Jimmy Westlake: Bootes, the Bear Watcher
April 10, 2012
Steamboat Springs — There are 88 constellations in our sky, and only one of them begins with the letter B. Do you know what it is?
It's Bootes (pronounced boh-oh-teez) the Herdsman, and it could be the most ancient of our constellations.
The name of Bootes has been uttered in this form for at least 3,000 years, first appearing in Homer's "Odyssey." But at that time, it likely referred to the name of Bootes' brightest star, Arcturus, rather than the entire constellation.
In Greek mythology, Bootes was considered a shepherd or a herdsman, chasing the Great and Little Bears around the pole of the sky with his two leashed pooches, Asterion and Chara. The two hunting dogs are found in the small nearby constellation named Canes Venatici. Bootes is often identified with the Greek hunter Arcas, the illegitimate 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 great 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 hold of 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 Ursa Major and Ursa Minor, the Great and Little Bears. This explains how their tails got to be so long.
Locating Bootes and its bright star Arcturus is a snap. Just use the handle of the nearby Big Dipper as a pointer — follow the arc of the curved handle to Arcturus.
This prominent orange star already is in the advanced stages of life and has swelled into an orange giant 34 times larger than our sun. Arcturus is the brightest star visible in the sky's northern hemisphere and the second-brightest star visible from Northwest Colorado.
The name Arcturus is derived from the Greek word for bear, "arktos." Literally, the name Arcturus translates into "the bear watcher." Bootes is a cowboy of sorts, chasing the two bears around the pole of the sky in a celestial bear roundup.
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 place the star's distance at 37 light years instead of 40. Oops.
Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. Check out Westlake’s astrophotography website at http://www.jwestlake.com.