Ian Ridpath’s Star Tales

Hevelius’s depiction of Canes Venatici

Canes Venatici, the two hunting dogs of Boötes, was invented by Johannes Hevelius and first depicted in his Firmamentum Sobiescianum star atlas, published posthumously in 1690. The dogs are drawn as greyhounds, which hunt as a pair, and are seen in pursuit of the Great Bear. Hevelius named the northern dog Asterion and the southern one Chara, and included their names in his catalogue as though he regarded each as a sub-constellation. Asterion was a male dog, and Chara was female. Hevelius said Chara was the swifter of the two, and on his chart she runs ahead in pursuit of the bear.

In common with all Hevelius’s constellation figures, this one is drawn back to front, as it would appear on a celestial globe. Boötes stands on Mons Maenalus, a now-obsolete constellation that was also devised by Hevelius.

The brightest star of Canes Venatici is of 3rd magnitude and lies on the ring where the lead attaches to Chara’s collar. It was subsequently given the Greek letter Alpha by the English astronomer Francis Baily in his British Association Catalogue of 1845 as Hevelius did not use Greek letters on his charts or in his catalogue. The star is popularly known as Cor Caroli (Charles’s heart) in reference to the executed King Charles I of England, a name that was given to it by British astronomers before Canes Venatici existed.

The second-brightest star, 4th-magnitude Beta Canum Venaticorum, lies on Chara’s eye; it is officially named Chara. Ptolemy had listed these two stars in the Almagest as among eight ‘unformed’ stars outside Ursa Major. They can, for example, be seen as two open circles beneath the tail of the Great Bear on the charts of Albrecht Dürer and Petrus Apianus.

Hevelius did not say whether he was influenced by this globe from 1602 by the Dutch cartographer Willem Janszoon Blaeu, but it would not be surprising if he had seen it and borrowed the idea.

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