Stargazers: Arcturus demonstrates its ‘star’ power

Last week, I wrote in part about the star Arcturus, and I hope you got out to see its beautiful yellow-orange light. This week, you’ll learn what radio personality Paul Harvey might have called “the rest of the story.”

It was on a beautiful Chicago evening 85 years ago this week — May 27, 1933 — that crowds gathered at the fairground for a night they had awaited for many years.

Much as they do today, event organizers had engaged the services of a famous star to throw the switch and open the festivities. And as anticipation reached a peak, it was time.

At 9:15 p.m., the floodlights ignited, and the fairgrounds were bathed in light. The long-awaited Century of Progress Exposition was open.

I’m sure that many have heard of the Century of Progress Exposition; in fact, some of my readers may have even attended it as youngsters.

But what many don’t know is the rest of the story, for the star that threw the switch that night was not of the human variety, nor was it a famous animal celebrity of the day.

No, the star that opened the Exposition reached in from its perch 222 trillion miles above Chicago. Its name was Arcturus.

Arcturus is the fourth brightest star in our night sky and the brightest in the constellation Bootes, the herdsman. Look for its yellowish-orange glow this week as it hovers high in the eastern sky after dark. You can confirm its location easily by using the handle of the Big Dipper to “arc” your way toward it.

Gaze toward Arcturus and you will see a red giant star some 25 times larger and 180 times more powerful than our sun. It appears so bright in our sky because it is one of the stars nearest Earth.

Arcturus was one of the first stars ever to receive a proper name. In his classic book “Star Names and Their Meanings,” author Richard Hinckley Allen devotes several pages to the mythological references to this star. In ancient times, it was known as the “Watcher” or the “Guard­ian.”

Today we use a name that comes from the ancient Greek word “arktouros,” meaning “Bear Guard.”

Arcturus was also the first star ever to be seen in daylight with a telescope. That was in 1635, but today, we can do this rather easily, even with a modest backyard instrument, if we know exactly where to look.

But it was after dark on May 27, 1933, that all eyes in Chicago were on this star. Astronomers at the nearby Yerkes Observatory aimed its 40-inch refracting telescope toward Arcturus to capture its light and focus it onto photoelectric cells. They then transmitted the electrical current it generated to flip the switch that illuminated the Exposition.

So, of all the stars in all the heavens, why did Exposition officials choose Arcturus? Because the star was known to lie about 40 light-years from Earth, and the light that triggered the photo cells on that night would have left the star in 1893, the year of Chicago’s previous great world exposition.