Betelgeuse is shrinking

It has shrunk 15% since 1993. [Link]

Betelgeuse is so big that in our solar system it would reach to the orbit of Jupiter. Its radius is about five astronomical units, or five times the radius of Earth’s orbit. Its measured shrinkage means the star’s radius has shrunk by a distance equal to the orbit of Venus.

“To see this change is very striking,” said Charles Townes, a UC Berkeley professor emeritus of physics. “We will be watching it carefully over the next few years to see if it will keep contracting or will go back up in size.”

And this is amazing:

Betelgeuse was the first star ever to have its size measured, and even today is one of only a handful of stars that appears through the Hubble Space Telescope as a disk rather than a point of light. In 1921, Francis G. Pease and Albert Michelson used optical interferometry to estimate its diameter was equivalent to the orbit of Mars. Last year, new measurements of the distance to Betelgeuse raised it from 430 light-years to 640, which increased the star’s diameter from about 3.7 to about 5.5 AU.