UC Berkeley Press Release (June 9, 2009)
"The red supergiant star Betelgeuse, the bright reddish star in the constellation Orion, has steadily shrunk over the past 15 years, according to University of California, Berkeley, researchers.
"Long-term monitoring by UC Berkeley's Infrared Spatial Interferometer (ISI) on the top of Mt. Wilson in Southern California shows that Betelgeuse (bet' el juz), which is so big that in our solar system it would reach to the orbit of Jupiter, has shrunk in diameter by more than 15 percent since 1993.
"Since Betelgeuse's radius is about five astronomical units, or five times the radius of Earth's orbit, that means the star's radius has shrunk by a distance equal to the orbit of Venus...."
According to the UC Berkeley press release, Betelgeuse may continue to shrink - or it may not. The article explains why measurements made by Berkeley's Infrared Spatial Interferometer (ISI) are precise - and consistent - enough to tell scientists how the diameter of Betelgeuse has changed over the last 15 years. They show that "...over 15 years, it has decreased in size about 15 percent, changing smoothly, but faster as the years progressed...."
Astronomers will be wanting to keep an eye on Betelgeuse. As UC Berkeley's professor emeritus of physics, Charles Townes, put it: "...'Whenever you look at things with more precision, you are going to find some surprises and uncover very fundamental and important new things'...."
If "Charles Townes" sounds familiar, it should. He won the 1964 Nobel Prize in Physics for inventing the laser. And the maser: a laser that emits microwaves.
The press release also tells that Betelgeuse is farther away than the textbooks said when I was growing up. "...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...."
The UC Berkeley press release is a good source for information about the latest measurements of Betelgeuse - with more detail than you'll generally find in the news.
- "Lemming Tracks: All Betelgeuse, All the Time"
(June 10, 2009)