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Canis Major


[Pic]

Abbreviation:
CMa
English name:
Larger Dog
Coordinates
see Stellar data

Particulars:

General:

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:

  • The variable star EW CMa.
  • The variable star UW CMa.
  • The star cluster NGC 2362. This nice little cluster of about 40 stars surrounds the star tau CMa, a blue giant of 4th mag. The cluster can be spotted by binoculars or small scopes.

    Another notable star cluster is M41. Its a larger cluster with the brightest stars of about 7th mag. Under good conditions it is visible to the naked eye. A good view is obtained by small scopes or binoculars: the brightest stars seemed to be arranged in chains.
    In 2003 an international team of astronomers discovered a small irregular galaxy in this constellation. It is only 42,000 light years away making it to the nearest neighbour galaxy to our own one.

    Mythological Background:

    As the name associates Canis Major (lat.: canis=dog, major=greater) is thought to be one of the hunting dogs of Orion. The second dog is Canis Minor.

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    C. Kronberg --- 29.12.2003 --- smil