Arcturus, the fourth-brightest star in Earth's night sky, is about 20 times larger than the Sun, and it produces about a hundred times as much energy. But Arcturus is nearing the end of its life. In astronomical parlance, Arcturus has moved off the main sequence and entered the "giant" phase of its life. At a distance of about 35 light-years, it's closer to us than any other stellar giant.

Astronomers used light from Arcturus to help trip a switch that opened the 1933 World's Fair in Chicago.