In several articles, youtube clips and
the largest online astronomy textbook is stated that the star has a large envelope of gas and dust around it.
Quote:
Subsequent studies have reported an angular diameter (apparent size) ranging from 0.042 to 0.056 arcseconds, with the differences ascribed to the non-sphericity, limb darkening, pulsations, and varying appearance at different wavelengths. It is also surrounded by a complex, asymmetric envelope roughly 250 times the size of the star, caused by mass loss from the star itself. The angular diameter of Betelgeuse is only exceeded by R Doradus (and the Sun).
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And, as we know, dust scatters and takes all blue light out of the light of a light source. E.g. remember the Sun shining red through smoke or dust ? Is Betelgeuse not the same: a bluish white Rigel-like supergiant star shining through this envelope scattering the blue light and leaving a red appearence ? And other red supergiants like VY CMa, VV Cep, Antares ? Of which the first two are as large as Saturn's orbit and should be sooooo tenuous, that they cannot have a photosphere. Is it here a dust envelope of which we measure the dimensions ?
I do not stat this is true, it is just a possibility I think.
What are your ideas ?