Universe Guide

Theta Muscae (Wolf-Rayet Star) Facts

Theta Muscae Facts

  • Theta Muscae is a eclipsing binary sys wolf-rayet star that can be located in the constellation of Musca. The description is based on the spectral class.
  • Theta Muscae is not part of the constellation outline but is within the borders of the constellation.
  • The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 12544.74 light years away from us. Distance

Theta Muscae's Alternative Names

Theta Muscae (The Mus) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

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.

More details on objects' alternative names can be found at Star Names .

Location of Theta Muscae

The location of the wolf-rayet star in the night sky 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 object is compared to the celestial equator and is expressed in degrees. For Theta Muscae, the location is 13h 08m 07.16 and -65° 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.

Radial Velocity and Proper Motion of Theta Muscae

Proper Motion

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 milliarcseconds/year towards the north and -4.26 ± 0.48 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -28.40000 km/s with an error of about 2.80 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties of Theta Muscae

Theta Muscae Colour

Based on the star's spectral type of WC6 + O9.5I The star has a B-V Colour Index of -0.03 which means the star's temperature is about 11,122 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

Theta Muscae Radius

Theta Muscae estimated 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. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 79.179208782654856075524407902. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It 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 0.03000 which gave the calculated distance to Theta Muscae as 108721.11 light years away from Earth or 33333.33 parsecs. If you want that in miles, it is about 639,130,675,846,686,313.01, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 0.26000 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.

Using the 2007 distance, the star is roughly 793,319,856.62 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun.

Travel Time to Theta Muscae

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A38073611,430,314,199.02
Speed of Sound (Mach 1)767.26910,964,487,357.73
Concorde (Mach 2)1,534.545,482,236,533.74
New Horizons Probe33,000254,930,643.95
Speed of Light670,616,629.0012,544.74

Variable Type of Theta Muscae

The star is a eclipsing binary sys 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.

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Additional Theta Muscae Facts and Figures

Visual Facts

Primary / Proper / Traditional NameTheta Muscae
Alternative NamesThe Mus, HD 113904, HIP 64094, HR 4952, the Mus, WR 48
Spectral TypeWC6 + O9.5I
Constellation's Main StarNo
Multiple Star SystemYes
Star Type very luminous Supergiant StarWolf-Rayet star
GalaxyMilky Way
Absolute Magnitude -12.17 / -7.49
Visual / Apparent Magnitude5.44
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)13h 08m 07.16
Declination (Dec.)-65° 18` 21.7
Galactic Latitude-2.49072535 degrees
Galactic Longitude304.67455010 degrees
1997 Distance from Earth0.03000 Parallax (milliarcseconds)
 108721.11 Light Years
 33333.33 Parsecs
2007 Distance from Earth0.26000 Parallax (milliarcseconds)
 12544.74 Light Years
 3846.15 Parsecs
 793,319,856.62 Astronomical Units
Proper Motion Dec.-2.18000 ± 0.34000 milliarcseconds/year
Proper Motion RA.-4.26000 ± 0.48000 milliarcseconds/year
B-V Index-0.03
Radial Velocity-28.40000 ± 2.80 km/s

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

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

Estimated Calculated Facts

Radius (x the Sun)79.18
Effective Temperature11,122 Kelvin

Sources and Links

SIMBAD SourceLink

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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