Bootes, pronounced boo-oot-tes, is a constellation that is supposed to outline the figure of a hunter chasing neighboring Ursa Major, otherwise known as the Big Bear.
Instead, as you gaze upon Bootes after evening twilight in the low western skies, you’ll see a giant kite, with the very bright star Arcturus at the tail of the kite.
All summer, the kite has been flying high in the nighttime skies, but as we move toward colder times, the kite is starting to fall. This is really your last chance to see the celestial kite in the evening until next spring, when it pops up in the eastern heavens.
There’s no mistaking Arcturus. It’s the brightest star in the evening skies right now. There are brighter objects in the western sky in the vicinity of Arcturus, but they are planets.
In the low southwest, Jupiter still shines brightly in the early evening, and very low in the southwestern sky you may see the very bright Venus before it slips below the horizon right after evening twilight.
One sure way to know you’re looking at Arcturus and not at one of the planets, is to use the Big Dipper, which also doubles as the rear end and tail of Ursa Major. Just extend the arc of the Big Dipper’s handle beyond the end of the handle and you’ll run right into Arcturus. Just remember “arc to Arcturus.”
A noticeably orange hue tells astronomers that Arcturus is a cooler star, but star colors are subtle to the naked eye.
Take a small telescope or an average pair of binoculars and scan across any part of the sky, and you’ll run into stars with various washed-out shades of blue, orange and red.
Just by looking at a star’s color, you can tell if it is a hotter or cooler nuclear-powered ball of gas. Bluer stars are hotter and reddish-orange stars are cooler.
It’s just like a campfire: The hottest part of the fire will be the inside blue flames, with the cooler orange flames on the outside, closer to where you roast your marshmallows.
Even with its orange hue, astronomers describe Arcturus as a red giant star, a bloated star that’s starting to run out of hydrogen fuel at its core. The details are a little complex, but here’s what happens:
As the core begins to collapse after the hydrogen is spent, heat is released into outer edges of the star, producing nuclear fusion and energy and forcing the star to bulge out way beyond its original size.
Arcturus is more than 25 times the diameter of our sun, but it’s a lot cooler than our home star, with a temperature just above 7,000 degrees. The sun is over 10,000 degrees.
As you gaze at Arcturus, you’re looking at a star more than 212 trillion miles away, and because of the speed of light, you’re not seeing it as it is tonight, but as it was in 1972. Richard Nixon was still our president.
In mythology, Bootes has been portrayed as the son of the goddess Demeter and as the inventor of the plow, which earned him a spot in the heavens. He also is depicted as a hunter following the Great Bear around the skies.
If you do an Internet search on Bootes, you can turn up even more stories and names for this constellation.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and author of the book, “Washington Starwatch,” available at bookstores and at his Web site www.lynchandthestars.com
The Everett Astronomical Society welcomes new members and puts on public star parties. The Web site is members.tripod.com/everett_astronomy.
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