APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

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VictorBorun
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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by VictorBorun » Tue Jan 25, 2022 12:32 am

johnnydeep wrote: Mon Jan 24, 2022 9:30 pm This jet (bottom image) from a young star bears a passing structural resemblance to the Witch Head Nebula: The image is from https://esahubble.org/images/opo9524a/, and it suggests the jet is monodirectional:
Bottom image
This view of a three trillion mile-long jet called HH-47 reveals a very complicated jet pattern that indicates the star (hidden inside a dust cloud near the left edge of the image) might be wobbling, possibly caused by the gravitational pull of a companion star.
Can Witch Head Nebula be an aging Herbig–Haro object? Say, 10 ky old one?

Much of the wind eating away the cloud in the path of the jets is from Rigel or other Orion's giants, all north-east in the posted picture.
But some wind must blow from the HH object's core, so there should be some skirt-shape features giving away the direction of the wind from the core and so the position of the core along the joined path of the pair of the jets.
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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by neufer » Tue Jan 25, 2022 2:17 am

VictorBorun wrote: Tue Jan 25, 2022 12:32 am
johnnydeep wrote: Mon Jan 24, 2022 9:30 pm

This jet (bottom image) from a young star bears a passing structural resemblance to the Witch Head Nebula. (The image is from https://esahubble.org/images/opo9524a/, and it suggests the jet is monodirectional.)
Bottom imageThis view of a three trillion mile-long jet called HH-47 reveals a very complicated jet pattern that indicates the star (hidden inside a dust cloud near the left edge of the image) might be wobbling, possibly caused by the gravitational pull of a companion star.
Can Witch Head Nebula be an aging Herbig–Haro object? Say, 10 ky old one?
  • Let's ask the Wizardkipedia ... the Wizardkipedia will know:
https://en.wikipedia.org/wiki/IC_2118 wrote:
Click to play embedded YouTube video.
<<IC 2118 (also known as Witch Head Nebula due to its shape) is an extremely faint reflection nebula believed to be an ancient supernova remnant or gas cloud illuminated by nearby supergiant star Rigel in the constellation of Orion. It lies in the Orion constellation, about 900 light-years from Earth. The nature of the dust particles, reflecting blue light better than red, is a factor in giving the Witch Head its blue color. Radio observations show substantial carbon monoxide emission throughout parts of IC 2118, an indicator of the presence of molecular clouds and star formation in the nebula. In fact candidates for pre-main sequence stars and some classic T-Tauri stars have been found deep within the nebula.

The molecular clouds of IC 2118 are probably juxtaposed to the outer boundaries of the vast Orion-Eridanus bubble, a giant supershell of molecular hydrogen blown by the high mass stars of the Orion OB1 association. As the supershell expands into the interstellar medium, favorable circumstances for star formation occur. IC 2118 is located in one such area. The wind blown appearance and cometary shape of the bright reflection nebula is highly suggestive of a strong association with the high mass luminous stars of Orion OB1. The fact that the heads of the cometary clouds of IC2118 point northeast towards the association is strong support of that relationship.>>
https://en.wikipedia.org/wiki/Orion%E2%80%93Eridanus_Superbubble wrote: The Orion–Eridanus Superbubble or Eridanus Soft X-ray Enhancement is a superbubble located west of the Orion Nebula. The region is formed from overlapping supernova remnants that may be associated with the Orion OB1 stellar association; the bubble is approximately 1200 ly across. It is the nearest superbubble to the Local Bubble containing the Sun, with the respective shock fronts being about 500 ly apart.

The structure was discovered from 21 cm radio observations by Carl Heiles and interstellar optical emission line observations by Reynolds and Ogden in the 1970s.
Art Neuendorffer

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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by VictorBorun » Tue Jan 25, 2022 3:01 am

neufer wrote: Tue Jan 25, 2022 2:17 am
https://en.wikipedia.org/wiki/IC_2118 wrote: favorable circumstances for star formation
well, why can't Witch Head Nebula be an aging HH object (10 ky old) in the thick of giant stars' bubble wall?

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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by neufer » Tue Jan 25, 2022 4:16 am

VictorBorun wrote: Tue Jan 25, 2022 3:01 am
neufer wrote: Tue Jan 25, 2022 2:17 am
https://en.wikipedia.org/wiki/IC_2118 wrote:
favorable circumstances for star formation
well, why can't Witch Head Nebula be an aging HH object (10 ky old) in the thick of giant stars' bubble wall?
It is not the sort of environment I would expect:
https://en.wikipedia.org/wiki/IC_2118 wrote:
Candidates for pre-main sequence stars and some classic T-Tauri stars have been found deep within the nebula.
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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by VictorBorun » Tue Jan 25, 2022 4:58 am

neufer wrote: Tue Jan 25, 2022 4:16 am
VictorBorun wrote: Tue Jan 25, 2022 3:01 am why can't Witch Head Nebula be an aging HH object (10 ky old) in the thick of giant stars' bubble wall?
It is not the sort of environment I would expect:
https://en.wikipedia.org/wiki/IC_2118 wrote: Candidates for pre-main sequence stars and some classic T-Tauri stars have been found deep within the nebula.
Do I get it right: a star is welcome to emit a pair of jets at 2 moments:
when it's a proto-star of 1 Sun mass using an accretion disk in the core of proto-planets dusty disk to make make a pair of jets of 30 Earth mass
when it's a SuperNova of 100 Suns mass using a shedded disk to make a pair of jets of 3 Suns mass

Now the Witch Head Nebula is rather Super-Nova scale, is not it?

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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by Ann » Tue Jan 25, 2022 5:01 am

Chris Peterson wrote: Mon Jan 24, 2022 9:21 pm
Ann wrote: Mon Jan 24, 2022 9:14 pm
Chris Peterson wrote: Mon Jan 24, 2022 2:55 pm
As always, of course, processing is everything. There's really no such thing as "real" color in objects which are too dim for us to perceive color.
Chris, I asked you before if you think that reflection nebulas do display real colors in such a way that they scatter more blue than red light our way, or more red than blue light. You haven't answered.
I thought I did answer that above. The answer is neither. Or both, if you prefer. Scattering requires a low density dust cloud. A high density cloud is opaque, and there is almost no scattering. Such a cloud reflects light, and is therefore brown (unsaturated red). A low density cloud doesn't reflect much, but is an efficient scatterer. So it appears blue.

I don't see much blue in the Witch Head. Mostly I see reflected light, fairly unsaturated brown (like a warm gray).
That's my point, Chris. There is less blue than usual in the Witch Head Nebula in today's APOD. Usually there is more blue there in pictures - because there is more blue there.

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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by Chris Peterson » Tue Jan 25, 2022 1:39 pm

Ann wrote: Tue Jan 25, 2022 5:01 am
Chris Peterson wrote: Mon Jan 24, 2022 9:21 pm
Ann wrote: Mon Jan 24, 2022 9:14 pm

Chris, I asked you before if you think that reflection nebulas do display real colors in such a way that they scatter more blue than red light our way, or more red than blue light. You haven't answered.
I thought I did answer that above. The answer is neither. Or both, if you prefer. Scattering requires a low density dust cloud. A high density cloud is opaque, and there is almost no scattering. Such a cloud reflects light, and is therefore brown (unsaturated red). A low density cloud doesn't reflect much, but is an efficient scatterer. So it appears blue.

I don't see much blue in the Witch Head. Mostly I see reflected light, fairly unsaturated brown (like a warm gray).
That's my point, Chris. There is less blue than usual in the Witch Head Nebula in today's APOD. Usually there is more blue there in pictures - because there is more blue there.

Ann
I don't see much blue in other images, either.
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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by Ann » Tue Jan 25, 2022 2:12 pm

Chris Peterson wrote: Tue Jan 25, 2022 1:39 pm
Ann wrote: Tue Jan 25, 2022 5:01 am
Chris Peterson wrote: Mon Jan 24, 2022 9:21 pm
I thought I did answer that above. The answer is neither. Or both, if you prefer. Scattering requires a low density dust cloud. A high density cloud is opaque, and there is almost no scattering. Such a cloud reflects light, and is therefore brown (unsaturated red). A low density cloud doesn't reflect much, but is an efficient scatterer. So it appears blue.

I don't see much blue in the Witch Head. Mostly I see reflected light, fairly unsaturated brown (like a warm gray).
That's my point, Chris. There is less blue than usual in the Witch Head Nebula in today's APOD. Usually there is more blue there in pictures - because there is more blue there.

Ann
I don't see much blue in other images, either.
You may check out several photos of the Witch Head Nebula here. I find all the images relatively blue, except the fifth image, which is dominated by a very red background. The red background of that image resembles the background of the APOD, and in my opinion, this emphasis on red hydrogen alpha background light (which is not strong near Rigel) alters the color balance of the entire image and risks making the Witch Head Nebula look almost completely non-blue.


The image above is a favorite of mine. We can clearly see that only some parts of the Witch Head Nebula scatters blue light, while other parts appear gray or brown. Nevertheless, to me this nebula, when it looks the way it looks in the picture above, is clearly more blue than red.

If I know you, you remain perfectly unmoved by my arguments! That's okay, because I'm not really trying to convince you, and instead I'm arguing for the benefit of other members of (and visitors of) Starship Asterisk*.

Bear in mind that I have never said that the Witch Head Nebula is very blue. Indeed, and as you can see from the picture I posted, it is not even all blue in the first place. I'd describe the Witch Head Nebula as moderately blue, but in my opinion (and in the opinion of more or less everyone who writes about it on the net) the Witch Head Nebula is indeed more blue than red. However, if a photographer emphasizes the red background of this general area, and brings out red light more than blue light, then there is an increasing likelihood that the Witch Head Nebula is hardly going to look blue at all.

And now I've got nothing more to add!

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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by Chris Peterson » Tue Jan 25, 2022 2:22 pm

Ann wrote: Tue Jan 25, 2022 2:12 pm
Chris Peterson wrote: Tue Jan 25, 2022 1:39 pm
Ann wrote: Tue Jan 25, 2022 5:01 am

That's my point, Chris. There is less blue than usual in the Witch Head Nebula in today's APOD. Usually there is more blue there in pictures - because there is more blue there.

Ann
I don't see much blue in other images, either.
You may check out several photos of the Witch Head Nebula here. I find all the images relatively blue, except the fifth image, which is dominated by a very red background. The red background of that image resembles the background of the APOD, and in my opinion, this emphasis on red hydrogen alpha background light (which is not strong near Rigel) alters the color balance of the entire image and risks making the Witch Head Nebula look almost completely non-blue.


The image above is a favorite of mine. We can clearly see that only some parts of the Witch Head Nebula scatters blue light, while other parts appear gray or brown. Nevertheless, to me this nebula, when it looks the way it looks in the picture above, is clearly more blue than red.

If I know you, you remain perfectly unmoved by my arguments! That's okay, because I'm not really trying to convince you, and instead I'm arguing for the benefit of other members of (and visitors of) Starship Asterisk*.

Bear in mind that I have never said that the Witch Head Nebula is very blue. Indeed, and as you can see from the picture I posted, it is not even all blue in the first place. I'd describe the Witch Head Nebula as moderately blue, but in my opinion (and in the opinion of more or less everyone who writes about it on the net) the Witch Head Nebula is indeed more blue than red. However, if a photographer emphasizes the red background of this general area, and brings out red light more than blue light, then there is an increasing likelihood that the Witch Head Nebula is hardly going to look blue at all.

And now I've got nothing more to add!

Ann
I disagree. I would not call that a blue nebula. It is clearly dominated by brown reflection, with just a little bit of blue scatter from the outer shell.
Chris

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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by neufer » Tue Jan 25, 2022 3:38 pm

VictorBorun wrote: Tue Jan 25, 2022 4:58 am
neufer wrote: Tue Jan 25, 2022 4:16 am
VictorBorun wrote: Tue Jan 25, 2022 3:01 am why can't Witch Head Nebula be an aging HH object (10 ky old) in the thick of giant stars' bubble wall?
It is not the sort of environment I would expect:
https://en.wikipedia.org/wiki/IC_2118 wrote:
Candidates for pre-main sequence stars and some classic T-Tauri stars have been found deep within the nebula.
Do I get it right: a star is welcome to emit a pair of jets at 2 moments:
when it's a proto-star of 1 Sun mass using an accretion disk in the core of proto-planets dusty disk to make make a pair of jets of 30 Earth mass
when it's a SuperNova of 100 Suns mass using a shedded disk to make a pair of jets of 3 Suns mass

Now the Witch Head Nebula is rather Super-Nova scale, is not it?
Regardless of scale, jets provide a valuable service in dispersing angular momentum in order to allow for material collapse into: stars, supernova, black holes, etc..

On the other hand, these same jets also induce vortices whose angular momentum complicates any secondary material collapse into stars etc.

Hence, jets are not the sort of environment I would expect to be:
https://en.wikipedia.org/wiki/IC_2118 wrote:
Candidates for pre-main sequence stars and some classic T-Tauri stars that have been found deep within the Witch Head Nebula.
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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by VictorBorun » Tue Jan 25, 2022 4:40 pm

neufer wrote: Tue Jan 25, 2022 3:38 pm On the other hand, these same jets also induce vortices whose angular momentum complicates any secondary material collapse into stars etc.
Hence, jets are not the sort of environment I would expect to be:
So, when a giant going blue dwarf sheds some matter in jets they won't become proto-star material until lose their spin by colliding with other bubbles or something.
If the Witch Head Nebula were a pair of jets 10 ky old then the spin would have discouraged any starbirth so far.

By the way, however blue and scattering, the Witch Head Nebula must also emit some Hα red to measure Doppler's shift and to directly (dis)prove the spinning.

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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by Chris Peterson » Tue Jan 25, 2022 5:02 pm

VictorBorun wrote: Tue Jan 25, 2022 4:40 pm
neufer wrote: Tue Jan 25, 2022 3:38 pm On the other hand, these same jets also induce vortices whose angular momentum complicates any secondary material collapse into stars etc.
Hence, jets are not the sort of environment I would expect to be:
So, when a giant going blue dwarf sheds some matter in jets they won't become proto-star material until lose their spin by colliding with other bubbles or something.
If the Witch Head Nebula were a pair of jets 10 ky old then the spin would have discouraged any starbirth so far.

By the way, however blue and scattering, the Witch Head Nebula must also emit some Hα red to measure Doppler's shift and to directly (dis)prove the spinning.
Doppler measurements can be made from lots of other emission sources than hydrogen, and can be seen in reflection spectra, as well. Or in non-optical wavelengths.
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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by JohnD » Tue Jan 25, 2022 5:13 pm

Chris Peterson wrote: Mon Jan 24, 2022 6:49 pm
JohnD wrote: Mon Jan 24, 2022 6:38 pm
Chris Peterson wrote: Mon Jan 24, 2022 3:11 pm

Sorry, I see no resemblance between those things and this dusty nebula. I see no evidence of a jet here.
OK, Chris, yiou are the Astronomer. Please teach me! Why is this "dusty", and not a jet? It is certainly jet shaped.
I disagree that it is "jet shaped". It looks like a hundred other dense molecular clouds. It does not have the tenuous look of a jet.
But, Chris......! Speechless! The image of this nebula shown in the Apod itself looks like a jet, narrow base, expanding tip!

And I'm not alone in not being unable to understand your denial - Johnnydeep and VictorBourne have made similar comments to mine, in particular asking if this could be part of a HerbigHaro. Please, Chris, lead the tutorial, teach us, not just tell us we are wrong!

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Re: APOD: Rigel and the Witch Head Nebula (2022 Jan 24)

Post by Chris Peterson » Tue Jan 25, 2022 5:17 pm

JohnD wrote: Tue Jan 25, 2022 5:13 pm
Chris Peterson wrote: Mon Jan 24, 2022 6:49 pm
JohnD wrote: Mon Jan 24, 2022 6:38 pm

OK, Chris, yiou are the Astronomer. Please teach me! Why is this "dusty", and not a jet? It is certainly jet shaped.
I disagree that it is "jet shaped". It looks like a hundred other dense molecular clouds. It does not have the tenuous look of a jet.
But, Chris......! Speechless! The image shown in the Apod itself looks like a jet, narrow base, expanding tip!
Every jet image I've seen features a tenuous stream that shows lots of shock structures. This appears to be a dense molecular cloud being eroded by stellar winds. Apples and oranges visually.
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