APOD: The Extraordinary Spiral in LL Pegasi (2021 Nov 29)

Comments and questions about the APOD on the main view screen.
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Re: APOD: The Extraordinary Spiral in LL Pegasi (2021 Nov 29)

Post by alter-ego » Wed Dec 01, 2021 5:25 am

VictorBorun wrote:
Tue Nov 30, 2021 7:57 am
wiki says LL Pegasi is even farther away, 1,300 pc
I took the 1kpc at face value, on the basis of mass outflow velocity, and the 700 yr to 800 yr shell separation. With that said, I would tend to give the newer Wiki estimate more credence.
I wonder how far it is from the disk of Milky Way and what bright stars are main illuminators
The caption in Fig. 1 (the aforementioned paper) says the galactic plane is 650pc away.
It's a surprise for me to know how dense the soot around a carbon red giant is, to cover it and its companion so thick that the Milky Way (dominating the starry sky outside the galaxy disk) is brighter than the stars within the shells.
Yeah, it's dense, as indicated by Keck's and ALMA images, but still, it seems that the supposed blue companion should be noticeable. On the other hand, the spiral's one-sided illumination also looks convincingly like an external source. Considering the 3D aspects, maybe the scattered light is escaping at lower latitudes with much less escaping out the nebula's poles. Like Chris said, it is odd why spectra measurements haven't resolved this. Interesting it is.
Compare with an observer at Kuiper belt. There is our Sun, there are Sirius and Vega. The Milky Way is not dominating at all as a lamp for Pluto's hills.
Well, our solar system literally has no extinction relative to LL Pegasi. From Pluto, the Sun's brightness is not noticeably attenuated, it's magnitude is about -19, so clearly the Sun dominates over all other light sources. The Integrated Flux Neblua is an example of nebula structures illuminated by stars in the galactic plane. I don't have a sense though if conditions are comparable to the spiral nebula.
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Re: APOD: The Extraordinary Spiral in LL Pegasi (2021 Nov 29)

Post by VictorBorun » Wed Dec 01, 2021 12:21 pm

Astronymus wrote:
Tue Nov 30, 2021 7:31 pm
VictorBorun wrote:
Mon Nov 29, 2021 9:45 am
somehow the northern segments of the coils are compressed in relation to the other segments
LLPegasi_HubbleLodge_1926..png
First guess would be that's the direction of movement by the system. The cloud falls behind.
I'm taking my statement back.
With sub mm overlay we can see as many as 5 coils in all directions, and all the different steps we see are only for some of the coils.
If the binary system were moving it would not start and stop like this.
The trick with northern part of two or three coils has to be due to periods of soot wind at lower velocity.