Alpha Canis Majoris


Distance (Light Years) 8.60 ± 0.04
Apparent Magnitude -1.44
Color (B-V)0

Names For This Star

Sirius comes from the Greek. According to Allen the etymology and meaning of the name is uncertain. Sirius is also called the Dog Star by virtue of the name of the constellation in which it lies.

Other names for Sirius are Canicula - which is Latin and means "The Little Dog" - and Aschere which derives from the Arabic Al Shira or Al Sira. The Arabic name is again of uncertain derivation and meaning; it may be related to the Greek name Sirius for the star.

Description of the Star

Sirius is a white A1Vm main sequence star having 22 times the luminosity of the sun and 1.6 times the sun's diameter. The spectral type implies an effective temperature of 9600 K and a mass about twice that of the sun.

Sirius is one of the nearest stars. See this German site for a nice three-dimensional representation of our nearby neighbor stars.

Sirius B or The Pup

Sirius is a double star. The companion, Sirius B, is also known as "The Pup," since it is the companion to the The Dog Star. Sirius B has a Apparent Magnitude of 8.49, corresponding to a luminosity 1/400 times that of the sun.

Sirius B reveals with a 50 year period in an orbit with a separation of about 20 AU between the two stars. This distance is approximate the same as the distance between the sun and Uranus.

According to Burnham the dynamics of the orbit indicates that the mass of the A star is 2.35 times the mass of the sun, while the B star has 98% of the mass of the sun.

A White Dwarf Star

According to the The Bright Star Catalog Sirius B has an effective temperature of about 32,000 K making it much hotter than the sun so that the star emits about 900 times more radiant energy per square meter of surface than the sun does. The very small luminosity of the star then must mean that the star has a very small surface area, that is, that the star is quite small in size. This type of star is known as a white dwarf.

Sirius B must be a star having almost the mass of the sun packed into a volume smaller than that of the earth. The density of Sirius B must correspond to about 5000 tons per cubic inch.

A white dwarf star like Sirius B is a stellar corpse that is very slowly cooling by the radiation of heat.

More on white dwarf stars.

Other Designations For This Star


9 Canis Majoris

Hipparcos Identifier (HIP Number)


Harvard Revised (HR Number)


Henry Draper Catalog (HD Number)


Bonner Durchmusterung (BD Number)

BD-16 1591
Smithsonian Astrophysical
Observatory compendium (SAO Number)

Fundamental Katalog (FK5 Number)



Copyright © 1998 - 2010 by Arnold V. Lesikar,
Professor Emeritus
Dept. of Physics, Astronomy, and Engineering Science,
St. Cloud State University,St. Cloud, MN 56301-4498

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