This month look for the star Arcturus, the lucida of the constellation of Bootes, the Herdsman. Arcturus is located 37 light years from earth. Therefore, if you were born in 1976, Arcturus is your birthday star this year. The word, Arcturus, means “Bear Guardian” and is a reference to its closeness to the Great Bear, or Ursa Major. As the constellation of the Big Bear wheels around the sky, the bright star Arcturus follows closely behind.  

The light of Arcturus opened the 1933 World’s Fair in Chicago. At that time, the best measurement of the distance to this star pegged it at 40 light years. Since the previous World’s Fair in Chicago occurred forty years earlier, the starlight seen from Arcturus at the opening of the 1933 fair had left the star during the last fair. To open the 1933 World’s Fair, a large telescope lens focused the Arcturian starlight on a photocell (a light-sensitive resistor). The electrical signal generated by the star’s light shining on the photocell was used to switch on the lights of the fair. 

Arcturus is a spectral type K star, meaning its cooler than our sun and produces less light per square foot of surface. Instead of being yellow like our sun (which is a G spectral type), Arcturus is a cooler orange. However, because of its larger diameter, Arcturus shines over 100 times more brightly than our sun. If its infrared radiation is included, then the star is over 200 times brighter than our sun. It would take 26 of our suns to span the diameter of Arcturus. If the star replaced the sun in our sky, it would cover an area of the sky two times larger than the palm of your outstretched hand. The surface of Arcturus would reach one-quarter of the way to the orbit of Mercury. Of course, the larger mass, diameter, and radiation from Arcturus would end all life on Earth with the possible exception of bacteria living far underground.  

To find Arcturus, follow the bend of the handle of the Big Dipper. An arc drawn from the end of the Dipper’s handle (actually the Large Bear’s tail) leads you to Arcturus. In June, Arcturus passes almost directly overhead.