Celestial News: The Season of the Diamond
April 5, 2018
Each season brings its own unique geometrical pattern of bright stars into our early evening sky. Summer has its Summer Triangle, autumn has the Great Square of Pegasus, winter has the magnificent Winter Hexagon and spring offers the Spring Diamond.
The Spring Diamond asterism, also called the Virgin's Diamond, is marked at its corners by four of the brightest stars sparkling in our springtime sky: Arcturus, Spica, Cor Caroli and Denebola. Arcturus and Spica are easy to spot because of their flashy brilliance, and the curving handle of the Big Dipper points them out conveniently. Simply "follow the arc (of the handle) to Arcturus" and then "spike on to Spica."
The Spring Diamond also offers us the opportunity to identify four important constellations of the spring sky: Bootes (bow-oh-teez), Canes Venatici (cay'-neez ven-at'-ti-see), Leo and Virgo.
Let's begin with Arcturus, the star that forms the Diamond's easternmost tip. Arcturus is the alpha star in the constellation of Bootes, the Herdsman. Its name is derived from the Greek word for bear, arktos. Literally, the name translates into "the Bear Watcher." Bootes is a cowboy, of sorts, chasing the two bears around the pole of the sky with his two hunting dogs in a celestial bear round up.
Arcturus became famous in 1933 when its light was amplified through a telescope and used to turn on the lights of the Chicago World’s Fair. This particular star was chosen for the job because the starlight that arrived in 1933 was believed to have started its journey to Earth 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.
This bright orange star is already in the advanced stages of its life and has puffed up into an orange giant, 34 times larger than the sun. At a distance of 37 light years, Arcturus is the brightest star visible in the sky's northern hemisphere and the second brightest star overall visible from Northwest Colorado. Only Sirius, the Dog Star, appears brighter.
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Bootes' two hunting dogs can be found in the tiny, nearby constellation of Canes Venatici. The alpha star in Canes Venatici is none other than Cor Caroli, the star marking the northernmost tip of our Spring Diamond. Cor Caroli means "Charles' Heart." It was named in honor of King Charles I of England, or perhaps his son, Charles II.
Locate Cor Caroli by using the curved handle of the Big Dipper. If you imagine the Dipper's handle to be segment of a complete circle, Cor Caroli would lie near the center of this make-believe circle. Cor Caroli appears as a single star to the unaided eye, but a small telescope reveals it to be a lovely pair of stars. It is considered to be one of the most beautiful binary stars in the sky and is well worth a closer look through a backyard telescope.
At the western tip of the Spring Diamond is Denebola, the beta star in the constellation of Leo, the Lion. The name Denebola literally means "the Lion's Tail" and represents the tuft of hair on the end of the celestial lion's tail. Denebola is 36 light years from Earth, one light year closer to us than Arcturus, but appears considerably fainter.
Legend tells us that Leo fell from the sky to Earth like a meteor and roamed the countryside, terrorizing the peaceful inhabitants. Leo's hide was so tough that no spear or arrow could pierce it. Greek strongman Hercules managed to defeat the beast by strangling it with his bare hands, then he made a robe out of the lion's hide to protect himself from spears and arrows.
At the Spring Diamond's southern tip is the bright star Spica, the alpha star in our constellation of Virgo, the Virgin. Its icy blue color stands in sharp contrast to orange Arcturus. Spica is a blue supergiant star that shines from 260 light years away and is the tenth brightest star in our sky. The name Spica means "the Ear of Wheat" and comes from the same Latin root word as our word "spaghetti." I guess you could say that Spica is the "spaghetti star."
We call this constellation Virgo, but the virgin's name is actually Persephone (per-seff'-oh-knee). Greek mythology tells us that Persephone was the lovely, innocent daughter of Demeter, the goddess of the Earth. One day, Persephone was kidnapped by Hades, ruler of the dead, who took her into the underworld to be his wife. While there, Persephone made the mistake of tasting of the fruit that grew there and this doomed her to live in the underworld forever. Her mother was heartbroken, but was very determined to get her daughter back. She struck a deal with Hades, that he could have Persephone in the underworld for half of the year and the other half she would spend on Earth with her mother.
This legend was an early attempt to explain the cause of the seasons on Earth. When Persephone was with her mother, the Earth was warm, happy, and green, during the spring and summer. When Persephone left her mother and went to be with her husband in the underworld, the Earth grew cold, sad, and brown, as living things withered and died, during the fall and winter.
Jimmy Westlake retired from full-time teaching at Colorado Mountain College Steamboat Springs in 2017, after 19 years as a professor of physical sciences. His Celestial News column appears monthly in the Steamboat Today. Check out Westlake's astrophotography website at jwestlake.com.