APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

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APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by APOD Robot » Tue Feb 27, 2024 5:06 am

Image Supernova Remnant Simeis 147

Explanation: It's easy to get lost following the intricate, looping, and twisting filaments of supernova remnant Simeis 147. Also cataloged as Sharpless 2-240, the filamentary nebula goes by the popular nickname the Spaghetti Nebula. Seen toward the boundary of the constellations of the Bull (Taurus) and the Charioteer (Auriga), the impressive gas structure covers nearly 3 degrees on the sky, equivalent to 6 full moons. That's about 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years. This composite image includes data taken through narrow-band filters isolating emission from hydrogen (red) and oxygen (blue) glowing gas. The supernova remnant has an estimated age of about 40,000 years, meaning light from this massive stellar explosion first reached the Earth when woolly mammoths roamed free. Besides the expanding remnant, this [url=https://mfrost.typepad.com/photos/uncat ... terror.jpg" >cosmic catastrophe<a/> left behind a <a href="https://en.wikipedia.org/wiki/Pulsar]pulsar[/url]: a spinning neutron star that is the remnant of the original star's core.

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Ann » Tue Feb 27, 2024 7:15 am

Simeis147_Vetter_960[1].jpg
Supernova Remnant Simeis 147
Image Credit & Copyright: Stéphane Vetter (Nuits sacrées)
The Flying Spaghetti Monster annotated Niklas Jansson.png
The Flying Spaghetti Monster. Credit: Niklas Jansson.
Blotting out of private parts: Ann


Who knew that the Flying Spaghetti Monster really exists, and that His Noodliness is the spaghettified supernova remnant of Simeis 147?
Eh, spaghettified, not really!

On a slightly more serious note, pay attention to the outer bluish strands of Simeis 147. These are typical of supernova remnants, as the gaseous debris that was flung out of the "ground zero" of the explosion crashes into the surrounding interstellar medium and makes it glow blue-green from doubly ionized oxygen, OIII.

Other supernova remnants show similar cyan-glowing shock fronts:


Supernova remnants are highly ionized at their edges, where they typically glow blue-green. "Normal" emission nebulas are the other way round: they create OIII emission near their centers and less energetic forms of ionizations, such as Hα, further out. (Oops, "farther" out?)


And speaking of farther and further...hmm, let's call the whole thing off?

Click to play embedded YouTube video.

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Locutus76 » Tue Feb 27, 2024 11:56 am

So we have the Spaghetti Nebula, surrounding a neutron star that in its interior has a spaghetti phase of exotic matter, along other edible phases like gnocchi, lasagna and Swiss cheese. Tasty environment!

zendae1

Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by zendae1 » Tue Feb 27, 2024 2:31 pm

Hi Ann,
So whatever you (or anyone) can answer, a couple down-to-earth questions: 1) Considering the distance, about how wide are those filaments? 2) If we were right "next" to one, would we see anything? Do we need to be far away to see the nebula, or its brightness? 3) Is the temperature theoretically hot to the touch anywhere in the nebula? Is the nebula hot? Are there tiny absolute zero areas right next to tiny extreme hot areas? 3) Does each filament have it's own proprietary source or do many propagate from single sources, or do they propagate each other?

As an English major, "farther" is correct; it relates to actual physical or concrete distance, whereas "further" denotes figurative or abstract distance. I just had this conversation yesterday, oddly enough.

I keep reading how large these nebula actually are in the sky. It would be neat to see an AI rendition of our starry skies replete with all the nebula we can't see.

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Chris Peterson » Tue Feb 27, 2024 2:42 pm

zendae1 wrote: Tue Feb 27, 2024 2:31 pm Hi Ann,
So whatever you (or anyone) can answer, a couple down-to-earth questions: 1) Considering the distance, about how wide are those filaments? 2) If we were right "next" to one, would we see anything? Do we need to be far away to see the nebula, or its brightness? 3) Is the temperature theoretically hot to the touch anywhere in the nebula? Is the nebula hot? Are there tiny absolute zero areas right next to tiny extreme hot areas? 3) Does each filament have it's own proprietary source or do many propagate from single sources, or do they propagate each other?

As an English major, "farther" is correct; it relates to actual physical or concrete distance, whereas "further" denotes figurative or abstract distance. I just had this conversation yesterday, oddly enough.

I keep reading how large these nebula actually are in the sky. It would be neat to see an AI rendition of our starry skies replete with all the nebula we can't see.
These filaments are very dim. The brighter ones are visible to the eye through a telescope, barely, and largely because we detect the faint contrast with the surrounds. If we were closer, it would not be brighter, but we'd lose that contrast. If we were at the nebula, we'd see nothing.

The gas is very hot, or it would not be ionized. But if we were there with a thermometer, it would read just a few K, because the medium is too thin to transfer significant heat. (The nebular filaments could be described as a very hard vacuum.) Compare it to the thermosphere, the part of the atmosphere where the ISS orbits, where the thin gas exists at 2000°C or more, but can't heat the skin of the ISS. The concept of "temperature" is a bit different in near-vacuums, where we think of it more in terms of the energy carried by individual particles.

(And to revisit the previous conversation, "further" is always correct; it is "farther" that you can get wrong. Indeed, if we were in England, most stylebooks would recommend "further" in all cases, including physical distance. So I think the best advice for our non-native-English speakers like Ann is to always use "further" and not waste time figuring it out beyond that!)
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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Ann » Tue Feb 27, 2024 3:47 pm

zendae1 wrote: Tue Feb 27, 2024 2:31 pm Hi Ann,
So whatever you (or anyone) can answer, a couple down-to-earth questions: 1) Considering the distance, about how wide are those filaments? 2) If we were right "next" to one, would we see anything? Do we need to be far away to see the nebula, or its brightness? 3) Is the temperature theoretically hot to the touch anywhere in the nebula? Is the nebula hot? Are there tiny absolute zero areas right next to tiny extreme hot areas? 3) Does each filament have it's own proprietary source or do many propagate from single sources, or do they propagate each other?

As an English major, "farther" is correct; it relates to actual physical or concrete distance, whereas "further" denotes figurative or abstract distance. I just had this conversation yesterday, oddly enough.

I keep reading how large these nebula actually are in the sky. It would be neat to see an AI rendition of our starry skies replete with all the nebula we can't see.
I can't do AI for you, but I might show you something:

Nebulas in Aurigae on a map from Cartes de Ciel J P Metsavainio.png
Nebulas in Aurigae. Note Simeis 147 at lower left.
Credit: J-P Metsavainio

Simeis 147 is really quite big in the sky. Compare its size to constellation Auriga itself.

Please note that there is another supernova remnant in Auriga, the Rice Hat Nebula or Sharpless 224.

nRBdS8BgB3GY_1824x0_n1wMX-gx[1].jpg
The Rice Hat Nebula can be identified as a supernova remnant
because of its blue-green edges. The other nebula, Sharpless 223,
lacks blue edges and is not a supernova remnant. Credit: Göran Nilsson.

The Rice Hat nebula is located in the upper right part of Auriga.

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Case » Tue Feb 27, 2024 7:37 pm

Chris Peterson wrote: Tue Feb 27, 2024 2:42 pmThese filaments are very dim. The brighter ones are visible to the eye through a telescope, barely, and largely because we detect the faint contrast with the surrounds. If we were closer, it would not be brighter, but we'd lose that contrast. If we were at the nebula, we'd see nothing.
Analogous to that: If our solar system is in a nebulous bubble, or void for that matter, would we know? How can we tell?

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Chris Peterson » Tue Feb 27, 2024 7:47 pm

Case wrote: Tue Feb 27, 2024 7:37 pm
Chris Peterson wrote: Tue Feb 27, 2024 2:42 pmThese filaments are very dim. The brighter ones are visible to the eye through a telescope, barely, and largely because we detect the faint contrast with the surrounds. If we were closer, it would not be brighter, but we'd lose that contrast. If we were at the nebula, we'd see nothing.
Analogous to that: If our solar system is in a nebulous bubble, or void for that matter, would we know? How can we tell?
Visually, I doubt we would know. We could probably determine it with modern instruments, in the same way that we now understand ourselves to be inside the Local Interstellar Cloud, which is itself inside the Local Bubble- both being slight variations in the interstellar medium we can observe in UV, in deep optical, and with particle counting instruments on space probes, but which were completely unknown before those tools were available.
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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Roy » Tue Feb 27, 2024 8:16 pm

All the nebulae are visible because they are ionized gas atoms. They have absorbed energy and kicked off electrons. So where is that flood of electrons to be found?

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by johnnydeep » Tue Feb 27, 2024 8:38 pm

Ann wrote above:
Supernova remnants are highly ionized at their edges, where they typically glow blue-green. "Normal" emission nebulas are the other way round: they create OIII emission near their centers and less energetic forms of ionizations, such as Hα, further out.
Why is this, exactly?
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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Chris Peterson » Tue Feb 27, 2024 10:05 pm

Roy wrote: Tue Feb 27, 2024 8:16 pm All the nebulae are visible because they are ionized gas atoms. They have absorbed energy and kicked off electrons. So where is that flood of electrons to be found?
We get a photon emitted when an electron recombines with an ionized atom. An energetic region like this consists of a cloud of ionized gas (just protons in the case of hydrogen) and free electrons. For typical HII regions, you can calculate a photoionization rate and come up with a photoionization time of about 3 years. You can also calculate a recombination rate to get a typical recombination time of about 10,000 years. In other words, a neutral hydrogen atom will get ionized once every 3 years, and recombine with an electron (and produce a photon) every 10,000 years. Which tells us that the hydrogen in an HII region is mostly ionized, given a short time to ionize and a long time to recombine. Of course, these numbers vary quite a bit based on the flux of ionizing photons from the energizing star or stars, and the density of the nebula. The free electrons exist in a complex environment where they are scattering off each other, which is part of what influences the long recombination time. Things also get complicated in dusty nebulas, where the dust inside the plasma becomes charged and interacts with the free protons (or larger atoms in the case of oxygen and other common interstellar elements) and electrons.
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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by johnnydeep » Tue Feb 27, 2024 10:38 pm

Chris Peterson wrote: Tue Feb 27, 2024 10:05 pm
Roy wrote: Tue Feb 27, 2024 8:16 pm All the nebulae are visible because they are ionized gas atoms. They have absorbed energy and kicked off electrons. So where is that flood of electrons to be found?
We get a photon emitted when an electron recombines with an ionized atom. An energetic region like this consists of a cloud of ionized gas (just protons in the case of hydrogen) and free electrons. For typical HII regions, you can calculate a photoionization rate and come up with a photoionization time of about 3 years. You can also calculate a recombination rate to get a typical recombination time of about 10,000 years. In other words, a neutral hydrogen atom will get ionized once every 3 years, and recombine with an electron (and produce a photon) every 10,000 years. Which tells us that the hydrogen in an HII region is mostly ionized, given a short time to ionize and a long time to recombine. Of course, these numbers vary quite a bit based on the flux of ionizing photons from the energizing star or stars, and the density of the nebula. The free electrons exist in a complex environment where they are scattering off each other, which is part of what influences the long recombination time. Things also get complicated in dusty nebulas, where the dust inside the plasma becomes charged and interacts with the free protons (or larger atoms in the case of oxygen and other common interstellar elements) and electrons.
Wow, that was an extremely lucid - despite still being very technical! - explanation - Thanks!
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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Ann » Wed Feb 28, 2024 8:17 am

johnnydeep wrote: Tue Feb 27, 2024 8:38 pm Ann wrote above:
Supernova remnants are highly ionized at their edges, where they typically glow blue-green. "Normal" emission nebulas are the other way round: they create OIII emission near their centers and less energetic forms of ionizations, such as Hα, further out.
Why is this, exactly?
As you know, Johnny, if you want an exact answer, you must ask Chris. But I'll have a go.

Bear in mind that we - or at least I - talk about very specific visible wavelengths when I talk about degrees of ionizations of nebulas. Basically I just talk about OIII, at 501 nm, a greenish-cyan hue that is often mapped as blue, and Hα, at 656 nm, which our eyes see as red.

As humans, we are interested in - or attracted to? - light that we can see. OIII and Hα are wavelengths of light that we can see (even though it's basically impossible for our eyes to see the very faint red Hα light of nebulas, even though we can often see this light as gray).

But there are so many other types of ionization out there, and hydrogen itself is capable of producing ionized wavelengths that we absolutely can't see:


Let me give you another example of how wavelengths matter.


As for emission nebulas and supernova remnants, I talk about the energy that ionizes hydrogen to hydrogen alpha in the Balmer series and oxygen to doubly ionized oxygen, OIII, in an oxygen series of ionization whose designation I don't know.

Consider the Crab Nebula, a very young supernova remnant. Let's look at it in two versions, one pure RGB and one OIII/Hα/SII:


The blue color in the HαOIIISII image shows us the energy that is created as the supernova debris slams into the surrounding medium. However, much higher energy is generated in the center of the Crab Nebula:

Eric Mack of CNET wrote about the Crab Nebula:

The observatory high in the Himalayan foothills discovered a photon of energy from the nebula measuring one quadrillion electron volts, a level so high that it points to the existence of a natural particle accelerator near the center of the Crab Nebula that is about one-tenth the size of our entire solar system. Such a system would be able to energize electrons to levels 20,000 times that which the accelerators constructed on Earth at places like CERN can accomplish.
Enormous amounts of energy are created inside the Crab Nebula, but this ultra-high energy does not produce that much visible light. The yellow-white light seen in the RGB picture of the Crab Nebula would be synchrotron emission, which is generated as electron whirl around in a magnetic field at nearly the speed of light. The way I have understood it, synchrotron emission radiates at all wavelengths, which would create a neutral overall color.

So the way I have understood it, the outer edges of expanding supernova remnants - and bear in mind that they are indeed expanding quite fast! - slam into the surrounding interstellar medium, and the "impact" produces just the amount of energy that ionizes oxygen and makes it glow blue-green.

As for emission nebulas, they expand, but they certainly don't expand very fast. They do push gas away from the hot stars and often make it pile up in a rim around the nebula, but they don't do it with enough force to ionize OIII. Instead, the amount of energy that ionizes oxygen is typically found in the relative vicinity of the hot main sequence or giant stars near the center of emission nebulas.

You must also consider the nature of the matter that is being pushed in supernova remnants and in emission nebulas as well as the forces that are pushing it. In emission nebulas, hydrogen gas is being pushed by stellar winds and ultraviolet emission from hot stars, but in supernova remnants, clumps of stellar matter are being ejected like projectiles at supersonic speeds following a titanic blast.

Emission nebulas are much less violent than SNRs, but there are forces pushing on the gas in them, too.


The picture by Andreas Papp looks like an RGB(Hα) image to me. I'd say that it has been processed to show the "thinness" of the central part of the nebula and the presence of bluish light there, which comes from both reflected starlight and OIII. (In most RGB images, the red Hα is too bright for the bluish OIII and reflected starlight to show up very much.)

You can also see how much of the hydrogen has been pushed to the rim of the nebula, where it looks very thick. Here it glows red from Hα, not blue or green from OIII.

One type of objects that often creates huge amounts of OIII is the central stars of planetary nebulas. These burnt-out cinders are very hot indeed, typically much hotter than main sequence and giant O-type stars like the O-type stars of Orion, and they emit copious ultraviolet light, which strongly ionizes oxygen and makes it glow blue-green. You are not likely to find many other nebulas in the sky that are so visually colorful.


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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Christian G. » Wed Feb 28, 2024 1:30 pm

Chris Peterson wrote: Tue Feb 27, 2024 10:05 pm
Roy wrote: Tue Feb 27, 2024 8:16 pm
a typical recombination time of about 10,000 years.
I had no idea it took so long for recombination to occur! So if an energetic star magically popped up in the middle of a neutral hydrogen cloud, the latter would start glowing in visible light only thousands of years later??
(what about instances where ionization is not the stripping away but the addition of an electron to an atom, does it emit a photon instantly then?)

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Chris Peterson » Wed Feb 28, 2024 1:39 pm

Christian G. wrote: Wed Feb 28, 2024 1:30 pm
Chris Peterson wrote: Tue Feb 27, 2024 10:05 pm
Roy wrote: Tue Feb 27, 2024 8:16 pm
a typical recombination time of about 10,000 years.
I had no idea it took so long for recombination to occur! So if an energetic star magically popped up in the middle of a neutral hydrogen cloud, the latter would start glowing in visible light only thousands of years later??
(what about instances where ionization is not the stripping away but the addition of an electron to an atom, does it emit a photon instantly then?)
That's a tricky question. The ionization and recombination times are statistical values, like radioactive half-lives. So you need to think in terms of a distribution curve applied to a huge number of starting neutral atoms. What we would have to calculate is the time to equilibrium (the state that actual nebulas are in), and the shape of the curve ramping up to that point. I don't know (without doing more math than I feel like engaging in early in the morning) what that curve or time looks like, but I'm pretty sure we'd start detecting a glow fairly quickly.
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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Christian G. » Wed Feb 28, 2024 3:00 pm

Chris Peterson wrote: Wed Feb 28, 2024 1:39 pm
Christian G. wrote: Wed Feb 28, 2024 1:30 pm
Chris Peterson wrote: Tue Feb 27, 2024 10:05 pm

a typical recombination time of about 10,000 years.
I had no idea it took so long for recombination to occur! So if an energetic star magically popped up in the middle of a neutral hydrogen cloud, the latter would start glowing in visible light only thousands of years later??
(what about instances where ionization is not the stripping away but the addition of an electron to an atom, does it emit a photon instantly then?)
That's a tricky question. The ionization and recombination times are statistical values, like radioactive half-lives. So you need to think in terms of a distribution curve applied to a huge number of starting neutral atoms. What we would have to calculate is the time to equilibrium (the state that actual nebulas are in), and the shape of the curve ramping up to that point. I don't know (without doing more math than I feel like engaging in early in the morning) what that curve or time looks like, but I'm pretty sure we'd start detecting a glow fairly quickly.
Thanks for your answer. You definitely beat my google searches!

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by zendae1 » Wed Feb 28, 2024 4:02 pm

Thanks Chris and Ann!

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Chris Peterson » Wed Feb 28, 2024 4:10 pm

Christian G. wrote: Wed Feb 28, 2024 3:00 pm
Chris Peterson wrote: Wed Feb 28, 2024 1:39 pm
Christian G. wrote: Wed Feb 28, 2024 1:30 pm
I had no idea it took so long for recombination to occur! So if an energetic star magically popped up in the middle of a neutral hydrogen cloud, the latter would start glowing in visible light only thousands of years later??
(what about instances where ionization is not the stripping away but the addition of an electron to an atom, does it emit a photon instantly then?)
That's a tricky question. The ionization and recombination times are statistical values, like radioactive half-lives. So you need to think in terms of a distribution curve applied to a huge number of starting neutral atoms. What we would have to calculate is the time to equilibrium (the state that actual nebulas are in), and the shape of the curve ramping up to that point. I don't know (without doing more math than I feel like engaging in early in the morning) what that curve or time looks like, but I'm pretty sure we'd start detecting a glow fairly quickly.
Thanks for your answer. You definitely beat my google searches!
Thinking about it more, I think the equilibrium state is when virtually all of the hydrogen is ionized. That's going to happen in a short time, just a few years. At that point the new nebula is going to look like any mature nebula- a sea of protons and a sea of free electrons. Yes, the mean recombination time is 10,000 years, but there are countless protons to recombine. What we see visually in an HII region is the light produced by only a tiny fraction of the total proton count recombining.
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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by Ann » Wed Feb 28, 2024 5:33 pm

Chris Peterson wrote: Wed Feb 28, 2024 4:10 pm
Christian G. wrote: Wed Feb 28, 2024 3:00 pm
Chris Peterson wrote: Wed Feb 28, 2024 1:39 pm

That's a tricky question. The ionization and recombination times are statistical values, like radioactive half-lives. So you need to think in terms of a distribution curve applied to a huge number of starting neutral atoms. What we would have to calculate is the time to equilibrium (the state that actual nebulas are in), and the shape of the curve ramping up to that point. I don't know (without doing more math than I feel like engaging in early in the morning) what that curve or time looks like, but I'm pretty sure we'd start detecting a glow fairly quickly.
Thanks for your answer. You definitely beat my google searches!
Thinking about it more, I think the equilibrium state is when virtually all of the hydrogen is ionized. That's going to happen in a short time, just a few years. At that point the new nebula is going to look like any mature nebula- a sea of protons and a sea of free electrons. Yes, the mean recombination time is 10,000 years, but there are countless protons to recombine. What we see visually in an HII region is the light produced by only a tiny fraction of the total proton count recombining.

That sounds good, Chris. I started thinking about how large a chunk 10,000 years is of an O-type star's main sequence life time, and it's actually not negligible. If we say that a typical main sequence life time of a hot O-type star of at least spectral class O5 is some 3 million years, then 10,000 years is about 0.3% of that star's main sequence life time. That's not negligible.

Let's say that a typical human life time is 80 years, or 960 months. 0.3% of 960 months is almost 3 months, and that is not a negligible part of a human life time. It's not the blink of an eye. So it would be strange if it took as long as 0.3% of a star's main sequence life time for hydrogen that has been ionized by that star to recombine.

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Re: APOD: Supernova Remnant Simeis 147 (2024 Feb 27)

Post by johnnydeep » Mon Mar 04, 2024 8:17 pm

Ann wrote: Wed Feb 28, 2024 8:17 am
johnnydeep wrote: Tue Feb 27, 2024 8:38 pm Ann wrote above:
Supernova remnants are highly ionized at their edges, where they typically glow blue-green. "Normal" emission nebulas are the other way round: they create OIII emission near their centers and less energetic forms of ionizations, such as Hα, further out.
Why is this, exactly?
As you know, Johnny, if you want an exact answer, you must ask Chris. But I'll have a go.

...

So the way I have understood it, the outer edges of expanding supernova remnants - and bear in mind that they are indeed expanding quite fast! - slam into the surrounding interstellar medium, and the "impact" produces just the amount of energy that ionizes oxygen and makes it glow blue-green.

As for emission nebulas, they expand, but they certainly don't expand very fast. They do push gas away from the hot stars and often make it pile up in a rim around the nebula, but they don't do it with enough force to ionize OIII. Instead, the amount of energy that ionizes oxygen is typically found in the relative vicinity of the hot main sequence or giant stars near the center of emission nebulas.

...

Ann
Thanks, Ann. So in brief summary, the green color of the outer edge of a supernova remnant results in about the same ionization of oxygen as the inner edge of an emission nebula that is typically close to a hot star.
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