What is your favorite flavor of ice cream? Mine is maple and walnut, but I wouldn’t turn down a bowl of plain vanilla either. I like mine wrapped in a waffle cone. The kind with a chocolate chip waiting for you at the pointed end. What a satisfying finish!
Since we are well into ice season (do we need a season?), it seems like the time is right to introduce Boötes the Shepherd, a constellation that grows in prominence in May and June.
Two things about Boötes: people, even amateur astronomers, are a bit unsure of its pronunciation, and it’s shaped like – you guessed it – an ice cream cone. Don’t be intimidated by the umlaut above the “o”, as if you had to know German to say it correctly. It’s there to remind us to voice each “o” separately instead of executing them. So it’s bo-oh-teez. Not BOO-teez. I know. It still seems a bit ridiculous.
Finding the constellation is super simple. The next clear night as soon as it gets dark, face south and look straight up. You will see a bright orange star. It is Arcturus (arc-TOUR-us), the fourth brightest star in the night sky. It is only 36.7 light years from Earth, one of the reasons it shines so brightly. Another is that it’s a behemoth – a giant orange star 25 times bigger than the sun that emits around 100 times more light.
Now close your fist and hold it up to the sky. A fist above and slightly to the left of Arcturus, you will see a fainter second magnitude star named Izar on the left side of the cone. From Izar, connect the dots to arrive at Nekkar, the “cherry” perched atop an imaginary mound of ice cream. Then star jump to the right side of the cone, past Seginus and back to Arcturus. Two “rays” of stars come out from each side of the star. Think of them as describing a cardboard cone holder.
That’s all we can say about it. The entire constellation spans about two and a half fists or 25°. Boötes has long been associated with the Big Dipper, the Big Dipper, the brightest part of which we know as the Big Dipper. In late winter, when Boötes first rises in the east after dusk, you can easily find Arcturus by simply following the arc of the ladle handle toward the horizon.
Boötes depicts an executioner or herder, but is better known as the Bear Guard because the figure appears to follow the bear as it orbits the North Star during the year. The name Arcturus suggests this – it means bear keeper from ancient Greek “arktos” (bear) and “ouros” (watcher).
All the stars are in motion as they orbit the center of the Milky Way, but you’d never know that at a glance. Even the nearest ones are so distant that a human lifetime is far too short to see them change position. Orion looks the same when you draw Social Security as the day you first looked into your mother’s eyes.
That said, Arcturus is one of the fastest. Not only is it close, but it also crosses our field of vision at the rate of just over a tenth of a full moon’s diameter per century. This adds up to two full moon diameters or 1° every 1,500 years. Since ancient Greece, Arcturus has slipped more than 1° to the southwest. A sharp-eyed observer would have no problem detecting its movement over this period of time. But until we have a time machine, I’m afraid we’ll have to settle for a few select telescopic stars if we want to see movement in our lives.
Arcturus is currently near its closest point to Earth and glows with a bright, warm glow. In 150,000 years, when it is considerably farther away, it will be too faint to see with the naked eye – our distant descendants won’t even notice it. All the more reason to step out now to enjoy the Herdsman and Bear Star.
“Astro” Bob King is a freelance writer for the Duluth News Tribune.