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HD 136905

HD 136905 Facts

  • HD 136905 is a eclipsing binary sys variable star that can be located in the constellation of Libra. The description is based on the spectral class.
  • HD 136905 is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (K0) of the star, the star's colour is orange to red .
  • The star can not be seen by the naked eye, you need a telescope to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 378.38 light years away from us. Distance

HD 136905's Alternative Names

HIP75325 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD136905.

HD 136905 has alternative name(s) :- GX Lib, GX Lib.

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-06 4193.

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

Location of HD 136905

The location of the variable 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 HD 136905, the location is 15h 23m 26.06 and -06° 36` 36.7 .

Radial Velocity and Proper Motion of HD 136905

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 -122.17 ± 0.31 milliarcseconds/year towards the north and -0.66 ± 0.53 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 61.28000 km/s with an error of about 0.35 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 HD 136905

HD 136905 Temperature and Colour

Based on the star's spectral type of K0 , HD 136905's colour and type is orange to red variable star. The star has a B-V Colour Index of 1.05 which means the star's temperature is about 4,866 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

HD 136905 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 20.69 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

HD 136905 Radius

HD 136905 estimated radius has been calculated as being 4.35 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,027,053.24.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 5.3032225913807742390343457878. 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.

HD 136905 Apparent and Absolute Magnitudes

HD 136905 has an apparent magnitude of 7.29 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 2.40 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.97. 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 HD 136905

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 10.51000 which gave the calculated distance to HD 136905 as 310.34 light years away from Earth or 95.15 parsecs. If you want that in miles, it is about 1,824,372,598,313,801.53, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 8.62000 which put HD 136905 at a distance of 378.38 light years or 116.01 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 23,928,613.44 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 7,312.00 Parsecs or 23,849.06 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 HD 136905

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)
Walking463,436,980,020.26
Car1202,114,566,000.68
Airbus A380736344,766,195.76
Speed of Sound (Mach 1)767.269330,715,720.41
Concorde (Mach 2)1,534.54165,357,644.69
New Horizons Probe33,0007,689,330.91
Speed of Light670,616,629.00378.38

Variable Type of HD 136905

The star is a eclipsing binary sys RS Canum Venaticorum 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. HD 136905 brightness ranges from a magnitude of 7.633 to a magnitude of 7.429 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 11.1 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.

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Additional HD 136905 Facts and Figures

Visual Facts


Primary / Proper / Traditional NameHD 136905
Alternative NamesGX Lib, HD 136905, HIP 75325, BD-06 4193, GX Lib
Spectral TypeK0
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
ColourOrange to Red
GalaxyMilky Way
ConstellationLibra
Absolute Magnitude 2.40 / 1.97
Visual / Apparent Magnitude7.29
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)15h 23m 26.06
Declination (Dec.)-06° 36` 36.7
Galactic Latitude40.10396723 degrees
Galactic Longitude356.01896468 degrees
1997 Distance from Earth10.51000 Parallax (milliarcseconds)
 310.34 Light Years
 95.15 Parsecs
2007 Distance from Earth8.62000 Parallax (milliarcseconds)
 378.38 Light Years
 116.01 Parsecs
 23,928,613.44 Astronomical Units
Galacto-Centric Distance23,849.06 Light Years / 7,312.00 Parsecs
Proper Motion Dec.-122.17000 ± 0.31000 milliarcseconds/year
Proper Motion RA.-0.66000 ± 0.53000 milliarcseconds/year
B-V Index1.05
Radial Velocity61.28000 ± 0.35 km/s
Eccentricity0.47700
Semi-Major Axis5487.0000000
Stellar Luminosity (Lsun)20.6900000

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing binary sys
Variable Star TypeRS Canum Venaticorum
Mean Variability Period in Days11.125
Variable Magnitude Range (Brighter - Dimmer)7.429 - 7.633

Estimated Calculated Facts


Radius (x the Sun)5.30
Effective Temperature4,866 Kelvin

Sources and Links


SIMBAD SourceLink

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