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Theta Muscae, HD113904, HIP64094, HR4952

Theta Muscae is a eclipsing binary system very luminous supergiant starWolf-Rayet star that can be located in the constellation of Musca. Theta Muscae is the brightest star in Musca 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.

Theta Muscae is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR4952. HIP64094 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD113904.

Theta Muscae has alternative name(s), the Mus.

Location of Theta Muscae

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 Theta Muscae, the location is 13h 08m 07.16 and -65d 18` 21.7 .

Wolf-Rayet Star

The star is a Wolf-Rayet, a rare type of star of which not many are known. These stars are extremely luminous and large compared to our Sun. They live fast and die hard in a matter of millions not billions of years like our Sun. They exhaust their hydrogen supplies, turning to other gasses and expand outwards with massive solar winds, moving a step closer in the stellar evolution towards their death in a super or hypernova explosion.

Proper Motion of Theta Muscae

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 -2.18 ± 0.34 miliarcseconds/year towards the north and -4.26 ± 0.48 miliarcseconds/year east if we saw them in the horizon. The Radial Velocity, that is the speed at which the star is moving away/towards us is -28.40000 km/s with an error of about 2.80 km/s .

Physical Properties (Temperature, Radius) of Theta Muscae

Theta Muscae has a spectral type of WC6 + O9.5I. This means the star is a Wolf-Rayet star. 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.

Theta Muscae Radius has been calculated as being 683.37 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 475,490,153.67.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 79.18. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Theta Muscae Apparent and Absolute Magnitudes

Theta Muscae has an apparent magnitude of 5.44 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 -12.17 If you used the 2007 Parallax value, you would get an absolute magnitude of -7.49. 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 Theta Muscae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.03 which gave the calculated distance to Theta Muscae as 108721.11 light years away from Earth or 33333.33 parsecs. It would take a spaceship travelling at the speed of light, 108721.11 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 0.26 which put Theta Muscae at a distance of 12544.74 light years or 3846.15 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 Theta Muscae

The star is a eclipsing binary system Eclipsing 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. Theta Muscae brightness ranges from a magnitude of 5.500 to a magnitude of 5.460 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 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 Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Theta Muscae Facts

Alternative Names

Short Namethe Mus
Bayer DesignationTheta Muscae
Hipparcos Library I.D.64094
Yale Bright Star Catalogue (HR) Id4952
Henry Draper Designation113904
Wolf-Rayet Id48

Visual Facts

Star Type Wolf-Rayet star
Absolute Magnitude-12.17 / -7.49
Visual / Apparent Magnitude5.44
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)13h 08m 07.16
Declination (Dec.)-65d 18` 21.7
Galactic Latitude-2.49 degrees
Galactic Longitude304.67 degrees
1997 Distance from Earth0.03 Parallax (milliarcseconds)
 108721.11 Light Years
 33333.33 Parsecs
2007 Revised Distance from Earth0.26 Parallax (milliarcseconds)
 12544.74 Light Years
 3846.15 Parsecs
Proper Motion Dec.-2.18 ± 0.34 milliarcseconds/year
Proper Motion RA.-4.26 ± 0.48 milliarcseconds/year
B-V Index-0.03
Radial Velocity-28.40 ± 2.80 km/s
Spectral TypeWC6 + O9.5I

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeEclipsing
Mean Variability Period in Days0.028
Variable Magnitude Range (Brighter - Dimmer)5.460 - 5.500

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
113904-64 2183.4A5.90000-7.00000-10.00000B0Blue/White

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