StarDate 7/9/2014: A Glittering Test Subject In The Summer Sky
FROM THE UNIVERSITY OF TEXAS McDONALD OBSERVATORY, AS HEARD ON KCBS RADIO WEEKDAYS @ 9:52 A.M., 7:35 P.M. & 2:52 A.M.
STARDATE 7/9/2014: Over the decades, when astronomers wanted a subject for testing new techniques for studying the stars, they frequently turned to Vega, the brightest star of Lyra, the harp. It’s one of the brightest stars in the night sky, it shines pure white, and it climbs high overhead as seen from most of the northern hemisphere, making it an excellent target.
In 1850, Vega became the first star other than the Sun to have its picture taken. In 1872, it became the first star to have its spectrum photographed — a development that allowed astronomers to study the chemical composition of stars in detail. And it was also one of the first stars with an accurate measurement of its distance.
More recently, Vega helped astronomers calibrate their observations of other stars. Under the stellar brightness scale, in which a lower number indicates a brighter star, Vega shines at “magnitude zero.” Astronomers could accurately measure the brightness of other stars by comparing them to Vega — a bright and familiar target in the summer sky.
Right now, Vega is high in the east at nightfall and crowns the sky around midnight. Deneb, the tail of Cygnus, the swan, is to the lower left of Vega as the sky gets dark. And Altair, the brightest star of Aquila, the eagle, is a little farther to the lower right of Vega. These three stars form the bright but wide-spread Summer Triangle, which remains in view not only in summer but all the way through autumn as well.