Arcturus, a red giant, looks orange to the eye. It’s the brightest star on the northern half of Earth’s sky dome.
Arcturus’ constellation Bootes – the Herdsman – is sometimes pictured as guarding the Great Bear, or Ursa Major, which contains the Big Dipper asterism. We sometimes hear Arcturus called the Bear Guard.
One interesting story about Arcturus relates to the 1933 Century of Progress Exhibition in Chicago. Its promoters wanted a flashy way to open the show, so they decided to have the light from Arcturus pass through a telescope onto a photocell. The photocell in turn worked as the switch that turned on the main spotlights to open the exhibition. There had also been a World’s Fair in Chicago in 1893, 40 years before the 1933 show. At the time, astronomers thought that Arcturus was 40 light-years away. So they thought that light left Arcturus at the end of the 1893 fair and traveled for 40 years through space like an Olympic torch bearer, to open the 1933 show.