shrinking Betelgeuse

On Thu, 11 Jun 09 12:52:33 GMT, Phillip Helbig wrote:
Townes has been using the same setup and has seen the star shrink by 15%
at a given wavelength.

Yes, but the star already shows variances of 30% apparent diameter at
different wavelengths. If the star is seen to be shrinking by 15% in
every wavelength, that woud be significant. The article states that
Townes operates at the wavelength of a calibrating laser, in the
mid-infrared. So, the article is based on one wavelength only.

So we have a choice of assumptions. If we assume that there are no
resonances or other internal process operating within Betelgeuse's
vapor-thin exosphere, which would cause the glow in that exosphere to
vary, then we deduce a huge physical contraction in the whole star.
On the other hand, if we assume no contraction, then we deduce that
there are resonances or other processes which cause variations in the
glow, like a neon lamp can glow faint or bright. And the gas in
Betelgeuse's "surface" is more attenuated than the gas in a neon lamp.

So I think a neon-lamp-like resonance in the surface of the star is
more likely than a massive contraction, in the absence of other data
beyond that of a single wavelength. That's all I've got.

Eric