With progressing nuclear fusion in the center of a star, brightness, size, and color also change. Astrophysicists can derive from such properties important information on age and mass of a star. Those stars with significantly more mass than our Sun are blue-white or red - the transition from red via yellow and orange is relative rapid for astronomical time-scales. Astrophysicists of Friedrich Schiller University Jena, Germany, together with colleagues of other subjects from the USA and Italy, have now been successful to detect and date such a color change in a bright star. With several historical sources, they found that Betelgeuse - the bright red giant star in the upper left of the constellation Orion - was yellow-orange some 2,000 years ago. ...
