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Mahasim (Theta Aurigae) - HD40312 - HIP28380

Mahasim (Theta Aurigae) is a blue rotating star that can be located in the constellation of Auriga. Theta Aurigae is the Bayer Classification for the star. HIP28380 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD40312. Mahasim has alternative name(s), 37 Aurigae , the_Aur, 37 Aur.

Location of Mahasim

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 Mahasim, the location is 05h 59m 43.24 and +37d12`46.0 .

Proper Motion of Mahasim

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 -073.79 ± 000.08 towards the north and 043.63 ± 000.16 east if we saw them in the horizon.

Mahasim Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 50600.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of Mahasim

Mahasim has a spectral type of A0p Si. This means the star is a blue star. The star has a B-V Colour Index of -0.08 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 12,939 Kelvin.

Mahasim has been calculated as 2.92 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,030,467.42.km.

Mahasim Apparent and Absolute Magnitudes

Mahasim has an apparent magnitude of 2.65 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 -0.98 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.88. 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 Mahasim

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 18.83 which gave the calculated distance to Mahasim as 173.21 light years away from Earth or 53.11 parsecs. It would take a spaceship travelling at the speed of light, 173.21 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 19.70 which put Mahasim at a distance of 165.57 light years or 50.76 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 Mahasim

The star is a rotating Alpha2 Canum Venaticorum 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. Mahasim brightness ranges from a magnitude of 3.000 to a magnitude of 3.000 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 4.0 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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Mahasim Facts

Alternative Names

Traditional NameMahasim
Short Namethe Aur, 37 Aur
Bayer DesignationTheta Aurigae
Alternative Name(s)37 Aurigae
Hipparcos Library I.D.28380
Bonner DurchmusterungBD+37 1380
Henry Draper Designation40312

Visual Facts

Star Type star
Absolute Magnitude-0.98 / -0.88
Apparent Magnitude2.65
Right Ascension (R.A.)05h 59m 43.24
Declination (Dec.)+37d12`46.0
1997 Distance from Earth18.83 Parallax (milliarcseconds)
 173.21 Light Years
 53.11 Parsecs
2007 Revised Distance from Earth19.70 Parallax (milliarcseconds)
 165.57 Light Years
 50.76 Parsecs
Proper Motion Dec.-73.79 ± 0.08 milliarcseconds/year
Proper Motion RA.43.63 ± 0.16 milliarcseconds/year
B-V Index-0.08
Spectral TypeA0p Si
Colour(A) blue

Variable Star Details

Variable Star ClassRotating
Variable Star TypeAlpha2 Canum Venaticorum
Mean Variability Period in Days4.000

Estimated Facts

Radius (x the Sun)2.92
Luminosity (x the Sun)50,600.0000000
Calculated Effective Temperature12,939 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
40312+37 1380.0A2.7000047.00000-80.00000A0White
B7.200001955
C10.700001939
+37 1379.0D9.20000-2.000001.000001924

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