Making a Cosmic Connection with Arcturus

You can't miss the twinkly, red-orange gleam of Arcturus at dusk in the western sky. Physically and culturally it's one of the most interesting stars in the sky. DSS2 / Aladin Sky Atlas

Look in the western sky as soon as it gets dark, and you'll see a single bright orange star. That's Arcturus, fourth brightest in the night sky. It shines at magnitude 0 and lies 36.7 light years from Earth. Twinkles of its light that enervate your retinas tonight began their journey in 1983 when the world's population was 4.7 billion (it's now 7.8 billion) and before there was an internet. 

Arcturus is the brightest star in Boötes the Herdsman. If you have any trouble finding it just follow the arc of the Dipper's handle. Stellarium

Arcturus is a red giant star about 25 times the size of the sun. If Arcturus took over our star's job at the center of our solar system it would span more than a dozen degrees, larger than the bowl of the Big Dipper. Although its surface temperature is a few thousand degrees cooler than the sun's it shines 113 times more brightly and would undoubtedly roast us alive.

Arcturus is moving rapidly across the sky relative to the solar system, the reason its motion is apparent in a relatively short time. Stellarium

Arcturus is also moving at the tremendous velocity of 75 miles a second (120 km/sec) perpendicular to our line of sight. As such it's one of a very few bright stars to show a noticeable shift in position in the sky since ancient times. A sharp-eyed skywatcher from Aristotle's day who stepped into a time machine and fast-forwarded to 2020 would easily note that the star had moved about 1.5° (3 moon diameters) to the southwest. 

87 years ago Arcturus became a famous star — in the Hollywood sense. In May 1933 the city of Chicago held its Century of Progress Exposition, also known as the Chicago World's Fair, to highlight the importance of science in American life. 40 years prior in 1893, the city had hosted its first big fair, the World's Columbian Exposition. 

Edwin Frost. National Academy of Sciences

Edwin Frost, retired director of the Yerkes Observatory in nearby Williams Bay, Wis., hatched a wonderful plan to symbolically — and cosmically — connect the two events using the star Arcturus. He proposed that astronomers focus the star's light onto a photocell and use the electric current generated to flip a switch that would turn on the lights to illuminate the fairgrounds at its opening. 

At the time it was thought that Arcturus was 40 light years from Earth, so the light that left the star 40 years prior in 1893 during the previous fair would arrive 40 years later just in time for current one. The timing was ideal in another way as visitors could look up and see the star high in the southern sky at nightfall. Could there be a more poetic use of starlight? 

Yerkes Observatory, home to the largest refracting telescope in the world, would participate as would telescopes at the University of Illinois (Urbana-Champaign), Harvard College Observatory and Allegheny Observatory (Pittsburgh) in case one or more locations were clouded over. On May 27, 1933, the evening of the big event, fair president, Rufus Dawes spoke to a crowd of more than 30,000 people assembled in the courtyard at the Hall of Science: 

The Hall of Science at the Chicago fairgrounds where the light of Arcturus came to Earth. Newberry Collection / Public Domain 

"We remind ourselves of that triumph tonight by taking rays of light that have left the star Arcturus during the period of that exposition (1893) and which have traveled at the rate of 186,000 miles a second until at last they have reached us. We shall use these rays to put into operation the mysterious forces of electricity which will make light our grounds ..."

The Carillon Tower at the Hall of Science (left) along with the Arcturus / observatory panel (left of center) are featured in this postcard from the time. Newberry Collection / Public domain

Visitors focused their attention on the giant illuminated panel above the speaker's platform that displayed a map of showing the locations of the four observatories. At 9:15 p.m. each of the telescopes dutifully focused Arcturus's light onto individual photocells and sent the feeble currents generated through telegraph lines to the fairgrounds. 

Postcard scene — real or imagined — that shows the Hall of Science and display panel (right) at night. Newberry Collection / Public domain

The switch was thrown, and a searchlight at top of the Hall of Science shot a brilliant beam of light across the sky. The crowd loved it so much that the nearby Elgin Observatory was pressed into service to make the cosmic connection during the remaining nights of the fair.

 I encourage you to strike up your own relationship with Arcturus. To gaze at the star and travel back in time 37 years ago (if you have that many!) as well as to look forward 37 years into the future if only to wonder what might be. I predict there will still be french fries, annoying pop-up ads and true friends, but I remain skeptical about the general use of jet packs.