Davis.png
Stars Rho Oph and HD 147889 in IC 4603 are reddened by different amounts.
Credit: Thomas V. Davis.

The dust cloud in front of a star field demonstrates the nature of reddening. An interesting example of variable reddening can be found in the Rho Ophiuchi and IC 4603 region. Rho Ophiuchi and HD 147899 belong to the same spectral class, B2, and they are intrinsically probably more or less the same color. We would expect an unreddened star of spectral class B2 to have a B-V index of around -0.2. However, both Rho Oph and HD 147899 are reddened by dust, but they are reddened by different amounts. The B-V index of Rho Oph is +0.23, whereas the B-V index of HD 147899 is +0.76. In the case of Rho Oph, much of its blue light has been scattered in a large reflection nebula, but in the case of HD 147899, the star is hidden behind so much dust the the reflection nebula surrounding it is barely blue.

My point is that I don't expect the stars near the center of the Lagoon Nebula to be reddened by the same amount. But they do, indeed, look about equally red. My guess is that these stars have been detected by one and the same infrared filter, and therefore the huge majority of them appear to be the same shade of red. Most of them would not be visible at optical wavelengths.

Ann
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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by johnnydeep » Wed May 25, 2022 6:53 pm

Ann wrote: Wed May 25, 2022 5:42 pm
johnnydeep wrote: Wed May 25, 2022 2:49 pm
Ann wrote: Wed May 25, 2022 7:50 am

As you can see, the small red stars that pepper the field in today's APOD are not seen at all in the original NASA image (at left). But as AVAO pointed out, the red stars are probably infrared objects, and the original NASA image shows the center of the Lagoon Nebula in visible light.

...
Ann
Per the text, are not all the red stars due to interstellar reddening?
Reddening is not constant, but it is variable depending on the amount of dust in front of the stars.

Rho Oph and IC 4603 Thomas Davis.png
Stars Rho Oph and HD 147889 in IC 4603 are reddened by different amounts.
Credit: Thomas V. Davis.

The dust cloud in front of a star field demonstrates the nature of reddening. An interesting example of variable reddening can be found in the Rho Ophiuchi and IC 4603 region. Rho Ophiuchi and HD 147899 belong to the same spectral class, B2, and they are intrinsically probably more or less the same color. We would expect an unreddened star of spectral class B2 to have a B-V index of around -0.2. However, both Rho Oph and HD 147899 are reddened by dust, but they are reddened by different amounts. The B-V index of Rho Oph is +0.23, whereas the B-V index of HD 147899 is +0.76. In the case of Rho Oph, much of its blue light has been scattered in a large reflection nebula, but in the case of HD 147899, the star is hidden behind so much dust the the reflection nebula surrounding it is barely blue.

My point is that I don't expect the stars near the center of the Lagoon Nebula to be reddened by the same amount. But they do, indeed, look about equally red. My guess is that these stars have been detected by one and the same infrared filter, and therefore the huge majority of them appear to be the same shade of red. Most of them would not be visible at optical wavelengths.

Ann
Ok, got it - thanks.
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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by AVAO » Wed May 25, 2022 7:18 pm

Ann wrote: Wed May 25, 2022 5:42 pm
My point is that I don't expect the stars near the center of the Lagoon Nebula to be reddened by the same amount. But they do, indeed, look about equally red. My guess is that these stars have been detected by one and the same infrared filter, and therefore the huge majority of them appear to be the same shade of red. Most of them would not be visible at optical wavelengths.

Ann
This star-filled image, taken by Hubble in near-infrared wavelengths of light (right side), reveals a very different view of the Lagoon Nebula compared to its visible-light portrait. The observations were taken by Hubble’s Wide Field Camera 3 (WFC3) instrument between February 12 and 18, 2018. Image credit: NASA / ESA / STScI.

Image
https://hubblesite.org/contents/media/i ... Image.html

Today's APOD is probably a combination of these wavelengths. ... and a sixth?

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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by Chris Peterson » Wed May 25, 2022 7:26 pm

AVAO wrote: Wed May 25, 2022 7:18 pm
Ann wrote: Wed May 25, 2022 5:42 pm
My point is that I don't expect the stars near the center of the Lagoon Nebula to be reddened by the same amount. But they do, indeed, look about equally red. My guess is that these stars have been detected by one and the same infrared filter, and therefore the huge majority of them appear to be the same shade of red. Most of them would not be visible at optical wavelengths.

Ann
This star-filled image, taken by Hubble in near-infrared wavelengths of light, reveals a very different view of the Lagoon Nebula compared to its visible-light portrait. The observations were taken by Hubble’s Wide Field Camera 3 (WFC3) instrument between February 12 and 18, 2018. Image credit: NASA / ESA / STScI.

Image
https://hubblesite.org/contents/media/i ... Image.html

Today's APOD is probably a combination of these wavelengths. ... and a sixth?
Red: WFC3/IR F160W
Orange: WFC3/IR F125W
Yellow-Green: WFC3/UVIS F658N
Green-Blue: WFC3/UVIS F656N
Cyan: WFC3/UVIS F547M
Blue: WFC3/UVIS F502N

The mapping, stated this way, is a bit odd and ambiguous, as cyan, yellow, and orange aren't primaries in this image.
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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by markb212 » Thu May 26, 2022 3:42 am

Very interesting discussions of wavelengths in this image and how they're mapped "to the primary display channels ..." (Chris). But does anyone else see a winged creature hovering over that central area?

(Sorry, it's the first thing I noticed 🙄.)

Mark B.

Beaker42

Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by Beaker42 » Thu May 26, 2022 5:17 am

markb212 wrote: Thu May 26, 2022 3:42 am Very interesting discussions of wavelengths in this image and how they're mapped "to the primary display channels ..." (Chris). But does anyone else see a winged creature hovering over that central area?

(Sorry, it's the first thing I noticed 🙄.)

Mark B.
Yes... It was the first thing I saw too! This image immediately came to mind:

Image

:shock:

Oh.. Ann, thanks for answering my 'star-chains' question!

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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by bystander » Thu May 26, 2022 6:14 am

AVAO wrote: Wed May 25, 2022 7:18 pm This star-filled image, taken by Hubble in near-infrared wavelengths of light (right side), reveals a very different view of the Lagoon Nebula compared to its visible-light portrait. The observations were taken by Hubble’s Wide Field Camera 3 (WFC3) instrument between February 12 and 18, 2018. Image credit: NASA / ESA / STScI.

Image
https://hubblesite.org/contents/media/i ... Image.html

Today's APOD is probably a combination of these wavelengths. ... and a sixth?

WFC3/UVIS F547M Luminosity
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Re: APOD: The Lively Center of the Lagoon Nebula (2022 May 25)

Post by AVAO » Thu May 26, 2022 6:23 am

bystander wrote: Thu May 26, 2022 6:14 am
AVAO wrote: Wed May 25, 2022 7:18 pm This star-filled image, taken by Hubble in near-infrared wavelengths of light (right side), reveals a very different view of the Lagoon Nebula compared to its visible-light portrait. The observations were taken by Hubble’s Wide Field Camera 3 (WFC3) instrument between February 12 and 18, 2018. Image credit: NASA / ESA / STScI.

Image
https://hubblesite.org/contents/media/i ... Image.html

Today's APOD is probably a combination of these wavelengths. ... and a sixth?

WFC3/UVIS F547M Luminosity
Thank's Chris and bystander for more detailed informations.