Jimmy Westlake's Celestial News column appears Tuesdays in the Steamboat Today.
Find more columns by Westlake here.
Each season of the year brings its own unique asterism into our early evening sky, and each one is a geometrical pattern made up of bright stars from different constellations. Summer has its "Summer Triangle," autumn has the "Great Square of Pegasus," winter has the magnificent "Winter Circle" and spring offers us the "Spring Diamond."
The Spring Diamond asterism is marked at its corners by four of the brightest stars lighting up the spring sky. Their names are 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 of the handle 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 life and has swelled up into an orange giant, 34 times larger than our Sun. At a distance of only 37 light years, Arcturus is the second brightest star visible from northwest Colorado.
Spica marks the Diamond's southern tip. It's icy blue color stands in sharp contrast to orange Arcturus. Spica is a blue supergiant star that lies 260 light years away and is the tenth brightest star in our sky.
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, named in honor of King Charles II of England. Locate Cor Caroli by 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 finest double stars in the sky and is well worth a glimpse through a telescope.
Denebola marks the Diamond's western tip. The name Denebola literally means "the tail of the lion." 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 are in the constellation of Virgo.
Each of the four corners 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. Happy Diamond hunting!
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published on the Web sites of CNN.com, NASA's "Astronomy Picture of the Day," Spaceweather.com, Space.com, Discover.com and in Sky & Telescope, Astronomy, Night Sky, Discover and WeatherWise magazines. His "Celestial News" article appears weekly in the local Steamboat Pilot newspaper. He also records a radio spot called the "Cosmic Moment" for the local radio station "The Range" at 107.3 FM.