APOD: The Light, Dark, and Dusty Trifid (2024 Aug 10)

[APOD Robot]

The Light, Dark, and Dusty Trifid

Explanation: Messier 20, popularly known as the Trifid Nebula, lies about 5,000 light-years away toward the nebula rich constellation Sagittarius. A star forming region in the plane of our galaxy, the Trifid does illustrate three different types of astronomical nebulae; red emission nebulae dominated by light from hydrogen atoms, blue reflection nebulae produced by dust reflecting starlight, and dark nebulae where dense dust clouds appear in silhouette. The reddish emission region, roughly separated into three parts by obscuring dust lanes, is what lends the Trifid its popular name. The cosmic cloud complex is over 40 light-years across and would cover the area of a full moon on planet Earth's sky. But the Trifid Nebula is too faint to be seen by the unaided eye. Over 75 hours of image data captured under dark night skies was used to create this stunning telescopic view.

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[JimB]

The second law of thermodynamics says that the entropy of a system is always increasing, and so eventually everything will be in a state of max disorder and "evenly mixed", but looking scenes like the Triffid Nebula (estimated age 300,000 years) it's difficult to imagine that the universe will ever be evenly mixed.

[Christian G.]

Are there new stars actively forming in the Trifid Nebula?
The wiki link sates that "the massive ionizing HD 164492A, an O7.5III star is surrounded by a cluster of approximately 3100 young stars" while the NASA link says that "Star formation is no longer occurring in the immediate vicinity of this group of bright stars because their intense radiation has blown away the gas and dust from which new stars are made", and it's not clear if they mean the group of 3100 young stars mentioned by wiki or rather the former O7 star which other sources claim to be a multiple star system.

[Christian G.]

p.s. and just to add a little more blue to the reflection area of the nebula...

(David Dayag)

[AVAO]

The second law of thermodynamics says that the entropy of a system is always increasing, and so eventually everything will be in a state of max disorder and "evenly mixed", but looking scenes like the Triffid Nebula (estimated age 300,000 years) it's difficult to imagine that the universe will ever be evenly mixed.

...I agree with you. The area around the Trifid Nebula (bottom left Lagoon Nebula) also seems to be quite dynamic in the radio (white) and IR (red/blue) frequency range. But what we see here are only fragments of the last few hundred thousand years. Nothing in astronomical terms...
Cosmic flowers that quickly bloom but also quickly fade again.

Click to view full size image 1 or image 2

Original datra: NASA/ESA Radio (RACS) IR (GLIMPSE) jac berne (flickr)


See also corparison optical/IR (SST): https://viewspace.org/resources/invisib ... fid_nebula

[Chris Peterson]

The second law of thermodynamics says that the entropy of a system is always increasing, and so eventually everything will be in a state of max disorder and "evenly mixed", but looking scenes like the Triffid Nebula (estimated age 300,000 years) it's difficult to imagine that the universe will ever be evenly mixed.

To be fair, that's like putting a drop of food coloring in a glass of water and after one second saying it's difficult to imagine you'll ever see an even mixture...

[AVAO]

Are there new stars actively forming in the Trifid Nebula?
The wiki link sates that "the massive ionizing HD 164492A, an O7.5III star is surrounded by a cluster of approximately 3100 young stars" while the NASA link says that "Star formation is no longer occurring in the immediate vicinity of this group of bright stars because their intense radiation has blown away the gas and dust from which new stars are made", and it's not clear if they mean the group of 3100 young stars mentioned by wiki or rather the former O7 star which other sources claim to be a multiple star system.

Information on Wikipedia is only partially reliable and may be taken out of context. The 3100 young stars refer to the Trifid region and are not spatially defined in the study. Of the 17 star formation regions examined, the Trifid region has the lowest star density with 10 stars per pc−2. I therefore do not think that the two statements contradict each other. However, such comparisons must also take into account the respective distances between the objects under investigation.

[Ann]

The second law of thermodynamics says that the entropy of a system is always increasing, and so eventually everything will be in a state of max disorder and "evenly mixed", but looking scenes like the Triffid Nebula (estimated age 300,000 years) it's difficult to imagine that the universe will ever be evenly mixed.

...I agree with you. The area around the Trifid Nebula (bottom left Lagoon Nebula) also seems to be quite dynamic in the radio (white) and IR (red/blue) frequency range. But what we see here are only fragments of the last few hundred thousand years. Nothing in astronomical terms...
Cosmic flowers that quickly bloom but also quickly fade again.

Click to view full size image 1 or image 2

Original datra: NASA/ESA Radio (RACS) IR (GLIMPSE) jac berne (flickr)


See also corparison optical/IR (SST): https://viewspace.org/resources/invisib ... fid_nebula

Wow, Jac, those are some radio bubbles. Particularly the one at 2 o'clock. I've tried to match the bubble with anything interesting in the visible department and the general location of it, but all I have come up with is an unimpressive nebula, Sharpless 26:

The picture wouldn't open for me, so I posted it as an attachment.

Ann

[Ann]

Are there new stars actively forming in the Trifid Nebula?
The wiki link sates that "the massive ionizing HD 164492A, an O7.5III star is surrounded by a cluster of approximately 3100 young stars" while the NASA link says that "Star formation is no longer occurring in the immediate vicinity of this group of bright stars because their intense radiation has blown away the gas and dust from which new stars are made", and it's not clear if they mean the group of 3100 young stars mentioned by wiki or rather the former O7 star which other sources claim to be a multiple star system.

I believe that new stars are forming here:

Possible star formation in the Trifid Nebula.
Credit: NASA, JPL-Caltech, J. Rho (SSC/Caltech)

Ann

[Ann]

p.s. and just to add a little more blue to the reflection area of the nebula...

Credit: David Dayag

---

Thank you, Christian, you knew what I needed!

Ann

[Ann]

As Christian surmised, I'm not too happy with the non-blue appearance of the blue hue of the reflection nebula part of the APOD.

Let's compare the APOD with a picture that I like very much myself:

The Trifid Nebula. Credit: Image Credit & Copyright: Robert Edelmaier and Gabriele Gegenbauer

---

The Trifid Nebula. Credit: Emmanuel Astronomono

---

As you can see, the colors of Emmanuel Astronomono's picture are much more saturated than the colors of the APOD. For myself, I'm okay with a pale pink hue of the central emission nebula, but I definitely want a bluer version of the reflection nebula than what the APOD offers. To me it barely looks blue at all. Indeed, at first I didn't even realize that I was looking at the Trifid Nebula!

If you go to Robert Edelmaier and Gabriele Gegenbauer's website, you can see that they used not only RGB filters for their image, and not just RGB + Hα filters either, but RGB + Hα + OIII + SII filters. There is no way that you are going to get a good RGB color image from the use of all those filters. If all the filters have been used to detect nebulosity, then we must be dealing with a false color (or, as Chris would say, a mapped color) nebula.

We should note that the reflection nebula in the APOD is definitely larger (and also brighter) than the reflection nebula in Emmanuel Astronomono's image. My guess is that one or more of the narrowband filters have detected nebulosity at a larger distance from the central Trifid than RGB filters typically do. It wouldn't surprise me at all if some of the outermost nebulosity in the APOD is faint red SII.

We are definitely seeing much more red Hα than we usually do in the vicinity of the Trifid, at upper right and lower right.

In any case, the visually blue reflection nebula has been mixed with colors detected by narrowband filters, and the image has been processed so that the reflection nebula is a pale shade of gray, even beige.

An interesting aspect of the APOD is that the pink emission nebula looks smooth, whereas the "blue" reflection nebula looks extremely tousled, like a poor cat's or dog's wildly unkempt fur. Of course, the pink emission nebula gets its color from ionized hydrogen, whereas the reflection nebula gets its color from billions of tiny grains of dust which are certainly "blowing in the wind".

I find the APOD irritating but interesting.

Ann

[Chris Peterson]

As Christian surmised, I'm not too happy with the non-blue appearance of the blue hue of the reflection nebula part of the APOD.

Let's compare the APOD with a picture that I like very much myself:

The Trifid Nebula. Credit: Image Credit & Copyright: Robert Edelmaier and Gabriele Gegenbauer

---

The Trifid Nebula. Credit: Emmanuel Astronomono

---

As you can see, the colors of Emmanuel Astronomono's picture are much more saturated than the colors of the APOD. For myself, I'm okay with a pale pink hue of the central emission nebula, but I definitely want a bluer version of the reflection nebula than what the APOD offers. To me it barely looks blue at all. Indeed, at first I didn't even realize that I was looking at the Trifid Nebula!

If you go to Robert Edelmaier and Gabriele Gegenbauer's website, you can see that they used not only RGB filters for their image, and not just RGB + Hα filters either, but RGB + Hα + OIII + SII filters. There is no way that you are going to get a good RGB color image from the use of all those filters. If all the filters have been used to detect nebulosity, then we must be dealing with a false color (or, as Chris would say, a mapped color) nebula.

We should note that the reflection nebula in the APOD is definitely larger (and also brighter) than the reflection nebula in Emmanuel Astronomono's image. My guess is that one or more of the narrowband filters have detected nebulosity at a larger distance from the central Trifid than RGB filters typically do. It wouldn't surprise me at all if some of the outermost nebulosity in the APOD is faint red SII.

We are definitely seeing much more red Hα than we usually do in the vicinity of the Trifid, at upper right and lower right.

In any case, the visually blue reflection nebula has been mixed with colors detected by narrowband filters, and the image has been processed so that the reflection nebula is a pale shade of gray, even beige.

An interesting aspect of the APOD is that the pink emission nebula looks smooth, whereas the "blue" reflection nebula looks extremely tousled, like a poor cat's or dog's wildly unkempt fur. Of course, the pink emission nebula gets its color from ionized hydrogen, whereas the reflection nebula gets its color from billions of tiny grains of dust which are certainly "blowing in the wind".

I find the APOD irritating but interesting.

Ann

This image doesn't do much for me. Partly because of the low contrast and low saturation, and partly because the stars have been suppressed... something easy to do these days, and which always results in images that lose all their aesthetic appeal to me. The depth of the image is interesting in how it brings out extended structure that we don't usually see with M20, but that's it... interesting. Not attractive.

[Ann]

This image doesn't do much for me. Partly because of the low contrast and low saturation, and partly because the stars have been suppressed... something easy to do these days, and which always results in images that lose all their aesthetic appeal to me. The depth of the image is interesting in how it brings out extended structure that we don't usually see with M20, but that's it... interesting. Not attractive.

It goes without saying that I dislike nebula images where stars have been suppressed. What's the point?

But look at the stellar background of Emmanuel Astronomono's image. Isn't it glorious?

---

Not only do we see "more or less foreground" stars of different luminosities and colors, but we also get a wonderfully rich background tapestry of small or distant mostly red and yellow, mostly somewhat reddened Milky Way stars.

Ann

[Chris Peterson]

This image doesn't do much for me. Partly because of the low contrast and low saturation, and partly because the stars have been suppressed... something easy to do these days, and which always results in images that lose all their aesthetic appeal to me. The depth of the image is interesting in how it brings out extended structure that we don't usually see with M20, but that's it... interesting. Not attractive.

It goes without saying that I dislike nebula images where stars have been suppressed. What's the point?

But look at the stellar background of Emmanuel Astronomono's image. Isn't it glorious?

---

Not only do we see "more or less foreground" stars of different luminosities and colors, but we also get a wonderfully rich background tapestry of small or distant mostly red and yellow, mostly somewhat reddened Milky Way stars.

Ann

And one I took. M20 is a jewel box of color... take away the jewels and what's left is just flat.
_

[Ann]

This image doesn't do much for me. Partly because of the low contrast and low saturation, and partly because the stars have been suppressed... something easy to do these days, and which always results in images that lose all their aesthetic appeal to me. The depth of the image is interesting in how it brings out extended structure that we don't usually see with M20, but that's it... interesting. Not attractive.

It goes without saying that I dislike nebula images where stars have been suppressed. What's the point?

But look at the stellar background of Emmanuel Astronomono's image. Isn't it glorious?

---

Not only do we see "more or less foreground" stars of different luminosities and colors, but we also get a wonderfully rich background tapestry of small or distant mostly red and yellow, mostly somewhat reddened Milky Way stars.

Ann

And one I took. M20 is a jewel box of color... take away the jewels and what's left is just flat.
_

Click to view full size image

Love your resolution of the small bright star cluster at the center of the Trifid Nebula! No, we don't see all the stars there, but we very clearly see two stars there, which is great! And definitely better than what Emmanuel Astronomono achieved - although he beats you when it comes to the Milky Way background.

(And to those reading this post: Don't click on Chris' image in my post. Click on Chris' image in Chris' post!)

Ann

[Ann]

This image doesn't do much for me. Partly because of the low contrast and low saturation, and partly because the stars have been suppressed... something easy to do these days, and which always results in images that lose all their aesthetic appeal to me. The depth of the image is interesting in how it brings out extended structure that we don't usually see with M20, but that's it... interesting. Not attractive.

It goes without saying that I dislike nebula images where stars have been suppressed. What's the point?

But look at the stellar background of Emmanuel Astronomono's image. Isn't it glorious?

---

Not only do we see "more or less foreground" stars of different luminosities and colors, but we also get a wonderfully rich background tapestry of small or distant mostly red and yellow, mostly somewhat reddened Milky Way stars.

Ann

And one I took. M20 is a jewel box of color... take away the jewels and what's left is just flat.
_

Click to view full size image

Love your resolution of the small bright star cluster at the center of the Trifid Nebula! No, we don't see all the stars there, but we very clearly see two stars there, which is great! Indeed, at full resolution we see other small blue-white stars close to the two bright ones.

You definitely did a better job at resolving the central cluster of the Trifid Nebula than what Emmanuel Astronomono achieved - although he beats you when it comes to the Milky Way background.

(And to those reading this post: Don't click on Chris' image in my post. Click on Chris' image in Chris' post!)

Ann

[Chris Peterson]

It goes without saying that I dislike nebula images where stars have been suppressed. What's the point?

But look at the stellar background of Emmanuel Astronomono's image. Isn't it glorious?

---

Not only do we see "more or less foreground" stars of different luminosities and colors, but we also get a wonderfully rich background tapestry of small or distant mostly red and yellow, mostly somewhat reddened Milky Way stars.

Ann

And one I took. M20 is a jewel box of color... take away the jewels and what's left is just flat.
_

Click to view full size image

Love your resolution of the small bright star cluster at the center of the Trifid Nebula! No, we don't see all the stars there, but we very clearly see two stars there, which is great! And definitely better than what Emmanuel Astronomono achieved - although he beats you when it comes to the Milky Way background.

(And to those reading this post: Don't click on Chris' image in my post. Click on Chris' image in Chris' post!)

Ann

M20 is a tricky target for me, because it's low in the sky and there's a tree blocking it about where it's passing highest. So I shoot it through the tree, and the result is those weird, JWST-like diffraction spikes around the bright stars, caused by tree branches!

[Ann]

M20 is a tricky target for me, because it's low in the sky and there's a tree blocking it about where it's passing highest. So I shoot it through the tree, and the result is those weird, JWST-like diffraction spikes around the bright stars, caused by tree branches!

I like diffraction spikes. But I think that those of JWST are too much.

Ann

[Chris Peterson]

M20 is a tricky target for me, because it's low in the sky and there's a tree blocking it about where it's passing highest. So I shoot it through the tree, and the result is those weird, JWST-like diffraction spikes around the bright stars, caused by tree branches!

I like diffraction spikes. But I think that those of JWST are too much.

Ann

So are those of Ponderosa pines. But you get what you get.

[Christian G.]

And one I took. M20 is a jewel box of color... take away the jewels and what's left is just flat.

M20.jpg (31.08 KiB) Viewed 6450 times

Very nice image! I like the deep tones and the clear split of the middle stars.

[JimB]

The second law of thermodynamics says that the entropy of a system is always increasing, and so eventually everything will be in a state of max disorder and "evenly mixed", but looking scenes like the Triffid Nebula (estimated age 300,000 years) it's difficult to imagine that the universe will ever be evenly mixed.

To be fair, that's like putting a drop of food coloring in a glass of water and after one second saying it's difficult to imagine you'll ever see an even mixture...

It's not just the timescale, it's the difficulty in accounting for all the interactions between the different forces. Gravity pulls stuff together, stars create solar winds, quasars spew out jets, magnetic fields pull stuff together into filaments, plus dark matter pulling and dark energy pushing - all like a vast game of pinball.

[Chris Peterson]

The second law of thermodynamics says that the entropy of a system is always increasing, and so eventually everything will be in a state of max disorder and "evenly mixed", but looking scenes like the Triffid Nebula (estimated age 300,000 years) it's difficult to imagine that the universe will ever be evenly mixed.

To be fair, that's like putting a drop of food coloring in a glass of water and after one second saying it's difficult to imagine you'll ever see an even mixture...

It's not just the timescale, it's the difficulty in accounting for all the interactions between the different forces. Gravity pulls stuff together, stars create solar winds, quasars spew out jets, magnetic fields pull stuff together into filaments, plus dark matter pulling and dark energy pushing - all like a vast game of pinball.

But the only structure we see that is long lasting is created by gravity, and it ultimately wins by turning everything with mass into black holes, and those evaporate, and all that's left is a sea of photons and neutrinos. Uniform and cold. And the ultimate end of the Universe in this scenario is one where the energy is uniformly distributed and therefore no work can happen.

[VictorBorun]

The second law of thermodynamics says that the entropy of a system is always increasing, and so eventually everything will be in a state of max disorder and "evenly mixed", but looking scenes like the Triffid Nebula (estimated age 300,000 years) it's difficult to imagine that the universe will ever be evenly mixed.

...I agree with you. The area around the Trifid Nebula (bottom left Lagoon Nebula) also seems to be quite dynamic in the radio (white) and IR (red/blue) frequency range. But what we see here are only fragments of the last few hundred thousand years. Nothing in astronomical terms...
Cosmic flowers that quickly bloom but also quickly fade again.

Click to view full size image 1 or image 2

Original datra: NASA/ESA Radio (RACS) IR (GLIMPSE) jac berne (flickr)


See also corparison optical/IR (SST): https://viewspace.org/resources/invisib ... fid_nebula

Hard to believe this Radio (RACS) / IR (GLIMPSE) image hang-over is fitted. The star field jumps like crazy