Large Dog

The constellation of the Large Dog is one of oldest the Constellation S, because of presence of Sirius, the most brilliant star of the sky. Near to the ecliptic , it is visible only a few months per annum with the latitudes close to 45° northern. It is towards the Solstice of summer (June 21st) that it is not visible. At the other dates, it is visible either very early the morning (fine of be - beginning Automne) or all the night (at the end of autumn beginning Hiver) or the evening (at the end of winter beginning of the Printemps).

History

The Large Dog having the most brilliant star of the sky is naturally one of the oldest constellations. It in any case formed part of the 48 constellations indexed by Ptolémée in its Almageste .

Two legends are superimposed to explain to which dog this constellation refers: first of all Laelaps, the dog of Actéon, or that of Procris, a nymph of Diane, or that given by the Dawn to Céphale, so much rapid which it was able to overcome the Fox with the race and which it was placed in the skies by Zeus in reward.

The second legend tells that it is about the gun dog of Orion, pursueing the Lièvre.

Observation of stars

; Localization of the constellation The localization is not difficult: Sirius being the most brilliant star of the night sky, the only difficulty can be its identification.

Sirius is located on the hexagon of winter, centered on Orion, of which it occupies the south-eastern angle. This star is in the southern prolongation of the " three kings mages" who form the cross-belt of Orion.

; Form constellation The principal stars form a definitely recognizable trapezoid, with of course Sirius which marks the neck of the dog (probably its brilliant medal), more in the South Wezen (δ CMa) which marks the base of the tail, and the two legs marked by Murzim (β CMa), the front leg, and Adhara (ε CMa), the back leg.

One rather easily distinguishes the end from the tail, Aludra (η CMa), located in the alignment of the back.

The remainder of the constellation is rather not very visible. The head of the dog forms a not very luminous triangle with the top of Sirius, and its back legs are prolonged to frame the constellation of the Colombe.

Principal stars

See also: List of stars of the Large Dog

Sirius (α Canis Majoris)

Sirius, the most brilliant star of the constellation of the Large Dog, is also the more brilliant vault of heaven. It is also the 6th star nearest to our Solar system, distant of only 2,67 PC. Its name derives from a Greek term, sireios , meaning extreme .

It is a star doubles:

Sirius has is a white star of the principal sequence, extremely visible because it is very close, but not much larger than the Sun;
Sirius B , magnitude 8,44, is a white Naine which spends 50 years to carry out a revolution around Sirius has , from which it is distant from 8 to 31 ua. Sirius B was discovered in 1862 by Alvan Clark, but Friedrich Bessel had the noted first of the disturbances related to a companion in the position of Sirius.

Other stars

The constellation of the Large Dog is perhaps not very large, but it contains a great number of visible stars, and several of them bear a proper name: Murzim (β CMa), Muliphen (γ CMa), Wezen (δ CMa), Adhara (ε CMa), Furud (ζ CMa), Aludra (η CMa).

ο CMa gathers actually two stars distinct, distant of the Earth of approximately 2.000 light-years, but separate one and the other 70 light-years. ο² The CMa, most brilliant (magnitude 3,02) is a blue Supergéante, ο¹ CMa (magnitude 3,89) is an orange supergéante.

τ CMa is a multiple star: the most brilliant star is made of a pair of stars from magnitude 4,9 and 5,3 separated by 233 ua, around which orbit a star from 10th magnitude to more than 13.000 ua. The most brilliant star of the pair is itself doubles (two distant stars from approximately 9 ua over one 155 days period), and one as of these two stars also has a close companion, since it makes of it the turn in 1,28 days with the distance from 0,1 ua only.

Celestial objects

There are not many celestial objects in the constellation of the Large Dog. In lower part of Sirius nevertheless the open Amas is M41, magnitude 4,6.

In 2003 was discovered small a irregular Galaxie known as of the Large Dog, located at only 13 kpc of the Galaxie (thus, to a few hundred parsecs of the outside of the disc), nearest known at present.

See too

List of stars of the Large Dog

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