Giant Star in Sky Shrinking

Written by The Night Sky Guy on June 9, 2009 – 4:16 pm -

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 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. 

Hubbles View of Betelgeuses disk

Hubble's View of Betelgeuse's disk



Despite Betelgeuse’s diminished size, astronomers pointed out that its visible brightness, or magnitude, has shown no significant dimming over the past 15 years.

“But we do not know why the star is shrinking,” one of the researchers said. “Considering all that we know about galaxies and the distant universe,there are still lots of things we don’t know about stars, including what happens as red giants near the ends of their lives.”

Courtesy of 214th Meeting of the American Astronomical Society in Pasedena, California

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