Betelgeuse << BEE tuhl jooz >> , also called Alpha Orionis, is one of the brightest stars in the constellation Orion, the Hunter. Betelgeuse is one of the nearest examples of a red supergiant, a massive star that has nearly burned up all of its fuel. Betelgeuse has a deep red color because its surface temperature is low for a star—only half that of the sun. But Betelgeuse’s diameter is at least 600 times that of the sun. For this reason, the star gives off about 100,000 times as much light as does the sun. Betelgeuse is a star of the first magnitude, placing it among the brightest stars in Earth’s sky (see Magnitude ).
Some measurements have suggested that Betelgeuse lies about 495 light-years from Earth. One light-year equals about 5.88 trillion miles (9.46 trillion kilometers). Other measurements, conducted in the early 2000’s, suggest Betelgeuse may be 640 light-years from Earth. The extra distance would mean that Betelgeuse is actually about 30 percent brighter and larger.
Astronomers estimate Betelgeuse to have at least 15 times the sun’s mass (amount of matter). Stars of this size eventually explode in an event called a supernova . During supernova, Betelgeuse will appear millions of times brighter than it appears now, temporarily outshining even the moon.
In 2009, the American physicists Charles Townes and Edward Winslow announced that Betelgeuse is shrinking. Their announcement was based on a 15-year study of the star that showed a 15 percent decrease in the diameter of the star over that period. The two scientists carried out their observations using the Infrared Spatial Interferometer (ISI) on Mount Wilson in California (see Interferometer ).
Later in 2009, two teams, one led by the French astronomer Pierre Kervella of the Paris Observatory and the other led by Keiichi Ohnaka of the Max Planck Institute for Radio Astronomy in Bonn, Germany, imaged Betelgeuse in greater detail than ever before. Their combined observations revealed a cloud of gas surrounding Betelgeuse that, if it were in our solar system, would extend from the sun to Neptune. These observations reinforce astronomers’ belief that Betelgeuse is in the last stages of its life before becoming a supernova. Both teams performed their observations using the European Organisation for Astronomical Research in the Southern Hemisphere’s (ESO) Very Large Telescope (VLT) facility in Chile (see Very Large Telescope ).
The American physicist Albert Michelson originally measured the size of Betelgeuse in 1921. In 1985, it became the first star besides the sun to have its surface imaged.
