Star of Joy

The star of joy, Arcturus, is a beacon of light.

Arcturus is the brightest star in the constellation Boötes. It is also the third brightest star in the night sky, after Sirius and Canopus. It is the second brightest star visible from northern latitudes and the brightest star in the northern celestial hemisphere.

An easy way to find Arcturus is to follow the arc of the handle of the Plough. By continuing in this path, one can find Spica —hence the maxim, "Arc to Arcturus"

Prehistoric Polynesian navigators knew Arcturus as Hokule'a, the "Star of Joy". Arcturus is the zenith star of the Hawaiian Islands. Using Hokule'a and other stars, the Polynesians launched their double-hulled canoes from Tahiti and the Marquesas Islands. Traveling east and north they eventually crossed the equator and reached the latitude at which Arcturus would appear directly overhead in the summer night sky. Knowing they had arrived at the exact latitude of the island chain, they sailed due west on the trade winds to landfall. If Hokule'a could be kept directly overhead, they landed on the southeastern shores of the Big Island of Hawaii. For a return trip to Tahiti the navigators could use Sirius, the zenith star of that island. Since 1976, the Polynesian Voyaging Society's Hokule'a has crossed the Pacific Ocean many times under navigators who have incorporated this wayfinding technique in their non-instrument navigation.

The name of the star derives from Ancient Greek Arktouros, and means "Guardian of the Bear". This is a reference to it being the brightest star in the constellation Boötes (of which it forms the left foot), which is next to the Greater and Lesser Bears, Ursa Major and Ursa Minor.

information from Wikipedia

diagram from www.earthsky.org

At the time of the 1933 Chicago world's fair, astronomers had been measuring distances to objects in the universe. They believed Arcturus to be 40 light years away. Which meant that the light that we saw when we looked up at Arcturus in the sky, had left the star 40 years ago. Well, guess when Chicago last had a world's fair? 40 years before in 1893. Somebody planning the fair must have been an astronomy buff! They decided to use that little astronomical tidbit to spice up the 1933 fair. While most people had a passing interest in such astronomical knowledge, it just didn't generate the kind of excitement needed to open a world's fair, so it was necessary to get creative.

Now comes the part about the photocell. Photocells absorb light and turn it into a primitive electrical energy, not much energy mind you, but enough to do something like turn on a small switch. Photocells were new and exciting technology back in 1933, and it was decided to demonstrate this new wonder by using it to turn on all the lights at the opening ceremony of the world's fair.

In the end what they did was point a telescope at the star Arcturus. The light from the telescope was aimed at a photocell. The photocell was connected to a small switch, which was, in turn, connected to other larger switches. When enough light from Arcturus (which had left the star 40 years before when the last world's fair was at Chicago in 1893) had gathered in the photocell, it tripped the switch that opened the 1933 world's fair. So now, as you can see, all the pieces fit together. People were impressed, the world's fair was a success.

You may not be quite as awed as the 1933 crowd, and you may be even less impressed when you find that they didn't have the distance quite right. While the actual distance is 36 light-years, you could argue it was close enough for the purpose. But it does give you something novel to think about if you go out and look at the night sky.

information from http://starryskies.com

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