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Zeta1 Librae, 32 Librae, HD137744, HIP75730, HR5743

Zeta1 Librae is a orange to red giant star that can be located in the constellation of Libra. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Zeta1 Librae's Alternative Names

(Zeta1 Librae) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR5743. HIP75730 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD137744.

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 32 Librae with it shortened to 32 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-16 4089.

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

Location of Zeta1 Librae

The location of the 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 star is compared to the celestial equator and is expressed in degrees. For Zeta1 Librae, the location is 15h 28m 15.40 and -16° 42` 59.1 .

Proper Motion of Zeta1 Librae

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 -34.60 ± 0.28 miliarcseconds/year towards the north and 16.30 ± 0.43 miliarcseconds/year east if we saw them in the horizon. The Radial Velocity, that is the speed at which the star is moving away/towards us is -21.40000 km/s with an error of about 2.90 km/s .

Zeta1 Librae 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 865.26 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 Zeta1 Librae

Zeta1 Librae has a spectral type of K4III. This means the star is a orange to red giant star. The star is 7,204.00 Parsecs from the Galactic Centre or terms of Light Years is 23,496.81 s. The star has a B-V Colour Index of 1.54 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,913 Kelvin.

Zeta1 Librae Radius has been calculated as being 42.06 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 29,267,366.51.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 36.30. 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 -0.15 with an error value of 0.06 Fe/H with the Sun has a value of 1 to put it into context.

Zeta1 Librae Apparent and Absolute Magnitudes

Zeta1 Librae has an apparent magnitude of 5.64 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 -1.58 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.26. 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 Zeta1 Librae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.59 which gave the calculated distance to Zeta1 Librae as 908.53 light years away from Earth or 278.55 parsecs. It would take a spaceship travelling at the speed of light, 908.53 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 4.16 which put Zeta1 Librae at a distance of 784.05 light years or 240.38 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 7,204.00 Parsecs or 23,496.81 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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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Zeta1 Librae Facts

Visual Facts


Primary / Proper / Traditional NameZeta1 Librae
Alternative NamesHD 137744, HIP 75730, HR 5743, 32 Librae, 32 Lib, BD-16 4089
Spectral TypeK4III
Multiple Star SystemYes
Star TypeGiant Star
Colour orange to red
GalaxyMilky Way
ConstellationLibra
Absolute Magnitude-1.58 / -1.26
Visual / Apparent Magnitude5.64
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)15h 28m 15.40
Declination (Dec.)-16° 42` 59.1
Galactic Latitude31.96 degrees
Galactic Longitude348.46 degrees
1997 Distance from Earth3.59 Parallax (milliarcseconds)
 908.53 Light Years
 278.55 Parsecs
2007 Distance from Earth4.16 Parallax (milliarcseconds)
 784.05 Light Years
 240.38 Parsecs
Galacto-Centric Distance23,496.81 Light Years / 7,204.00 Parsecs
Proper Motion Dec.-34.60 ± 0.28 milliarcseconds/year
Proper Motion RA.16.30 ± 0.43 milliarcseconds/year
B-V Index1.54
Radial Velocity-21.40 ± 2.90 km/s
Iron Abundance-0.15 ± 0.06 Fe/H
Eccentricity0.08
Semi-Major Axis7429.00
Stellar Luminosity (Lsun)865.26
Associated / Clustered StarsZeta3 Librae
Zeta4 Librae

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature3,913 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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