APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

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APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby APOD Robot » Sun Jul 24, 2016 4:06 am

Image M2-9: Wings of a Butterfly Nebula

Explanation: Are stars better appreciated for their art after they die? Actually, stars usually create their most artistic displays as they die. In the case of low-mass stars like our Sun and M2-9 pictured above, the stars transform themselves from normal stars to white dwarfs by casting off their outer gaseous envelopes. The expended gas frequently forms an impressive display called a planetary nebula that fades gradually over thousands of years. M2-9, a butterfly planetary nebula 2100 light-years away shown in representative colors, has wings that tell a strange but incomplete tale. In the center, two stars orbit inside a gaseous disk 10 times the orbit of Pluto. The expelled envelope of the dying star breaks out from the disk creating the bipolar appearance. Much remains unknown about the physical processes that cause planetary nebulae.

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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby heehaw » Sun Jul 24, 2016 9:02 am

Note the incredible, detailed, symmetry of the two sides. I assume the two sides are the ejecta from the two rotation poles. It seems to me that the fact that the details are so exactly similar means that definable specific processes are at work: not random chance; so that if we had enough understanding we should be able to use theory to predict this outcome from circumstances at the star; or rather, deduce circumstances at the star from the observed results. How's that for a challenge to the theorists? Have at it, boys and girls!

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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Ann » Sun Jul 24, 2016 9:28 am

Solar corona. Photo: Miloslav Druckmuller (Brno University of Technology),
Peter Aniol, Vojtech Rusin. Larger size is here.
Spherical planetary nebula Abell39. Photo: Adam Block.

















I am obviously very, very much a non-expert when it comes to planetary nebulas. But I want to point out that even the Sun, middle-aged and almost perfectly spherical as it is, nevertheless looks bipolar when you consider its corona.

Perhaps the Sun, a single star, will eventually turn into a spherical planetary nebula. But I wouldn't be altogether surprised if it has some bipolarity up its sleeve.

Not that we ever will know.

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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Sun Jul 24, 2016 1:40 pm

Ann wrote:
Spherical planetary nebula Abell39. Photo: Adam Block.


I am obviously very, very much a non-expert when it comes to planetary nebulas. But I want to point out that even the Sun, middle-aged and almost perfectly spherical as it is, nevertheless looks bipolar when you consider its corona.

Perhaps the Sun, a single star, will eventually turn into a spherical planetary nebula. But I wouldn't be altogether surprised if it has some bipolarity up its sleeve.

Are you sure that's even a spherical nebula? After all, the very bipolar nebula in today's APOD might look exactly like that viewed from end-on. It's a challenge to figure out the true shape of many of these objects given the bias of our point-of-view.

Not that we ever will know.

That's a very pessimistic view. We might know with very high confidence.
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Guest » Sun Jul 24, 2016 2:14 pm

Chris Peterson wrote:
Ann wrote:
Spherical planetary nebula Abell39. Photo: Adam Block.


I am obviously very, very much a non-expert when it comes to planetary nebulas. But I want to point out that even the Sun, middle-aged and almost perfectly spherical as it is, nevertheless looks bipolar when you consider its corona.

Perhaps the Sun, a single star, will eventually turn into a spherical planetary nebula. But I wouldn't be altogether surprised if it has some bipolarity up its sleeve.

Are you sure that's even a spherical nebula? After all, the very bipolar nebula in today's APOD might look exactly like that viewed from end-on. It's a challenge to figure out the true shape of many of these objects given the bias of our point-of-view.


If we were looking down the rotational axis of this nebula, should we not see evidence of rotation in the image. I am assuming that material blown off the dying star retains its rotational moment in accordance with conservation of angular momentum. Also, if we looking down the axis, should we not see some elevated level of energy/particles (x-rays and other such outfall) being blasted towards us? I assume a slight wobble would be detectable in that case too. Wouldn't that make sense?

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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Sun Jul 24, 2016 3:17 pm

Guest wrote:
Chris Peterson wrote:Are you sure that's even a spherical nebula? After all, the very bipolar nebula in today's APOD might look exactly like that viewed from end-on. It's a challenge to figure out the true shape of many of these objects given the bias of our point-of-view.

If we were looking down the rotational axis of this nebula, should we not see evidence of rotation in the image.

What would you expect that to look like? How would we detect it?

I am assuming that material blown off the dying star retains its rotational moment in accordance with conservation of angular momentum.

Any material blown away is going to be traveling in an orbit around the center of mass of the nebula (basically, the parent star). If it was ejected at low speed it will be in a closed (elliptical) orbit. Anything ejected at greater than escape velocity (most of the material, probably) will be in an open (hyperbolic) orbit that is probably close to a straight line.

Also, if we looking down the axis, should we not see some elevated level of energy/particles (x-rays and other such outfall) being blasted towards us?

Why? The processes that produce planetary nebulas aren't particularly energetic. This is just a star with a little debris around it. We don't see stuff being blasted at us from the poles of other stars. These nebulas don't come from supernovas.

I assume a slight wobble would be detectable in that case too. Wouldn't that make sense?

I'm not sure why we'd necessarily see wobble, but if present, again, how would we detect that?
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Ann » Sun Jul 24, 2016 5:30 pm

Chris Peterson wrote:Are you sure that's even a spherical nebula?


Heck no. :wink:

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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby starsurfer » Sun Jul 24, 2016 5:40 pm

Chris Peterson wrote:Why? The processes that produce planetary nebulas aren't particularly energetic. This is just a star with a little debris around it. We don't see stuff being blasted at us from the poles of other stars. These nebulas don't come from supernovas.

Well some planetary nebulae do have bipolar jets, for once I won't include a link. I like Judy's remix of this, like she spilt some tropical juice on the original. :D :lol2:

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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Sun Jul 24, 2016 7:04 pm

starsurfer wrote:
Chris Peterson wrote:Why? The processes that produce planetary nebulas aren't particularly energetic. This is just a star with a little debris around it. We don't see stuff being blasted at us from the poles of other stars. These nebulas don't come from supernovas.

Well some planetary nebulae do have bipolar jets, for once I won't include a link. I like Judy's remix of this, like she spilt some tropical juice on the original. :D :lol2:

I'm not sure that "jets" is the right word, however. Many planetary nebulas show bipolar structure, suggesting that material was ejected faster along the rotational or magnetic poles. But do you know of any planetary nebulas that show anything other than low energy emissions (optical and longer), and that only from the surrounding shell? Do you know of any planetary nebulas that show anything at all coming from the star?
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby geckzilla » Sun Jul 24, 2016 9:40 pm

I do think it is highly likely that Abell 39 is a sphere or close to spherical shell. It is always possible that it's just a line of sight trick and that it could be some other shape, but it is also probably just fine to assume it's a spherical shell (shell is important. It would appear different if it was a "solid" sphere) without any compelling reason to think otherwise.

The collimated outflows of M2-9 present a more complex mystery to me. I do not know how it happens, but my own home baked hypothesis is that the star is emitting some kind of very light, fluffy material and that it becomes shaped by some denser rings of dust around the nucleus, closer to the star. Why dust? These young planetary nebulas often glow very brightly at 22 and 12 microns and this one is no exception. They are eye-catching in the WISE dataset, appearing in a 4 color WISE palette as intensely bright yellow stars. At the near-vacuum density levels and scale in space I am guessing that an area of dust performs more or less like some kind of solid compared to the even less dense gas flowing out from the star.

(Emphasis on the home-baked. Really. I'm not at all sure about it at all and it's certainly not something I have ever seen an actual astrophysicist mention.)
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Sun Jul 24, 2016 10:52 pm

geckzilla wrote:I do think it is highly likely that Abell 39 is a sphere or close to spherical shell.

So do I. I wasn't strongly suggesting otherwise, just pointing to the difficulty we have comparing one planetary to the next given the very real problem that our POV introduces.
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby starsurfer » Mon Jul 25, 2016 11:21 am

Chris Peterson wrote:Do you know of any planetary nebulas that show anything at all coming from the star?

Jets in planetary nebulae usually arise from an accretion disk around the central star. Also some planetary nebulae are known to have OIII blobs at the outer edges visible in deep images, so I guess these might be high excitation?

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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Mon Jul 25, 2016 2:22 pm

starsurfer wrote:
Chris Peterson wrote:Do you know of any planetary nebulas that show anything at all coming from the star?

Jets in planetary nebulae usually arise from an accretion disk around the central star. Also some planetary nebulae are known to have OIII blobs at the outer edges visible in deep images, so I guess these might be high excitation?

Well, it's a big universe and there's a lot of stuff out there, but are there planetary nebulas where their central stars have accretion discs? I can't think of any, and it isn't clear to me how that could even happen. Planetary nebulas are just the glow of ejected gas from late-state, lower mass stars which are hot enough to ionize that gas. Isotropically hot, no stellar structure, no stellar jets, just 30,000 K blackbodies.
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Ann » Sat Jul 30, 2016 6:27 am

Chris Peterson wrote:
starsurfer wrote:
Chris Peterson wrote:Do you know of any planetary nebulas that show anything at all coming from the star?

Jets in planetary nebulae usually arise from an accretion disk around the central star. Also some planetary nebulae are known to have OIII blobs at the outer edges visible in deep images, so I guess these might be high excitation?

Well, it's a big universe and there's a lot of stuff out there, but are there planetary nebulas where their central stars have accretion discs? I can't think of any, and it isn't clear to me how that could even happen. Planetary nebulas are just the glow of ejected gas from late-state, lower mass stars which are hot enough to ionize that gas. Isotropically hot, no stellar structure, no stellar jets, just 30,000 K blackbodies.


HEIC/ESO has just reported about a white dwarf star with a jet.

Are these "fully developed" white dwarf stars different from the central stars of planetary nebulas? Or is it true after all that the central stars of planetary nebulas can have jets?

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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Sat Jul 30, 2016 2:19 pm

Ann wrote:
Chris Peterson wrote:
starsurfer wrote:Jets in planetary nebulae usually arise from an accretion disk around the central star. Also some planetary nebulae are known to have OIII blobs at the outer edges visible in deep images, so I guess these might be high excitation?

Well, it's a big universe and there's a lot of stuff out there, but are there planetary nebulas where their central stars have accretion discs? I can't think of any, and it isn't clear to me how that could even happen. Planetary nebulas are just the glow of ejected gas from late-state, lower mass stars which are hot enough to ionize that gas. Isotropically hot, no stellar structure, no stellar jets, just 30,000 K blackbodies.


HEIC/ESO has just reported about a white dwarf star with a jet.

Are these "fully developed" white dwarf stars different from the central stars of planetary nebulas? Or is it true after all that the central stars of planetary nebulas can have jets?

To be clear, I'm not arguing that such stars can't have jets, only that I'm not familiar with any PNs where the central star (or stars if binary) actually do have them. The formation process for PNs seems rather gentle, and has the property (apparently) of clearing the region immediately around the star of material. That means that you don't have anything to accrete, and that means you're not going to have jets.

In a binary system, one of the stars can provide material to the other, which is what we have in the report above. Whether there are examples of such stars at the center of PNs, however, I don't know.
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby geckzilla » Sat Jul 30, 2016 8:03 pm

There are features that some planetary nebulas have known as FLIERs that might be related to some kind of short-lived jet-like action.
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby neufer » Sat Jul 30, 2016 10:12 pm

geckzilla wrote:
There are features that some planetary nebulas have known as FLIERs
that might be related to some kind of short-lived jet-like action.

https://en.wikipedia.org/wiki/NGC_6826 wrote:
<<NGC 6826 (also known as Caldwell 15) is a planetary nebula located in the constellation Cygnus. It is commonly referred to as the "blinking planetary", although many other nebulae exhibit such "blinking". When viewed through a small telescope, the brightness of the central star overwhelms the eye when viewed directly, obscuring the surrounding nebula. However, it can be viewed well using averted vision, which causes it to "blink" in and out of view as the observer's eye wanders.

A distinctive feature of this nebula are the two bright patches on either side, which are known as Fast Low-Ionization Emission Regions, or FLIERS. They appear to be relatively young, moving outwards at supersonic speeds, near the symmetry axis. Their outflow speeds are significantly higher than the nebulae in which they are embedded, and their ionizations are much lower. FLIERs' high speeds suggest ages much younger than their parent nebulae, and their low ionizations indicate that the ultraviolet radiation that ionizes the gas around them does not penetrate into the FLIERs.>>
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Sun Jul 31, 2016 3:57 am

neufer wrote:
geckzilla wrote:There are features that some planetary nebulas have known as FLIERs
that might be related to some kind of short-lived jet-like action.


I would not, however, remotely consider FLIERs to be jets of some sort. They're merely residual structure from the process that ejected the gaseous shell. Jets are active phenomena.
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby neufer » Sun Jul 31, 2016 9:52 am

Chris Peterson wrote:
neufer wrote:
geckzilla wrote:
There are features that some planetary nebulas have known as FLIERs
that might be related to some kind of short-lived jet-like action.

https://en.wikipedia.org/wiki/NGC_6826 wrote:
<<Their outflow speeds are significantly higher than the nebulae in which they are embedded, and their ionizations are much lower. FLIERs' high speeds suggest ages much younger than their parent nebulae, and their low ionizations indicate that the ultraviolet radiation that ionizes the gas around them does not penetrate into the FLIERs.>>
I would not, however, remotely consider FLIERs to be jets of some sort. They're merely residual structure from the process that ejected the gaseous shell. Jets are active phenomena.

You have no problem with a white dwarf producing active jets: viewtopic.php?f=31&t=36201
or Herbig–Haro (HH) active jets: http://apod.nasa.gov/apod/ap151218.html

...but a Planetary Nebula Nucleus (PNN) morphing/collapsing into a white dwarf
(or a Planetary Nebula Nucleus (PNN) companion white dwarf): viewtopic.php?f=31&t=36201#p260405

...cannot "remotely" produce active jets :?:
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Sun Jul 31, 2016 2:05 pm

neufer wrote:
Chris Peterson wrote:I would not, however, remotely consider FLIERs to be jets of some sort. They're merely residual structure from the process that ejected the gaseous shell. Jets are active phenomena.

You have no problem with a white dwarf producing active jets: viewtopic.php?f=31&t=36201
or Herbig–Haro (HH) active jets: http://apod.nasa.gov/apod/ap151218.html

...but a Planetary Nebula Nucleus (PNN) morphing/collapsing into a white dwarf
(or a Planetary Nebula Nucleus (PNN) companion white dwarf): viewtopic.php?f=31&t=36201#p260405

...cannot "remotely" produce active jets :?:

I didn't say that at all. What I said is that FLIERs aren't jets.
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby neufer » Sun Jul 31, 2016 2:40 pm

Chris Peterson wrote:
What I said is that FLIERs aren't jets.

You said that FLIERs aren't jets...because..."jets are active phenomena."

How do you know that FLIERs aren't "active phenomena"
(; e.g., the interaction of polar jets with planetary nebula) :?:
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Sun Jul 31, 2016 3:28 pm

neufer wrote:
Chris Peterson wrote:
What I said is that FLIERs aren't jets.

You said that FLIERs aren't jets...because..."jets are active phenomena."

How do you know that FLIERs aren't "active phenomena"
(; e.g., the interaction of polar jets with planetary nebula) :?:

I don't see any evidence of that, and the descriptions of FLIERs that are presented in the literature don't seem to suggest that they are anything but material produced very early in the gas shell ejection process. Have you seen something that argues otherwise?
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby neufer » Sun Jul 31, 2016 3:42 pm

Chris Peterson wrote:
neufer wrote:
Chris Peterson wrote:
What I said is that FLIERs aren't jets.

You said that FLIERs aren't jets...because..."jets are active phenomena."

How do you know that FLIERs aren't "active phenomena"
(; e.g., the interaction of polar jets with planetary nebula) :?:

I don't see any evidence of that, and the descriptions of FLIERs that are presented in the literature don't seem to suggest that they are anything but material produced very early in the gas shell ejection process. Have you seen something that argues otherwise?
https://en.wikipedia.org/wiki/Fast_Low- ... ion_Region wrote:
<<A Fast Low-Ionization Emission Region, or FLIER, is a volume of gas with low ionization, moving at supersonic speeds, near the symmetry axis of many planetary nebulae. Their outflow speeds are significantly higher than the nebulae in which they are embedded, and their ionizations are much lower. FLIERs' high speeds suggest ages much younger than their parent nebulae, and their low ionizations indicate that the ultraviolet radiation that ionizes the gas around them does not penetrate into the FLIERs.>>
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby Chris Peterson » Sun Jul 31, 2016 3:58 pm

neufer wrote:
Chris Peterson wrote:
neufer wrote:You said that FLIERs aren't jets...because..."jets are active phenomena."

How do you know that FLIERs aren't "active phenomena"
(; e.g., the interaction of polar jets with planetary nebula) :?:

I don't see any evidence of that, and the descriptions of FLIERs that are presented in the literature don't seem to suggest that they are anything but material produced very early in the gas shell ejection process. Have you seen something that argues otherwise?
https://en.wikipedia.org/wiki/Fast_Low- ... ion_Region wrote:
<<A Fast Low-Ionization Emission Region, or FLIER, is a volume of gas with low ionization, moving at supersonic speeds, near the symmetry axis of many planetary nebulae. Their outflow speeds are significantly higher than the nebulae in which they are embedded, and their ionizations are much lower. FLIERs' high speeds suggest ages much younger than their parent nebulae, and their low ionizations indicate that the ultraviolet radiation that ionizes the gas around them does not penetrate into the FLIERs.>>

Yes. So what in this makes you think they are the product of active jets? That's not my interpretation.
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Re: APOD: M2-9: Wings of a Butterfly Nebula (2016 Jul 24)

Postby neufer » Sun Jul 31, 2016 4:42 pm

Chris Peterson wrote:
neufer wrote:
Chris Peterson wrote:
I don't see any evidence of that, and the descriptions of FLIERs that are presented in the literature don't seem to suggest that they are anything but material produced very early in the gas shell ejection process. Have you seen something that argues otherwise?
https://en.wikipedia.org/wiki/Fast_Low- ... ion_Region wrote:
<<A Fast Low-Ionization Emission Region, or FLIER, is a volume of gas with low ionization, moving at supersonic speeds, near the symmetry axis of many planetary nebulae. Their outflow speeds are significantly higher than the nebulae in which they are embedded, and their ionizations are much lower. FLIERs' high speeds suggest ages much younger than their parent nebulae, and their low ionizations indicate that the ultraviolet radiation that ionizes the gas around them does not penetrate into the FLIERs.>>
Yes. So what in this makes you think they are the product of active jets? That's not my interpretation.

Well...it certainly doesn't just involve "material produced very early in the gas shell ejection process."

And there seems to be no reason to believe:

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