Universe Guide


Tien Kwan, Zeta Tauri, 123 Tauri, HD37202, HIP26451

Tien Kwan (Zeta Tauri) is a blue eclipsing binary system giant star that can be located in the constellation of Taurus. Tien Kwan is the brightest star in Taurus 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.

Zeta Tauri is the Bayer Classification for the star. HIP26451 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD37202.

Tien Kwan has alternative name(s), Zeta Tau , zet Tau.

Location of Tien Kwan

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 Tien Kwan, the location is 05h 37m 38.68 and +21d08`33.3 .

Proper Motion of Tien Kwan

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 -20.07 ± 0.50 miliarcseconds/year towards the north and 1.78 ± 0.82 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Tien Kwan

Tien Kwan has a spectral type of B4IIIp. This means the star is a blue giant star. The star is 7533.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24569.8847035200000000s. The star has a B-V Colour Index of -0.14 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 13,196 Kelvin.

Tien Kwan Radius has been calculated as being 5.81 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 4,041,367.54.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 6.20. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Tien Kwan Apparent and Absolute Magnitudes

Tien Kwan has an apparent magnitude of 2.97 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 -2.56 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.70. 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 Tien Kwan

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 7.82 which gave the calculated distance to Tien Kwan as 417.09 light years away from Earth or 127.88 parsecs. It would take a spaceship travelling at the speed of light, 417.09 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 7.33 which put Tien Kwan at a distance of 444.97 light years or 136.43 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.

The star's Galacto-Centric Distance is 7,533.00 Parsecs or 24,569.88 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Tien Kwan

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. This is a some uncertainty as to the type but the type mentioned is the current variable star classification for this star. Tien Kwan brightness ranges from a magnitude of 2.983 to a magnitude of 2.853 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.

Tien Kwan Facts

Alternative Names

Traditional/Proper NameTien Kwan
Flamsteed Name123 Tauri
Flamsteed Short Name123 Tau
Short Namezet Tau
Bayer DesignationZeta Tauri
Alternative Name(s)Zeta Tau
Hipparcos Library I.D.26451
Bonner DurchmusterungBD+21 908
Henry Draper Designation37202

Visual Facts

Star Typegiant star
Absolute Magnitude-2.56 / -2.70
Visual / Apparent Magnitude2.97
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)05h 37m 38.68
Declination (Dec.)+21d08`33.3
Galactic Latitude-5.64 degrees
Galactic Longitude185.69 degrees
1997 Distance from Earth7.82 Parallax (milliarcseconds)
 417.09 Light Years
 127.88 Parsecs
2007 Revised Distance from Earth7.33 Parallax (milliarcseconds)
 444.97 Light Years
 136.43 Parsecs
Galacto-Centric Distance24,569.88 Light Years / 7,533.00 Parsecs
Proper Motion Dec.-20.07 ± 0.50 milliarcseconds/year
Proper Motion RA.1.78 ± 0.82 milliarcseconds/year
B-V Index-0.14
Radial Velocity20.00 ± 2.50 km/s
Spectral TypeB4IIIp
Colour(B) blue

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeEclipsing probably
Mean Variability Period in Days0.126
Variable Magnitude Range (Brighter - Dimmer)2.853 - 2.983

Estimated Facts

Calculated Effective Temperature13,196 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Tien Kwan in Taurus

Tien Kwan (Zeta Tauri) Location in Taurus

The map was generated using Night Vision, an awesome free application by Brian Simpson.

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