Spotlight on Betelgeuse - Hubble Space Telescope's Faint Object Camera images red supergiant Betelgeuse - Brief Article

Science News, Jan 27, 1996 by Ron Cowen

Stars in the night sky-at least bright, nearby ones-need no longer appear as fuzzy points of lights in a heavenly picture. Taking advantage of the superior optics of the repaired Hubble Space Telescope, astronomers have for the first time directly imaged the face of a star other than our sun. Previous attempts to image stars have required intricate manipulation of multiple exposures.

Researchers used Hubble's Faint Object Camera to zero in on the red supergiant Betelgeuse, a swollen star whose brightness and girth-1,000 times the diameter of the sun-have made it a favorite target for telescopes on the ground. The ultraviolet image taken with Hubble highlights the extended atmosphere of Betelgeuse and reveals a single large hot spot in the star's southwest quadrant. The spot has a diameter about 10 times that of Earth and a temperature of roughly 7,000 kelvins, 2,000 kelvins higher than its surroundings.

In addition, there are smaller hot spots that speckle the sun "like German measles," says codiscoverer Andrea K. Dupree of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

She and Ronald L. Gilliland of the Space Telescope Science Institute in Baltimore suggest two explanations for the hot spot on Betelgeuse. As in a bubbling cauldron, pulsations of the star may have carried hot gas to the surface and caused hot spots to appear and vanish. Alternatively, energetic magnetic fields within the star may have generated the heat that produced the spot. Images taken over the next few years to show the spot's motion may help determine the correct explanation.