Universe Guide

HomeFactsConstellationsCanis Major

Sirius, Alpha Canis Majoris, 9 Canis Majoris, HD48915, HIP32349, HR2491

Sirius (Alpha Canis Majoris) is a blue star that can be located in the constellation of CanisMajor. Sirius is the 2nd brightest star in the night sky and is the brightest star in Canis Major based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

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. The Gliese ID of the star is Gliese GL244A. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Ref : Star Names.

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 along the celestial equator. If the R.A. is positive then its eastwards. The Declination is how far north or south the star is compared to the celestial equator and is expressed in degrees. For Sirius, the location is 06h 45m 09.25 and -16d42`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 -1,223.07 ± 1.04 miliarcseconds/year towards the north and -546.01 ± 1.58 miliarcseconds/year 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 star. The star is 7402.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24142.6107228800000000s. The star has a B-V Colour Index of -0.03 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 11,122 Kelvin.

Sirius Radius has been calculated as being 1.29 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 897,444.94.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.29. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is 0.36 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

The star has a companion star which is in orbit close by, it has at least the following companions in close orbit, .

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 379.21 which gave the calculated distance to Sirius as 8.60 light years away from Earth or 2.64 parsecs. It would take a spaceship travelling at the speed of light, 8.60 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

In 2007, Hipparcos data was revised with a new parallax of 379.21 which put Sirius at a distance of 8.60 light years or 2.64 parsecs. It should not be taken as though the star is moving closer or further away from us. It is purely that the distance was recalculated.

The star's Galacto-Centric Distance is 7,402.00 Parsecs or 24,142.61 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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 Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Sirius Facts

Alternative Names

Traditional/Proper NameSirius
Flamsteed Name9 Canis Majoris
Flamsteed Short Name9 CMa
Bayer DesignationAlpha Canis Majoris
Hipparcos Library I.D.32349
Yale Bright Star Catalogue (HR) Id2491
Bonner DurchmusterungBD-16 1591
Gliese ID244A
Henry Draper Designation48915

Visual Facts

Star Type star
Absolute Magnitude1.45 / 1.45
Visual / Apparent Magnitude-1.44
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)06h 45m 09.25
Declination (Dec.)-16d42`47.3
Galactic Latitude-8.89 degrees
Galactic Longitude227.23 degrees
1997 Distance from Earth379.21 Parallax (milliarcseconds)
 8.60 Light Years
 2.64 Parsecs
2007 Revised Distance from Earth379.21 Parallax (milliarcseconds)
 8.60 Light Years
 2.64 Parsecs
Galacto-Centric Distance24,142.61 Light Years / 7,402.00 Parsecs
Proper Motion Dec.-1223.07 ± 1.04 milliarcseconds/year
Proper Motion RA.-546.01 ± 1.58 milliarcseconds/year
B-V Index-0.03
Radial Velocity-5.50 ± 0.40 km/s
Iron Abundance0.36 ± 9.99 Fe/H
Eccentricity0.59
Inclination136.53
Semi-Major Axis2490.40
Orbital Period (Days)18295.40
Argument Of Periastron327.27
Spectral TypeA0m...
Brightest in Night Sky2nd
Colour(A) blue

Estimated Facts

Calculated Effective Temperature11,122 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
48915-16 1591.0A-1.60000-553.00000-1205.00000A0White
B8.50000-553.00000-1205.00000A7White1862
BC-553.00000-1205.000001929
D14.00000A0White1915

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.


Add a Comment


Name:
Email: (Optional)
Comment: