Universe Guide

Sirius (Alpha Canis Majoris) - HD48915 - HIP32349 - HR2491

Sirius (Alpha Canis Majoris) is a blue less luminous star that can be located in the constellation of CanisMajor. It is the 2nd brightest star in the night sky. Alpha Canis Majoris is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR2491. HIP32349 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD48915. Sirius has alternative name(s), 9 Canis Majoris , 9 CMa.

Sirius is also known as the Dog star, after all it is in the Big Dog constellation of Canis Major. It is widely known in part as it is the brightest star in the night sky, it is almost twice as bright as the next brightest star, Canopus. It is also one of our nearest neighbour stars, not as close as Rigil Kentaurus (Alpha Centauri) but still close. The only thing that is brighter excluding the moon is the planet Venus. It is moving closer towards us but won`t for a long time, longer than you and I will be on this planet so nothing to worry. 1. Sirius is a Double Star System with the smaller star being a white dwarf star having used up all its hydrogen.

Sirius in Fiction

Being the brightest and one of the most well known, it has become of interest by science fiction writers, for example, the lizard Visitors from V come from a planet orbiting this star. JK Rowling, author of the Harry Potter books has a character Sirius Black who name is inspired from this star. There are also other stars that have been the inspiration for characters such as Regulus Black. Sirius isn`t just limited to being mentioned in these fictions, the star is mentioned elsewhere. Sirius gets mentioned in Star Trek but there`s no real stories based in the Sirius Solar System excluding the cartoon series and extended universe. ref:Memory Alpha.

Sirius on the Move

Sirius is currently moving towards us but don`t fear a solar apocalypse, it will never collide with our Sun. It is moving at a very slow speed of 5.5 km/s and the closest it will ever get to us is 7.8 Light years, down from 8.6 that it is now. It will continue to be the brightest star in the night sky for at least another 90000 year after which point Delta Scuti will then take on that title. ref:StackExchange

Location of Sirius

The location of the star in the galaxy is determined by the Right Ascension (R.A.) and Declination (Dec.), these are equivalent to the Longitude and Latitude on the Earth. The Right Ascension is how far expressed in time (hh:mm:ss) the star is from celestial equator. The Declination is how up or down compared to the celestial equator and is expressed in degrees. For Sirius, the location is 06h 45m 09.25 and -16 d 42`47.3 .

Proper Motion of Sirius

All stars like planets orbit round a central spot, in the case of planets, its the central star such as the Sun. In the case of a star, its the galactic centre. The constellations that we see today will be different than they were 50,000 years ago or 50,000 years from now. Proper Motion details the movements of these stars and are measured in milliarcseconds. The star is moving -1,223.00 ± 001.00 towards the north and -546.00 ± 002.00 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Sirius

Sirius has a spectral type of A0m.... This means the star is a blue coloured less luminous star. The star has a B-V Colour Index of 0 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 10,293 Kelvin.

Sirius has been calculated as 1.51 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,047,827.16.km.

The star is a multiple star system, it has at least the following companions in close orbit, Sirius B.

Sirius Apparent and Absolute Magnitudes

Sirius has an apparent magnitude of -1.44 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. If you used the 1997 Parallax value, you would get an absolute magnitude of 1.45 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.45. Magnitude, whether it be apparent/visual or absolute magnitude is measured by a number, the smaller the number, the brighter the Star is. Our own Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.

Distance to Sirius

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 379.00 which gave the calculated distance to Sirius as 8.61 light years away from us or 2.64 parsecs. In 2007, Hipparcos data was revised with a new parallax of 379.00 which put Sirius at a distance of 8.61 light years or 2.64 parsecs.

Source of Information

The source of the information if it has a Hip I.D. is from Simbad, the Hipparcos data library based at the University at Strasbourg, France. Hipparcos was a E.S.A. satellite operation launched in 1989 for four years. The items in red are values that I've calculated so they could well be wrong. Information regarding Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Sirius Facts


Traditional NameSirius
Short Name9 CMa
Bayer DesignationAlpha Canis Majoris
Alternative Name(s)9 Canis Majoris
Hipparcos Library I.D.32349
Yale Bright Star Catalogue (HR) Id2491
Henry Draper Designation48915
ConstellationCanis Major
Celestial TypeStar
Absolute Magnitude1.45 / 1.45
Apparent Magnitude-1.44
Right Ascension (R.A.)06h 45m 09.25
Declination (Dec.)-16 d 42`47.3
1997 Distance379.00 Parallax (milliarcseconds)
 8.61 Light Years
 2.64 Parsecs
2007 Distance379.00 Parallax (milliarcseconds)
 8.61 Light Years
 2.64 Parsecs
Proper Motion Dec.-1223.00 ± 1.00 milliarcseconds/year
Proper Motion RA.-546.00 ± 2.00 milliarcseconds/year
B-V Index0.00
Spectral TypeA0m...
Brightest in Night Sky2nd
Colour(A) blue
Star Typeless luminous star
Companion StarsSirius B
Radius (x the Sun)1.51
Calculated Effective Temperature10,293 Kelvin

Location of Sirius in Canis Major


Sirius (Alpha Canis Majoris) Location in Canis Major

The map was generated using Night Vision, an awesome free application by Brian Simpson.



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