In article ,
(Eric Flesch) writes:

Interesting article, but there are clues that Betelgeuse is not
actually shrinking. The article states:

"Since the 1921 measurement, its size has been re-measured by many
different interferometer systems over a range of wavelengths where the
diameter measured varies by about 30 percent," Wishnow said. "At a
given wavelength, however, the star has not varied in size much beyond
the measurement uncertainties."

I think that refers to 1921--1991 or so, i.e. before Townes's
measurements. In other words, no shrinkage back then.

"The measurements cannot be compared anyway, because the star's size
depends on the wavelength of light used to measure it, Townes said.
This is because the tenuous gas in the outer regions of the star emits
light as well as absorbs it, which makes it difficult to determine the
edge of the star."

Right---one can't straightforwardly compare older measurements made at
different wavelengths.

The article then describes that Townes finds a way around this
problem, but with Betelgeuse now said to be shrinking by 15%, it is
apparent that Townes has not got the answer after all. I trust the
star more than the astronomer.

Townes has been using the same setup and has seen the star shrink by 15%
at a given wavelength.