Canes Venatici – the hunting dogs

December 10, 2017

Astronomy

There are a couple of hunting dogs which together form the constellation Canes Venatici. The north dog is named Asterion (little star) and the south dog is named Chara (joy). If you are looking for weird dog names for your new puppy, there you go. The allegory caught on back in 1687 when a Polish astronomer named Johannes Hevelius first drew the pair of hounds on his star maps.

The pooches are often shown on leashes held by the neighboring constellation Boötes. The dogs and their master are chasing Ursa Major, the Great Bear. The two brightest stars of the group make up the southern dog. On Ptolemy’s maps these stars are part of the areas he left without names, the celestial wilderness. For awhile there was a competing idea when a Dutch astronomer named Petrus Plancius added these stars to a constellation he called Jordanus, the river Jordan, but the dogs prevailed.

South dog’s collar has the brightest star of the group. It’s known as Cor Caroli. The name means “Charles’ Heart.” There is some confusion regarding which King Chuck it likely refers to, but most signs point to King Charles I of England, whose head and body went their separate ways in 1649. I think Cor Caroli may be the only star named after a major bodily organ of an actual monarch.

La Superba is a star in north dog which is known for being very red, and variable. It ranges in brightness from moderate to very dim over a period of 160 days. Why wasn’t this star named after someone’s heart? It has a beat. And it’s red. La Superba has finished turning its hydrogen core into helium, and also the subsequent conversion of that helium into Carbon, Nitrogen, and Oxygen. Now it’s living on the financial residuals of hydrogen to helium conversion in the upper layers thanks to all the left over heat from the advanced core. It’s basically spending the saved-up profits from an earlier economic investment.

The Giant Void, an extremely large empty place one billion light-years across, is located in this constellation. Depending on how our exploration of these things works out, it might the largest void ever, a thousand times bigger than average. It was discovered in 1988. If my wife and I had moved there in 1988 it would now be filled with all kinds of crap and we would looking at moving into a bigger void.

There are plenty of tourist attractions in the area of Canes Venatici. There is M3, a nice a globular cluster. There is M63, an excellent face-on spiral known as the Sunflower Galaxy. There is M106, which is a Seyfert galaxy, a diagnosis associated with a rather severe type of galactic heartburn.

Then there is M51, the Whirlpool Galaxy. This was the very first galaxy in which a spiral shape was noticed by a human. Irish astronomer Lord Rosse gets credit for that. In 1845 he said something like “Jesus Mary and Joseph this one’s gone all spyralish I’ll have me another Guinness.”

The Whirlpool Galaxy is amazing. It’s a must-see. There are two obvious parts, a large face-on spiral and a lesser but substantial orbiting dwarf galaxy. Then there is a third point of interest, a “bridge” of stars connecting the other two parts. When you find M51, the first test is to see just how well you can see the dim bridge. Here’s another valuable test. Just aim your telescope at M51 and show your friends. If they are not blown away, you need a new telescope.

Carpe Noctem

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