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Lambda Tauri (35 Tauri) Star Facts

Lambda Tauri Facts

Lambda Tauri's Alternative Names

Lambda Tauri (Lam Tau) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in the early nineteenth century. The brightest star in the constellation is normally given the Alpha designation although there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR1239. HIP18724 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD25204.

Lambda Tauri has alternative name(s) :- , lam Tau.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 35 Tauri with it shortened to 35 Tau.

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+12 539.

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

Location of Lambda Tauri

The location of the main sequence 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 Lambda Tauri, the location is 04h 00m 40.82 and +12° 29` 25.4 .

Radial Velocity and Proper Motion of Lambda Tauri

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 -14.42 ± 0.07 milliarcseconds/year towards the north and -8.02 ± 0.17 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 13.40 km/s with an error of about 4.00 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.

Lambda Tauri 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 1,430.93 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of Lambda Tauri

Lambda Tauri Colour and Temperature

Lambda Tauri has a spectral type of B3V + A. This means the star is a blue main sequence star. The star has a B-V Colour Index of -0.09 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 11,375 Kelvin.

Lambda Tauri Radius

Radius has been calculated as being 5.69 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,958,251.44.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 7.43. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Lambda Tauri Apparent and Absolute Magnitudes

Lambda Tauri has an apparent magnitude of 3.41 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 -1.87 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.45. 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 Lambda Tauri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 8.81 which gave the calculated distance to Lambda Tauri as 370.22 light years away from Earth or 113.51 parsecs. It would take a spaceship travelling at the speed of light, 370.22 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 6.74 which put Lambda Tauri at a distance of 483.92 light years or 148.37 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 30,603,296.06 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 7,529.00 Parsecs or 24,556.84 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 Lambda Tauri

The star is a eclipsing Beta Persei (Algol)/ 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. Lambda Tauri brightness ranges from a magnitude of 3.500 to a magnitude of 3.340 over its variable period. The smaller the magnitude, the brighter the star.

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 Lambda Tauri Facts and Figures

Visual Facts


Primary / Proper / Traditional NameLambda Tauri
Alternative NamesLam Tau, HD 25204, HIP 18724, HR 1239, 35 Tauri, 35 Tau, BD+12 539, lam Tau
Spectral TypeB3V + A
Constellation's Main StarYes
Multiple Star SystemNo / Unknown
Star Type Main Sequence Dwarf Star
ColourBlue
GalaxyMilky Way
ConstellationTaurus
Absolute Magnitude -1.87 / -2.45
Visual / Apparent Magnitude3.41
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)04h 00m 40.82
Declination (Dec.)+12° 29` 25.4
Galactic Latitude-29.38 degrees
Galactic Longitude178.37 degrees
1997 Distance from Earth8.81 Parallax (milliarcseconds)
 370.22 Light Years
 113.51 Parsecs
2007 Distance from Earth6.74 Parallax (milliarcseconds)
 483.92 Light Years
 148.37 Parsecs
 30,603,296.06 Astronomical Units
Galacto-Centric Distance24,556.84 Light Years / 7,529.00 Parsecs
Proper Motion Dec.-14.42 ± 0.07 milliarcseconds/year
Proper Motion RA.-8.02 ± 0.17 milliarcseconds/year
B-V Index-0.09
Radial Velocity13.40 ± 4.00 km/s
Eccentricity0.15
Semi-Major Axis8695.00
Stellar Luminosity (Lsun)1,430.93

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing
Variable Star TypeBeta Persei (Algol)/
Variable Magnitude Range (Brighter - Dimmer)3.340 - 3.500

Estimated Calculated Facts


Radius (x the Sun)7.43
Effective Temperature11,375 Kelvin

Sources and Links


SIMBAD SourceLink

Taurus Main Stars


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