A small and compact constellation of the southern hemisphere.
Canis Major contains several bright stars making
it conspicious in the night sky. The brightest of all stars, Sirius,
belongs to this constellation.
It borders to Monoceros in the north, Lepus to the west and Columba to the southwest while the eastern border is covered by Puppis, therefore it streches roughly from RA = -11 degrees to RA = -33 degrees and Decl = 6h 15m to Decl = 7h 30m, respectively.
Together with alpha CMi (Prokyon) and alpha Ori (Betelgeuze) alpha CMa forms the so called Winter Triangle.
Stars and objects
The star alpha CMa, commonly known as Sirius
(from greek sireios meaning "the sparkling"), is the brightest star
in the night sky. It apparent magnitude is -1.5 mag. Sirius also belongs to
the nearest stars with a distance of just 8.7 light years. This white star
has a companion of 8th mag at a distance of approximately 10''. The companion,
a white star usually called Sirius B, is not easy to resolve.
Amateur scopes are necessary to make it visible as the companion is simply
outshined by the main star. Sirius B was discovered 1862 by
Alvan Clarke. Bessel had already noted that there must be a companion as
observations showed that Sirius was not standing still in the sky but seemed
to pursue a small orbit. Furthermore according to the observations both
stars had the same surface color (i.e. same surface temperature), yet the
companion was not easy to see. The reason is the small size ot the star.
It belongs to a special class of stars called White Dwarfs.
The two stars revolve each other about every 50 years.
Beta CMa, common name Mirzam (greek: the announcer (of Sirius)), is a blue giant of 2.0 mag.
Another double is epsilon CMa: Adhara (meaning: the virgins). The blue giant of 1.5 mag has an 8th mag companion which is difficult to observe as it nearly vanishes in the glare of the main star.
In the neighbourhood of delta CMa, called Wezen (a yellow supergiant of 1.9 mag; it lies about 3000 light years distant) several interesting stars and objects can be found:
As the name associates Canis Major (lat.: canis=dog, major=greater)
is thought to be one of the hunting dogs of
The second dog is Canis Minor.