Let’s take a look at the ancient constellation Coma Berenices, a faint group of stars tucked under the handle of the Dipper halfway between the stars Arcturus and Denebola in Leo’s hindquarters. There is something for everyone here: history and legend, a beautiful naked-eye star cluster that invites careful inspection, and dozens of galaxies to explore with a modest telescope. And armchair astronomers can contemplate the immensely distant Coma Cluster of Galaxies, some 300 million light years away, that first yielded evidence for the mysterious dark matter that makes up a good portion of the universe.
Coma Berenices is one of the few constellations based on an historical figure. In 243 B.C. King Ptolemy of Egypt (not Ptolemy the famous astronomer) marched away to war in Syria to avenge the death of his sister. His young Queen Berenice was concerned for her husband’s safety and vowed to sacrifice her beautiful long, amber hair to the goddess Venus if she granted his return and victory over his enemies. Ptolemy returned in triumph, and Berenice, true to her vow, cut off her hair and bore it to the Temple of Venus. But the same night it disappeared, likely stolen by a mortal. The king was furious, and the queen wept bitterly over the loss.
There is no telling what might have happened to the guardians of the temple had not a celebrated astronomer named Conon of Samos taken the young king and queen aside in the evening and showed them the missing locks shining transfigured in the sky. He assured them that Venus had placed Berenice’s lustrous hair among the stars, and, since they were not skilled in celestial lore, the royal couple were quite ready to believe that the silvery swarm they saw near Arcturus had not been there before. So for centuries the world has recognized the constellation of Berenice’s Hair.
Like the constellation Taurus, Coma Berenices is almost entirely composed of a nearby star cluster. The group, cataloged at Melotte 111, is “Y-shaped” in binoculars and contains a fine star field. As a test of vision, see how many of the stars you can resolve without optics if you have dark sky. You can see the cluster north and east of the back end of the constellation Leo and south and slightly west of the handle of the Big Dipper. There are a few stars in the constellation beyond the cluster: the three main stars of the constellation are α (alpha) Comae (Diadem), β (beta) Comae, and γ (gamma) Comae (Al Dafirah). They’re all 4th magnitude stars and they’re hard to see in anything but quite dark sky.
For binocular observers, the stars that represent Berenice’s Hair are reason enough to explore this part of the sky. But observers with a telescope (and a good star map or go-to mount) are rewarded with half a dozen or more splendid galaxies sprinkled behind these foreground stars. These galaxies are mostly outliers of the Virgo Galaxy Cluster and are about 55-65 million light years away. We see so many galaxies here because this constellation lies at the “north galactic” pole, a point which marks one axis of the rotation of our galaxy. Here we look directly out of the Milky Way at a right angle to its starry plane.
And there is deeper quarry here, too. Between the stars β Comae and γ Comae, in a tight patch of sky closer to the former, lie thousands of faint galaxies in the Coma Galaxy Cluster. These galaxies lie at a distance of some 300 million light years, so the light we see from these objects is older than the oldest dinosaur fossils. With a 15″ scope, you can see a handful of these galaxies visually in a single field of view. A study of this cluster in the 1930s yielded the first glimmer of evidence of unseen mass in the universe, a mass which the Swiss astronomer Fritz Zwicky called dunkle Materie, which is German for “dark matter”.
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