Arc to Arcturus

Apr 27, 2015

Arcturus takes center stage in this shot
Credit NASA

  This is “Looking UP! in southern Colorado,” from the Colorado Springs Astronomical Society. I’m Hal Bidlack, and there are lots of reasons to look up!

Did you know that in 1933, the light from a star was used to turn on the lights at the Chicago World’s Fair? 

It’s true! The 1933 world’s fair was scheduled to start 40 years after the last world’s fair had occurred, in 1893. Looking for a way to generate publicity, the organizers of the 1933 event looked for a star about 40 light years away from Earth. They consulted with astronomers, and came up with the star Arcturus. On the night of May 27, 1933, several telescopes were focused on Arcturus, and the light from the star struck several photoelectric cells, which in turn switched on the floodlights at the world’s fair. As it turns out, they were off by a bit, as Arcturus is only 37 light years away, but it must have been an impressive thing to see!

Arcturus is the 4th brightest star in the sky, and the 2nd brightest visible to listeners in Southern Colorado. It’s easy to find. Just locate the big dipper, and follow the arc of the handle of the big dipper across the sky, and you’ll see Arcturus. “Arc to Arcturus,” you can’t miss it!

Arcturus is a very old star – somewhere between 6-8 billion years old! Our sun is only about 4.5 billion years old and the Earth is a bit younger still. So Arcturus is an ancient star, which has burned through its hydrogen fuel supply and is now burning helium, though even that will be exhausted before too many more billions of years pass by.

And Arcturus is moving. Fast. While nearly all of the stars in our Milky Way galaxy, including our sun, are slowly revolving pinwheel-style around the center of the galaxy, Arcturus is hauling at a speed of about 76 miles per second (that’s about 270,000 miles per hour) perpendicular to the galactic plane. It is cutting across the galaxy at a huge speed. In a few million years, it not only won’t be one of the brightest stars in Earth’s sky, it won’t be visible at all. It will have left the building, Elvis style

If you’d like to take a closer look at the Arcturus or any of the other wonderful and amazing things in the sky, please visit or for a link to information on our monthly meetings and our free public star parties! 

This is Hal Bidlack for the Colorado Springs Astronomical Society, telling you to keep looking up, Southern Colorado!