Arcturus is the brightest star in the northern celestial hemisphere. (The first three stars on this list are actually in the southern celestial sphere, though seasonally they are visible from the northern hemisphere of Earth).

Known as the Bear Watcher, Arcturus follows Ursa Major, the Great Bear, around the north celestial pole. The name itself derives from the Greek word arktos, meaning bear.

Arcturus is an orange giant, twice as massive and 215 times as bright as the Sun. It takes 37 years for the light of Arcturus to reach us, so when we gaze upon it, we are seeing the star as it looked 37 years ago. It glows at magnitude -0.04 in our night sky.

A variable star, Arcturus is in the last stages of life.

During its internal struggle between gravity and pressure, Arcturus has swelled to 25 times the Sun's diameter.

Eventually the outer envelope of Arcturus will peel away as a planetary nebula, similar to the famed Ring Nebula (M57) in Lyra. The star left behind will be a white dwarf.

Arcturus is the alpha (meaning brightest) star of the springtime constellation Bootes, the Herdsman. You can find it by using the Big Dipper as your celestial guidepost. Follow the arc of the handle until you come to a bright orange star. This is Arcturus, forming the point of a pattern of stars resembling a kite.

In the spring, if you keep following the arc, you'll encounter another bright star, Spica. (Keep it straight by remembering the phrase: "Arc to Arcturus, speed on to Spica.")

In the 1930s, astronomers were busy measuring the distance to nearby stars and determined—incorrectly, it turned out—that Arcturus was 40 light-years from Earth. During the 1933 World's Fair in Chicago, the light from Arcturus was collected with new photocell technology and used to activate a series of switches. Light believed to have originated at the time of the previous Chicago World's Fair 40 years earlier was used to illuminate and officially open the fair in 1933.

The science of astronomy progresses, and we now know that Arcturus is only 37 light-years away.