Under The Dipper’s Handle, Part 1
Though it lacks the opulent wonders of winter, the northern spring sky holds sights that are far more subtle and well worth exploring. Today, the first part of a tour under the handle of the Big Dipper, where you’ll discover a fine double star and a strange poppy-red carbon star burning off the last of its nuclear fuel.
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The Basics
• Find the Big Dipper and look about 12 degrees below the two end stars in its handle, Alkaid and Mizar. (Twelve degrees is a little more than the width of your fist). There, you’ll see two stars in a line roughly parallel with the Dipper’s handle. These two stars are the brightest of the constellation Canes Venatici, the Hunting Dogs.
Under the Dipper’s Handle (click to enlarge)
• The brighter of the two stars is Cor Caroli (the “Heart of Charles”), named by Edmund Halley after the martyred English King Charles I. Cor Caroli is a pretty double star, easily split in a small telescope even at 30-40x. The blue-white primary shines at magnitude 2.9; the fainter yellow companion is magnitude 5.6 some 19 arc-seconds away from the primary.
• The brighter of the two components of Cor Caroli is formally called alpha Canes Venaticorum. It’s an unusual type of variable star with an intense magnetic field that creates enormous “starspots”, similar to our sun’s sunspots. The starspots move in and out of view as the star rotates, causing variability in overall brightness.
A Deeper Look
• Some 6 degrees northeast of Cor Caroli, you’ll find the unmistakable dull-red glow of the cool red giant star Y Canes Venaticorum. You’ll need a pair of binoculars or a small telescope to see it: it’s just beyond the reach of the unaided eye.
• Also called “La Superba”, the cool variable star has an atmosphere rich in carbon compounds that block all but red and infrared light from shining through. This makes the star far redder than nearly any other star in the sky.
• La Superba has begun to eject its outer layers and appears ready to form a new planetary nebula.
Good To Know
The carbon in the atmosphere of La Superba was likely produced by nuclear fusion of helium in the star’s core. Deep zones of convection dredged up the carbon into the atmosphere.
Personal View
La Superba is on the “must see” lists of many stargazers. It offers a grand view of a strange star in its final moments of life, and reveals the remnants of processes that light all stars in the night sky.
To Be Continued… In the next issue, we’ll tour 3 galaxies under the Dipper’s handle, including the famous Whirlpool Galaxy.
