Western Slope Skies - Arcturus, the Time Machine

Jul 14, 2017

The summer night sky is teeming with bright stars, but one outshines them all and has stories to tell that rival its brightness. Head outside at nightfall and look almost straight overhead to spot the brightest star in the summer sky, the red giant, Arcturus.

Sporting a pale orange hue visible to the naked eye, Arcturus is one of the most fascinating stars in the night sky. An immense star roughly 25 times the diameter of our Sun, Arcturus is also a time machine that affords us both a look into the past and a glimpse into our distant future.

Celestially speaking, Arcturus is our next door neighbor, lying just 37 light years from Earth. A light year is the distance that light travels in one year, meaning the light you see from Arcturus tonight actually left the star 37 years ago, the same year that Mt. St. Helens unleashed its violent eruption and when VCRs still cost hundreds of dollars. Even light, travelling at the cosmic speed limit, takes decades to traverse even small portions of interstellar space.

Organizers of the 1933 Chicago World’s Fair took advantage of this idea to highlight advances in science and technology in a unique way. On the evening of the opening ceremony, four observatories focused light from Arcturus onto a photocell, creating an electric current that was used to activate the lights to the fair. Why Arcturus? At the time, astronomers believed Arcturus to be about 40 light years away. While we now know their measurements were off slightly, 40 years earlier Chicago had hosted another world’s fair, so the light leaving Arcturus in 1893 was arriving at Earth just in time to ceremoniously open Chicago’s second world’s fair.

And what about the future? Arcturus has nearly the same mass as the Sun, allowing us to use it as a guide to the ultimate fate of our own star. In about five billion years, when the Sun begins to run out of hydrogen fuel, it too will swell up into a red giant much like Arcturus is today. When this happens, Mercury and Venus will likely be consumed by the expanding Sun, making any remaining life on Earth very uncomfortable! 

Western Slope Skies is produced by members of the Black Canyon Astronomical Society. This segment was written by Zach Schierl and recorded by Art Trevena.