Starship Asterisk*

jks wrote: ↑Sun Apr 25, 2021 7:00 am ... the date above the image should be 2021 April 25.

Ann wrote: ↑Sun Apr 25, 2021 9:04 am Today's APOD looks spectacular, of course.

For me, the problem is that the colors don't make the least bit of sense to me. I don't know what they represent. In particular, the "bits of blue" are totally unfathomable to me. And because of that, I feel "alienated" from the planetary nebula itself, and ultimately uninterested in the picture of it. ¯\_(ツ)_/¯

Ann

Chris Peterson wrote: ↑Sun Apr 25, 2021 1:51 pm

Ann wrote: ↑Sun Apr 25, 2021 9:04 am
For me, the problem is that the colors don't make the least bit of sense to me. I don't know what they represent. In particular, the "bits of blue" are totally unfathomable to me. ...

I don't think there is any blue in this image except for noise.

HubbleSite wrote:
Blue-violet: F502N (O III), Blue: F656N (Ha), Green: F658N (N II), and Red: F673N (S II)

bystander wrote: ↑Sun Apr 25, 2021 2:00 pm

Chris Peterson wrote: ↑Sun Apr 25, 2021 1:51 pm

Ann wrote: ↑Sun Apr 25, 2021 9:04 am
For me, the problem is that the colors don't make the least bit of sense to me. I don't know what they represent. In particular, the "bits of blue" are totally unfathomable to me. ...

I don't think there is any blue in this image except for noise.

Definitely not your standard mapping.

HubbleSite wrote:
Blue-violet: F502N (O III), Blue: F656N (Ha), Green: F658N (N II), and Red: F673N (S II)

bystander wrote: ↑Sun Apr 25, 2021 2:00 pm

Chris Peterson wrote: ↑Sun Apr 25, 2021 1:51 pm

Ann wrote: ↑Sun Apr 25, 2021 9:04 am
For me, the problem is that the colors don't make the least bit of sense to me. I don't know what they represent. In particular, the "bits of blue" are totally unfathomable to me. ...

I don't think there is any blue in this image except for noise.

Definitely not your standard mapping.

HubbleSite wrote:
Blue-violet: F502N (O III), Blue: F656N (Ha), Green: F658N (N II), and Red: F673N (S II)

johnnydeep wrote: ↑Sun Apr 25, 2021 3:12 pm Ok, reading some of the links, the progenitor star of Mz3 is said to be a Sun-like star near the end of its life. This would mean that it is now where our Sun will be in about 5 billion years. Wouldn't it appear to an observer at that time radically different than a "sun like" star? And so wouldn't the central star of Mz3 appear radically different to us now than our Sun does?

That is, what is it about the Mz3 nebula's progenitor star that we can measure now that makes us think it is/was a star similar to the sun? And for that matter, what does "similar" really mean in the context of stars? The only attributes I can think of are mass, spin, metallicity (elemental make-up), temperature, and age, with temperature likely solely dependent on the other attributes, and age not really relevant since I presume "sun like" would be a description that is independent of age.

Is it that "sun like" just means that a star is on the same "path" on the Hertzsprung–Russell diagram as the Sun is, and that no matter where a star is on a given H-R diagram path it will always follow that path throughout it's life time?

https://en.wikipedia.org/wiki/Mz_3 wrote:

Planetary Nebula Mz3: The Ant Nebula

---

The Butterfly Nebula, or PN M2-9, is a striking example of a bipolar planetary nebula. Bipolar planetary nebulae are formed when the central object is not a single star, but a binary system, Studies have shown that the nebula’s size increases with time, and measurements of this rate of increase suggest that the stellar outburst that formed the lobes occurred just 1200 years ago.

---

<<Mz 3 has several components with varying degrees of collimation. It also has an unusual spectrum. Together, these entitle it to the nickname of "The Chamber of Horrors" of planetary nebulae as given by Evans in 1959. Mz 3 is radially expanding at a rate of about 50 km/s and has its polar axis oriented at an angle of around 30° from the plane of the sky (Lopez & Meaburn 1983; Meaburn & Walsh 1985).

Mz 3 is sometimes compared to the more extensively studied Butterfly Nebula (M 2-9) , and it is quite likely that both have a similar evolutionary history. They both have point-like bright nuclei, are narrow-waisted bipolar nebulae, and share surprisingly similar spatially dependent spectra. Because of their similarity, their differences are noteworthy. Their greatest difference is probably in their near infrared emissions. Mz 3 has no trace of molecular hydrogen emission, whereas the M 2-9 has prominent H₂ emission lines in the near-IR. The lack of H₂ emissions from Mz 3 is unusual given the strong correlation between such emissions and bipolar structures of PN. Additionally, the polar lobes of Mz 3 are more mottled and rounded as compared to M 2-9. Finally, Mz 3 is not known to evidence temporal variability in its polar lobes as is found in M 2-9 (Doyle et al. 2000). (Smith 2003)

The Herschel Space Observatory has detected laser light emissions from the nebula -- specifically, hydrogen recombination line laser emissions. This confirms the presence of a white dwarf with a binary companion at the heart of the nebula.>>

neufer wrote: ↑Sun Apr 25, 2021 3:28 pm

https://en.wikipedia.org/wiki/Mz_3 wrote:

Planetary Nebula Mz3: The Ant Nebula

---

The Butterfly Nebula, or PN M2-9, is a striking example of a bipolar planetary nebula. Bipolar planetary nebulae are formed when the central object is not a single star, but a binary system, Studies have shown that the nebula’s size increases with time, and measurements of this rate of increase suggest that the stellar outburst that formed the lobes occurred just 1200 years ago.

---

<<Mz 3 has several components with varying degrees of collimation. It also has an unusual spectrum. Together, these entitle it to the nickname of "The Chamber of Horrors" of planetary nebulae as given by Evans in 1959. Mz 3 is radially expanding at a rate of about 50 km/s and has its polar axis oriented at an angle of around 30° from the plane of the sky (Lopez & Meaburn 1983; Meaburn & Walsh 1985).

Mz 3 is sometimes compared to the more extensively studied Butterfly Nebula (M 2-9) , and it is quite likely that both have a similar evolutionary history. They both have point-like bright nuclei, are narrow-waisted bipolar nebulae, and share surprisingly similar spatially dependent spectra. Because of their similarity, their differences are noteworthy. Their greatest difference is probably in their near infrared emissions. Mz 3 has no trace of molecular hydrogen emission, whereas the M 2-9 has prominent H₂ emission lines in the near-IR. The lack of H₂ emissions from Mz 3 is unusual given the strong correlation between such emissions and bipolar structures of PN. Additionally, the polar lobes of Mz 3 are more mottled and rounded as compared to M 2-9. Finally, Mz 3 is not known to evidence temporal variability in its polar lobes as is found in M 2-9 (Doyle et al. 2000). (Smith 2003)

The Herschel Space Observatory has detected laser light emissions from the nebula -- specifically, hydrogen recombination line laser emissions. This confirms the presence of a white dwarf with a binary companion at the heart of the nebula.>>

Ann wrote: ↑Sun Apr 25, 2021 3:32 pm Speak about weird colors. What are the blue bits doing in the Butterfly Nebula? And what do the other colors mean?

Chris Peterson wrote: ↑Sun Apr 25, 2021 3:44 pm

Ann wrote: ↑Sun Apr 25, 2021 3:32 pm Speak about weird colors. What are the blue bits doing in the Butterfly Nebula? And what do the other colors mean?

The blue channel is OIII (502 nm).
The green channel is wide V (575 nm center).
The red channel is SII (673 nm).

Converting that information into the meaning of colors, however, is non-trivial.

Ann wrote: ↑Mon Apr 26, 2021 12:04 am

Chris Peterson wrote: ↑Sun Apr 25, 2021 3:44 pm

Ann wrote: ↑Sun Apr 25, 2021 3:32 pm Speak about weird colors. What are the blue bits doing in the Butterfly Nebula? And what do the other colors mean?

The blue channel is OIII (502 nm).
The green channel is wide V (575 nm center).
The red channel is SII (673 nm).

Converting that information into the meaning of colors, however, is non-trivial.

Well, let's see. There's a lot of green stuff in the Hubble image of Minkowski's Butterfly. The green stuff is either OIII, or a mixture of OIII and some other more or less green stuff, or just the other green stuff that can't be identified. But the blue stuff is OIII.

We may note that there is apparently no H-alpha in Minkowski's Butterfly, but there is, on the other hand, relatively large amounts of SII.

I guess it was more important for whoever decided on the filters for the picture of Minkowski's Butterfly to make this nebula look like a cosmic opal than to give us a clear idea of what elements we are seeing in it.

Fission wrote: ↑Wed Apr 28, 2021 2:11 am I am confused by some of the nomenclature. The commentary refers to the central star as similar to the Sun. However, a planetary nebula is said to be an end of life event usually for a red giant star and the Sun is a young star Which is this - young or old?

Chris Peterson wrote: ↑Wed Apr 28, 2021 2:30 am

Fission wrote: ↑Wed Apr 28, 2021 2:11 am I am confused by some of the nomenclature. The commentary refers to the central star as similar to the Sun. However, a planetary nebula is said to be an end of life event usually for a red giant star and the Sun is a young star Which is this - young or old?

A red giant is a more evolved state of a star like the Sun. It's where the Sun will be in a few billion years.

johnnydeep wrote: ↑Wed Apr 28, 2021 3:28 pm

Chris Peterson wrote: ↑Wed Apr 28, 2021 2:30 am

Fission wrote: ↑Wed Apr 28, 2021 2:11 am I am confused by some of the nomenclature. The commentary refers to the central star as similar to the Sun. However, a planetary nebula is said to be an end of life event usually for a red giant star and the Sun is a young star Which is this - young or old?

A red giant is a more evolved state of a star like the Sun. It's where the Sun will be in a few billion years.

I'll echo what I asked above: so how do we know that this star is/was on the same path - though much further along - that the Sun is/will be?

Chris Peterson wrote: ↑Wed Apr 28, 2021 3:31 pm

johnnydeep wrote: ↑Wed Apr 28, 2021 3:28 pm

Chris Peterson wrote: ↑Wed Apr 28, 2021 2:30 am

A red giant is a more evolved state of a star like the Sun. It's where the Sun will be in a few billion years.

I'll echo what I asked above: so how do we know that this star is/was on the same path - though much further along - that the Sun is/will be?

All stars in a certain mass range will follow a similar path.

johnnydeep wrote: ↑Wed Apr 28, 2021 4:36 pm

Chris Peterson wrote: ↑Wed Apr 28, 2021 3:31 pm

johnnydeep wrote: ↑Wed Apr 28, 2021 3:28 pm

I'll echo what I asked above: so how do we know that this star is/was on the same path - though much further along - that the Sun is/will be?

All stars in a certain mass range will follow a similar path.

And how do we know that the mass of this star 5 billion years ago was similar to the Sun now? Is it only because the mass left over even after blowing off the planetary nebula is still close to the original (i.e., the mass of the nebula is a small percentage of the total)?

Chris Peterson wrote: ↑Wed Apr 28, 2021 4:47 pm

johnnydeep wrote: ↑Wed Apr 28, 2021 4:36 pm

Chris Peterson wrote: ↑Wed Apr 28, 2021 3:31 pm

All stars in a certain mass range will follow a similar path.

And how do we know that the mass of this star 5 billion years ago was similar to the Sun now? Is it only because the mass left over even after blowing off the planetary nebula is still close to the original (i.e., the mass of the nebula is a small percentage of the total)?

If it was much lower mass it wouldn't have had time to get to this stage yet. If it were much more, it wouldn't have ended as a white dwarf and a planetary nebula. Presumably the mass can also be refined from estimates of the mass of ejected material and the white dwarf, to the extent they can be determined.

johnnydeep wrote: ↑Wed Apr 28, 2021 6:34 pm

Chris Peterson wrote: ↑Wed Apr 28, 2021 4:47 pm

johnnydeep wrote: ↑Wed Apr 28, 2021 4:36 pm

And how do we know that the mass of this star 5 billion years ago was similar to the Sun now? Is it only because the mass left over even after blowing off the planetary nebula is still close to the original (i.e., the mass of the nebula is a small percentage of the total)?

If it was much lower mass it wouldn't have had time to get to this stage yet. If it were much more, it wouldn't have ended as a white dwarf and a planetary nebula. Presumably the mass can also be refined from estimates of the mass of ejected material and the white dwarf, to the extent they can be determined.

Ah, thanks.

Chris Peterson wrote: ↑Wed Apr 28, 2021 6:42 pm

johnnydeep wrote: ↑Wed Apr 28, 2021 6:34 pm

Chris Peterson wrote: ↑Wed Apr 28, 2021 4:47 pm

If it was much lower mass it wouldn't have had time to get to this stage yet. If it were much more, it wouldn't have ended as a white dwarf and a planetary nebula. Presumably the mass can also be refined from estimates of the mass of ejected material and the white dwarf, to the extent they can be determined.

Ah, thanks.

Without information to the contrary, I'd guess that the reference to being similar to the Sun was just a generic recognition that the white dwarf at the center of a planetary nebula can basically be described that way. Keep in mind that the system which produced this PN was almost certainly nothing like our own, since it most likely represents a binary pair, with an existing giant and the white dwarf.