Celestial News: Boötes and the bears highlight May skies
For Steamboat Pilot & Today
There are 88 constellations in our sky, and only one of them begins with the letter B. It’s Boötes, the Herdsman (pronounced bo-oh’-teez), and it might be the most ancient of our constellations.
The name of Boötes has been uttered in this form for at least 3,000 years, as it first appears in Homer’s Odyssey. At that time, however, it most likely referred to the name of Boötes’ brightest star, Arcturus, rather than the entire constellation.
In Greek mythology, Boötes was considered a shepherd or a herdsman, chasing the Big and Little Bears around the pole of the sky with his two hound dogs, Asterion and Chara. These two pooches are found in their own small constellation nearby, named Canes Venatici, the Hunting Dogs.
Boötes is often identified with the mythological Greek hunter Arcas, a son of Zeus and a mortal woman named Callisto. When Zeus’ jealous wife, Hera, found out about the love child, she changed Callisto into a bear, destined to roam the forest forever. When Arcas grew up, he was out in the forest one day and saw a huge bear running toward him.
He prepared to fire an arrow to kill the bear, not realizing that it was his own mother who had recognized him from afar. Zeus intervened just in time, changed Arcas into a little bear, grabbed both bears by their short, stubby tails, slung them round and round and up into the heavens where they were transformed into the stars of our constellations Ursa Major and Ursa Minor, the Big and Little Bears. This launching technique explains how the celestial bears’ tails became so much longer than their terrestrial counterparts.
Locating Boötes and its brilliant star Arcturus is a snap. Just face the northeastern sky in the early evening and use the handle of the nearby Big Dipper as a pointer — follow the arc of the curved handle to find Arcturus. The stars of Boötes form the outline of kite-shaped figure, with Arcturus marking the bottom point of the kite.
Arcturus is the brightest star visible in the sky’s northern hemisphere and the second brightest star visible overall from Northwest Colorado. Only the Dog Star Sirius appears brighter in our sky. This prominent orange star is already in the advanced stages of life and has swelled up into an orange giant, 34 times larger than our Sun.
The name Arcturus is derived from the Greek word for bear, arktos. Literally, the name Arcturus translates into the “Bear Watcher” or “Bear Chaser.” Boötes is a cowboy, of sorts, chasing the two bears around the pole of the sky in a celestial bear round up.
The star Arcturus became famous when its light was focused through a telescope and used to switch on the lights of the 1933 World’s Fair in Chicago. This particular star was chosen because the starlight that arrived in 1933 was thought to have left Arcturus 40 years earlier during the previous Chicago World’s Fair in 1893. Modern measurements, however, place the star’s distance at 37 light-years instead of 40. Oops.
Jimmy Westlake retired from full-time teaching at Colorado Mountain College Steamboat Springs in 2017, after 19 years as their professor of physical sciences. His Celestial News column appears monthly in the Steamboat Pilot & Today. Check out Westlake’s astrophotography at jwestlake.com.
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