Jimmy Westlake: Spring’s diamond in the sky
April 25, 2016
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 us 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 the spring sky: Arcturus, Spica, Cor Caroli and Denebola.
Arcturus and Spica are easy to spot, not only because of their flashy brilliance, but because the curving handle of the Big Dipper points them out for us so conveniently. Simply "follow the arc to Arcturus" and then "spike on to Spica."
Arcturus forms the Diamond's eastern tip. 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 our sun. At a distance of only 37 light years, Arcturus is the brightest star visible in the sky's northern hemisphere and the second brightest star visible overall from northwest Colorado.
Spica marks the Diamond's southern tip. 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 10th 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 Spica is the "spaghetti star."
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The other two stars in the Diamond are trickier to locate because they aren't quite as bright as Arcturus and Spica. The northern tip of the Diamond is marked by the star Cor Caroli, or Charles' Heart, and was named in honor of King Charles I of England, or perhaps his son, Charles II.
Locate Cor Caroli by once again using the curved handle of the Big Dipper. If you imagine the Dipper's handle to be an arc of a complete circle, Cor Caroli would lie near the center of this circle. Cor Caroli is one of the most beautiful double stars in the sky and is well worth closer scrutiny through a backyard telescope.
Denebola marks the Diamond's western tip. The name Denebola literally means "the lion's tail." It represents the tuft of hair on the end of the tail of Leo the Lion. Denebola is 36 light years from Earth, one light year closer to us than Arcturus.
Near the center of the Diamond lies the star Vindemiatrix, the "grape gatherer." Both Vindemiatrix and Spica belong to the constellation of Virgo.
Each of the four corner stars of the Diamond falls in a different constellation so, once located, the Spring Diamond can help you find many other gems of our springtime sky.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. His "Celestial News" column appears weekly in Steamboat Today. Check out Westlake's astrophotography website at jwestlake.com.