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Astro Bob: Meet Boötes, the ice cream cone constellation

I bet you've never seen the constellation Boötes, but it's easier than you think. Piggyback on Arcturus and you're there.

Boötes and Arcturus
Shaped liked an ice cream cone, Boötes the Herdsman might be tricky to find if it weren't for Arcturus, the fourth brightest star in the sky. The orange-red luminary shines high in the southern sky as soon as it gets dark.
Contributed / Stellarium
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What's your favorite ice cream flavor? Mine is maple walnut, but I wouldn't turn away a bowl of plain vanilla either. I like mine packed into a waffle cone. The kind with a nugget of chocolate waiting for you at the pointy end. What a satisfying finish!

Since we're well into ice cream season (do we need a season?) it seems a good time to introduce Boötes the Herdsman, a constellation that reaches prominence in May and June.

Ice cream cone
Boötes and an ice cream cone share a similar shape. The constellation offers a more generous scoop of ice cream than this modest treat. Arcturus shines at the cone's narrow tip.
Contributed / Bob King

Two things about Boötes: people, even amateur astronomers, are a little unsure of its pronunciation, and it's shaped like — you guessed it — an ice cream cone. Don't be intimidated by the umlaut over the "o," as if you have to know German to say it properly. It's there to remind us to voice each "o" separately instead of running them. So, it's bo-OH-teez. Not BOO-teez. I know. It still sounds a little ridiculous.

Y asterism
You can connect the brightest stars in Boötes and neighboring constellation Corona Borealis the Northern Crown to form an asterism shaped like the letter "Y."
Contributed / Bob King

Finding the constellation is super simple. The next clear night as soon as it gets dark, face south and look straight up. You'll see a bright, orange star. That's Arcturus (arc-TOUR-us), the fourth brightest star in the night sky. It's only 36.7 light-years from Earth, one of the reasons it shines so brightly. Another is that it's a behemoth — an orange giant star 25 times larger than the sun that radiates about 100 times more light.

Now make a fist and hold it up to the sky. One fist above and slightly left of Arcturus you'll 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-hop down the cone's right side past Seginus back to Arcturus. Two "spokes" of stars poke out from either side of the star. Think of them as outlining a cardboard cone holder.

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Arc to Arcturus
In winter you can find Arcturus by following the arc of the Dipper's Handle. Boötes lies on its side in the eastern sky at that time of year.
Contributed / Bob King

That's all there is to it. The entire constellation spans about two-and-a-half fists or 25°. Boötes has long been associated with the Ursa Major the Great Bear, 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 Dipper's Handle toward the horizon.

Boötes myth
Boötes is depicted with Canes Venatici the Hunting Dogs and Coma Berenices (Berenice's Hair) in a 19th century star atlas.
Contributed / Urania's Mirror, William Jamieson

Boötes represents a headsman or cattleman, but it's better known as the Bear Guard because the figure seems to follow the Bear as it circles around the Pole Star during the year. The name Arcturus suggests this — it means Guardian of the Bear from the Ancient Greek "arktos" (bear) and "ouros" (watcher).

All stars are on the move as they orbit the center of the Milky Way Galaxy, but you'd never know it at a glance. Even the closest are so far away that a human lifetime is much too short to see them shift position. Orion looks the same when you draw Social Security as it did the day you first gazed into your mother's eyes.

Arcturus moves!
Compare these two maps of Boötes from 300 B.C. and today, and you'll see how Arcturus has moved a little bit to the southwest, subtly changing the constellation's shape.
Contributed / Stellarium

That said, Arcturus is one of the faster-moving ones. It's not only close but also traveling across our line of sight at the rate of a little more than one-tenth of a full-moon-diameter per century. That adds up to two full-moon-diameters or 1° every 1,500 years. Since ancient Greek times, Arcturus has slid more than 1° to the southwest. A sharp-eyed observer would have no problem detecting its movement over that span of time. But until we get a working time machine I'm afraid we'll have to settle for a few select telescopic stars if we want to see one move in our life time.

Arcturus is currently near its closest point to Earth and shines with a bright, warm radiance. In 150,000 years, when it's 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 get out there now to enjoy the Herdsman and Bear Star.

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"Astro" Bob King is a freelance writer for the Duluth News Tribune.

Related Topics: SCIENCE AND NATURE
"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune.
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