Canes Venatici

Canes Venatici

Transit Date of principal star:
5 April

Canes Venatici is one of those obscure constellations introduced by Johannes Hevelius in 1690. It represents the two dogs Asterion and Chara, both held on a leash by Bootes as they apparently chase the Great Bear around the North Pole.

With one exception, the constellation's stars are quite faint, fourth- and fifth-magnitude stars. There are only three Bayer stars, yet several notable binaries can be found, as well as a famous variable and a number of interesting deep sky objects as well.

Alpha Canum Venaticorum is popularly called Cor Caroli (Heart of Charles). Most sources give Edmund Halley the credit, naming it after King Charles II after the restoration of the monarchy in Britain in 1660. (Some say, however, that the reference was initially meant to commemorate Charles I, after his execution.)

The star has a visual magnitude of 2.9 (variable), a distance of 110 light years, and roughly the same size as our Sun. It is also a splendid double with, perhaps, a subtle colour contrast (discussed below).

Double stars in Canes Venatici:

Canes Venatici has several very attractive binaries. The Binocular Section, linked at the bottom of this page, gives full details.

Variable stars in Canes Venatici:

The constellation contains one of the more interesting semi-regular stars, Y CVn, called La Superba by its admirers. One look and you will understand why: the star is an unusually vivid red.

Y CVn is classified as an SRb star. Such stars are known to have several periodic cycles, superimposed on each other. Basically, it changes in magnitude from 7.4 to 10.0 every 157 days. (However an update published in Budapest, in the Information Bulletin of Variable Stars, #2271, has reassessed the period at 251.8 days.)

Alpha2 CVn is the prototype of a class of variables. Such stars usually have a spectrum from B9 to A5, are unusually abundant in particular heavy metals and deficient in common elements. Alpha2 has an abundance of silicon, europium, and mercury, and oscillates in magnitude from 2.84 to 2.98 every 5.5 days.

Deep Sky Objects in Canes Venatici:

There are five Messier objects in this constellation, and many more deep sky objects worthy of attention.

M3 (NGC 5272) is a wonderful globular cluster found roughly halfway between Cor Caroli and Arcturus (in Bootes). Considered one of the finest globular clusters in the entire heavens, you'll need a large scope to resolve its individual stars. The cluster is about 45,000 light years away.

M51 (NGC 5194) or The Whirlpool Galaxy is the finest galaxy in Canes Venatici.

This spiral, found just southwest from the tip of the Big Dipper's handle, was the first spiral galaxy to be discovered (in 1845 by Lord Ross at his castle in Ireland).

Some say the galaxy is 14 million light years away, others that it is twice that. In any case, you'll need a large telecope and a fine evening to enjoy its delicate detail, which includes an appendage system (NGC 5195), another galaxy seemingly hanging onto one of its extended arms.

M63 is sometimes called the Sunflower Galaxy, by its numerous arms, which Burnham describes as "reminiscent of showers of sparks thrown out by a rotating fiery pinwheel". Fairly bright, at 8.1 magnitude, it has a very condensed centre. The galaxy is found five degrees north-northeast of Cor Caroli.

M94 is another spiral, seen practically face-on, and sometimes described as "comet-like". This is a very compact circular spiral and very bright (8.1 magnitude). To find it draw a line between Cor Caroli and beta CVn, and at the half-way point draw a perpendicular off to the northeast. About two degrees up this perpendicular is found M94.

M106 (NGC 4258) is another bright spiral. Burnham doesn't list this object as a Messier, but gives a fine photograph (p 375). The galaxy is six degrees north north-west of beta CVn.

Below are listed a selected number of galaxies considered the best of the non-Messiers.

NGC 4244: a large edge-on spiral, found eight degrees west of Cor Caroli.

NGC 4485 and NGC 4490 are two splendid galaxies in the same field: 4485 is more compact (this one is sometimes called the Cocoon Galaxy), while 4490 is larger and brighter. Located less than one degree northwest of beta CVn.

NGC 4631: very large and bright, seen edge-on. Found in a rather barren field, six degrees south of Cor Caroli and two degrees west. In the same field are two more galaxies, NGC 4656 and 4657, just southwest of 4631.

For a closer appreciation of Canes Venatici, visit the Binocular Section.

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