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Tau Canis Majoris, 30 Canis Majoris, HD57061, HIP35415

Tau Canis Majoris is a blue eclipsing binary system very luminous supergiant star that can be located in the constellation of CanisMajor. Tau Canis Majoris 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.

Tau Canis Majoris is the Bayer Classification for the star. HIP35415 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD57061.

Tau Canis Majoris has alternative name(s), tau CMa.

Location of Tau Canis Majoris

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 Tau Canis Majoris, the location is 07h 18m 42.49 and -24d57`15.8 .

Proper Motion of Tau Canis Majoris

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 5.02 ± 0.41 miliarcseconds/year towards the north and -2.31 ± 0.59 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Tau Canis Majoris

Tau Canis Majoris has a spectral type of O9Ib. This means the star is a blue supergiant star. The star has a B-V Colour Index of -0.13 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 15,544 Kelvin.

Tau Canis Majoris Radius has been calculated as being 16.90 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 11,757,558.14.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 15.77. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Tau Canis Majoris Apparent and Absolute Magnitudes

Tau Canis Majoris has an apparent magnitude of 4.37 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 -5.59 If you used the 2007 Parallax value, you would get an absolute magnitude of -5.44. 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 Tau Canis Majoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.02 which gave the calculated distance to Tau Canis Majoris as 3197.68 light years away from Earth or 980.39 parsecs. It would take a spaceship travelling at the speed of light, 3197.68 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 1.09 which put Tau Canis Majoris at a distance of 2992.32 light years or 917.43 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.

Variable Type of Tau Canis Majoris

The star is a eclipsing binary system W Ursae Majoris variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. Tau Canis Majoris brightness ranges from a magnitude of 4.372 to a magnitude of 4.320 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 1.3 days (variability).

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.

Tau Canis Majoris Facts

Alternative Names

Flamsteed Name30 Canis Majoris
Flamsteed Short Name30 CMa
Short Nametau CMa
Bayer DesignationTau Canis Majoris
Hipparcos Library I.D.35415
Henry Draper Designation57061

Visual Facts

Star Typesupergiant star
Absolute Magnitude-5.59 / -5.44
Visual / Apparent Magnitude4.37
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)07h 18m 42.49
Declination (Dec.)-24d57`15.8
Galactic Latitude-5.54 degrees
Galactic Longitude238.18 degrees
1997 Distance from Earth1.02 Parallax (milliarcseconds)
 3197.68 Light Years
 980.39 Parsecs
2007 Revised Distance from Earth1.09 Parallax (milliarcseconds)
 2992.32 Light Years
 917.43 Parsecs
Proper Motion Dec.5.02 ± 0.41 milliarcseconds/year
Proper Motion RA.-2.31 ± 0.59 milliarcseconds/year
B-V Index-0.13
Radial Velocity33.80 ± 1.80 km/s
Spectral TypeO9Ib
Colour(O) blue

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeW Ursae Majoris
Mean Variability Period in Days1.282
Variable Magnitude Range (Brighter - Dimmer)4.320 - 4.372

Estimated Facts

Calculated Effective Temperature15,544 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
57061-24 5176.2A4.40000-11.000006.00000OeBlue
-24 5180.2D8.800001834

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