As Orion crests across the southern skies, his bright stars demonstrate considerably differences in color. Compare, for example, the star Betelgeuse on the upper left, appearing an orangish color, while on the lower right, Rigel shines a piercing blue. The colors indicate the star’s outer temperature, with red much cooler than the very hot blue.

Orion boasts a fine collection of bright stars, including the bluish-white beacon to the lower right of his three belt stars. Rigel, meaning “left foot”, is classified as a blue supergiant, estimated to be 860 light years, and emitting approximately 200 thousand times more light than the Sun.

Today marks the anniversary of the discovery of Pluto. Clyde Tombaugh was examining pictures taken through the telescope at the Lowell Observatory in Arizona in January, 1930, over a period of days. One of the “stars” in the image moved while the stars remained in place, revealing the frozen world for the first time.