Dancing David
Penultimate Amazing
I too am educated by these threads.
Tell me, Michael: in all your careful image analysis, did you ever figure out what this bit I circled in blue was?
Why, it's the same stuff that you claim is coming from below the photosphere. Except it's deeper. Which means it's below your iron surface. Maybe your iron surface is transparent, or maybe there's a hole in your shell.
Why, it's the same stuff that you claim is coming from below the photosphere. Except it's deeper.
It's not deeper. Its facing you nand on a different area of the "surface". You're seeing down about 4800 km there too, it's just at a different point of the sphere and a different angle.
...and very pretty pictures they are. The latests SDO videos are amazing.
I'm just a lurker. Should this thread be dying - and that seems the direction its headed - I'd like to thank everyone for some very informative posts. Thanks Gee M, RC, Ben, Sol I, et al. Your posts got me thinking about image processing and the mechanisms of solar opacity. For all its Sound and Fury this was a good read.
Re limb darkening and brightening (this post is for lurkers)
As you might expect, the observed limb darkening of the Sun - in the 'optical' or 'visual' wavebands - was noticed a very long time ago, and has been studied, scientifically, for many centuries.
It is, of course, quite relevant to solar models, and provides important constraints on them, and did so especially before the time of space-based observations, helioseismology, etc. Unless and until it changes, Wikipedia provides a good, if brief, summary.
What most people - even many amateur astronomers - probably don't know is that limb darkening has been studied on stars other than the Sun, and for many decades before direct images of such stars were made (e.g. with the Hubble, of Betelgeuse).
The oldest technique is careful analysis of the light curves of eclipsing binaries - the exact shapes of the two eclipses encodes information on the limb darkening of each star, and detailed modelling can reveal the limb darkening.
Other techniques used include speckle interferometry (the image distortions produced by the Earth's atmosphere can, to some extent, be deconvolved to produce diffraction-limited data on stars, especially binaries), lunar occultations (making use of diffraction effects), various interferometers (the intensity interferometry of Hanbury-Brown is particularly interesting; today it's probably best known from the ESO's VLTs, and with the CHARA facility at Palomar), and gravitational microlensing.
Today, we are blessed with lots of free stuff, which incorporates the work of decades of PhD or MSc level effort; for example astronomycenter.org's Eclipsing Binaries ("This website provides both basic and advanced information on: simple models for computing light curves, a power point presentation on binary stars, student exercises, modeling close binary stars, and the shape of a rotating star. It also contains a free download of StarLight Pro which is software that produces animated views of eclipsing binary stars and calculates synthetic lightcurves. The effects of limb darkening, temperature, inclination, stellar size, mass ratio, and star shape are included.")
Needless to say, mainstream models of main sequence stars do not include photospheres which are essentially transparent over lengths of tens of thousands of km, in the EUV, VUV, UV, optical, or NIR wavebands. Why? Well, see if you can work out the answer for yourself!![]()
I'm hoping Michael will at least provide me with the plasma parameters and answer ben's question before he leaves, if that's where he's headed.
The thing is, Michael, suppose you're right and the sun has a solid iron surface, and that's what we're seeing in those VUV images. All the stuff we've been discussing - opacity, the trigonometry and temperature variations that lead to limb brightening/darkening - all that stuff is absolutely essential to extracting correct predictions from the iron sun model for what the SDO images should look like. You can't ignore those things in the standard model, and you can't ignore them in yours either.
That's a good thing - because suppose you could predict something for SDO that the standard model doesn't, and it actually gets observed. That would be pretty exciting, right?
I've learned a lot too,unlike Michael,poor bugger.
The energy state of the photosphere in the standard model is such that *NO* iron lines should extend even a *SINGLE* pixel into that composite image.
FYI sol, it looks to me from the SDO images that something in the photosphere interferes with FE 18. That one particular iron ion wavelength seems to be "blurrier" than the rest of the iron ion wavelengths to my eye. Any hint on what that might relate to in terms of elements? It looks to be related to an elemental valence shell configuration of something in the atmosphere rather than the energy state of neon.
Re limb darkening and brightening (this post is for lurkers)
As you might expect, the observed limb darkening of the Sun - in the 'optical' or 'visual' wavebands - was noticed a very long time ago, and has been studied, scientifically, for many centuries.
It is, of course, quite relevant to solar models, and provides important constraints on them, and did so especially before the time of space-based observations, helioseismology, etc. Unless and until it changes, Wikipedia provides a good, if brief, summary.
Optical depth is a very easy concept to grasp and to visualize, given that the image is a 2D representation of a 3D sphere. It doesn't even require any math skills.When we look near the edge of a star, we cannot "see" to the same depth as when we look at the center because the line of sight must travel at an oblique angle through the stellar gas when looking near the limb.
0) The telescope hasn't been calibrated yet.
a) Link to a specific image, please. I presume you mean "images taken with the AIA 94A filter". It's called Fe XVIII, not "FE 18"
b) With the exception of Rayleigh scattering, "interference" does not cause "blurriness".
And the second paragraph is quite relevant to Michael's delusion:
Birkeland's model is the *ONLY* solar model I'm aware of that "predicted" that the iron lines start under the surface of the photosphere at about 4800KM.
Michael, that image is not a cross-section of the sun. You aren't seeing below the surface when you look at the limb, you're seeing the surface at a steep angle. It's HARDER to see deep by looking at the limb than by looking at the center, not easier.
If they are based on image analysis by you?Pick one of the three predictions on my list and tell me which one would change your mind if I'm right?