Universe Guide

Tejat (Mu Geminorum, 13 Geminorum) Star Facts

Tejat Facts

Tejat's Alternative Names

Mu Geminorum (Mu. Gem) 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 HR2286. HIP30343 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD44478.

Tejat has alternative name(s) :- Tejat Posterior, mu. Gem.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 13 Geminorum. The Flamsteed name can be shortened to 13 Gem.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+22 1304.

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

Location of Tejat

The location of the giant 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 Tejat, the location is 06h 22m 57.59 and +22° 30` 49.9 .

Radial Velocity and Proper Motion of Tejat

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 -110.03 ± 0.45 milliarcseconds/year towards the north and 56.39 ± 0.71 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 54.38 km/s with an error of about 0.24 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 (Colour, Temperature) of Tejat

Tejat Colour and Temperature

Tejat has a spectral type of M3IIIvar. This means the star is a red giant star. The star has a B-V Colour Index of 1.62 which means the star's temperature is about 3,728 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu at being .

Tejat Radius

Radius has been calculated as being 42.46 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 29,542,664.96.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 42.46. 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 -0.03 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Tejat Apparent and Absolute Magnitudes

Tejat has an apparent magnitude of 2.87 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 -1.39 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.39. 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 Tejat

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 14.07 which gave the calculated distance to Tejat as 231.81 light years away from Earth or 71.07 parsecs. If you want that in miles, it is 155,455,640,768.

In 2007, Hipparcos data was revised with a new parallax of 14.08 which put Tejat at a distance of 231.65 light years or 71.02 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 14,648,824.47 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.

The star's Galacto-Centric Distance is 7,470.00 Parsecs or 24,364.40 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to Tejat

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 A380736211,071,116.99
Speed of Sound (Mach 1)767.269202,469,201.95
Concorde (Mach 2)1,534.54101,234,469.03
New Horizons Probe33,0004,707,525.52
Speed of Light670,616,629.00231.65

Variable Type of Tejat

The star is a pulsating Slow Irregular 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. Tejat brightness ranges from a magnitude of 2.993 to a magnitude of 2.873 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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.

Hide Explanations
Show GridLines

Additional Tejat Facts and Figures

Visual Facts

Primary / Proper / Traditional NameTejat
Alternative NamesMu Geminorum, Mu. Gem, Tejat Posterior, HD 44478, HIP 30343, HR 2286, 13 Geminorum, 13 Gem, BD+22 1304, mu. Gem
Spectral TypeM3IIIvar
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeGiant Star
GalaxyMilky Way
Absolute Magnitude -1.39 / -1.39
Visual / Apparent Magnitude2.87
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)06h 22m 57.59
Declination (Dec.)+22° 30` 49.9
Galactic Latitude4.17 degrees
Galactic Longitude189.73 degrees
1997 Distance from Earth14.07 Parallax (milliarcseconds)
 231.81 Light Years
 71.07 Parsecs
2007 Distance from Earth14.08 Parallax (milliarcseconds)
 231.65 Light Years
 71.02 Parsecs
 14,648,824.47 Astronomical Units
Galacto-Centric Distance24,364.40 Light Years / 7,470.00 Parsecs
Proper Motion Dec.-110.03 ± 0.45 milliarcseconds/year
Proper Motion RA.56.39 ± 0.71 milliarcseconds/year
B-V Index1.62
Radial Velocity54.38 ± 0.24 km/s
Iron Abundance-0.03 ± 9.99 Fe/H
Semi-Major Axis5534.00

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSlow Irregular
Mean Variability Period in Days0.106
Variable Magnitude Range (Brighter - Dimmer)2.873 - 2.993

Estimated Calculated Facts

Radius (x the Sun)42.46
Effective Temperature3,728 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
44478+22 1304.0A3.2000056.00000-112.00000M1Red

Gemini Main Stars

Comments and Questions

There's no register feature and no need to give an email address if you don't need to. All messages will be reviewed before being displayed. Comments may be merged or altered slightly such as if an email address is given in the main body of the comment.

You can decline to give a name which if that is the case, the comment will be attributed to a random star. A name is preferred even if its a random made up one by yourself.

This website is using cookies. More info. That's Fine