Universe Guide


Zuben Hakrabi, Eta Librae, 44 Librae, HD140417, HIP77060

Zuben Hakrabi (Eta Librae) is a blue subgiant star that can be located in the constellation of Libra. Zuben Hakrabi is the brightest star in Libra 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.

Eta Librae is the Bayer Classification for the star. HIP77060 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD140417.

Location of Zuben Hakrabi

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 Zuben Hakrabi, the location is 15h 44m 04.42 and -15d40`21.6 .

Proper Motion of Zuben Hakrabi

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 -64.28 ± 0.12 miliarcseconds/year towards the north and -34.72 ± 0.23 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Zuben Hakrabi

Zuben Hakrabi has a spectral type of A6IV. This means the star is a blue subgiant star. The star is 7361.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24008.8837518400000000s. The star has a B-V Colour Index of 0.23 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,593 Kelvin.

Zuben Hakrabi Radius has been calculated as being 2.01 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,401,328.71.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.04. 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 -0.01 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Zuben Hakrabi Apparent and Absolute Magnitudes

Zuben Hakrabi has an apparent magnitude of 5.41 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 2.14 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.11. 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 Zuben Hakrabi

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 22.21 which gave the calculated distance to Zuben Hakrabi as 146.85 light years away from Earth or 45.02 parsecs. It would take a spaceship travelling at the speed of light, 146.85 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 21.86 which put Zuben Hakrabi at a distance of 149.21 light years or 45.75 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 7,361.00 Parsecs or 24,008.88 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.

Zuben Hakrabi Facts

Alternative Names

Traditional/Proper NameZuben Hakrabi
Flamsteed Name44 Librae
Flamsteed Short Name44 Lib
Bayer DesignationEta Librae
Hipparcos Library I.D.77060
Bonner DurchmusterungBD-15 4171
Henry Draper Designation140417

Visual Facts

Star Typesubgiant star
Absolute Magnitude2.14 / 2.11
Visual / Apparent Magnitude5.41
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)15h 44m 04.42
Declination (Dec.)-15d40`21.6
Galactic Latitude30.13 degrees
Galactic Longitude352.52 degrees
1997 Distance from Earth22.21 Parallax (milliarcseconds)
 146.85 Light Years
 45.02 Parsecs
2007 Revised Distance from Earth21.86 Parallax (milliarcseconds)
 149.21 Light Years
 45.75 Parsecs
Galacto-Centric Distance24,008.88 Light Years / 7,361.00 Parsecs
Proper Motion Dec.-64.28 ± 0.12 milliarcseconds/year
Proper Motion RA.-34.72 ± 0.23 milliarcseconds/year
B-V Index0.23
Radial Velocity-31.20 ± 4.20 km/s
Iron Abundance-0.01 ± 9.99 Fe/H
Spectral TypeA6IV
Colour(A) blue

Estimated Facts

Calculated Effective Temperature7,593 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Zuben Hakrabi in Libra

Zuben Hakrabi (Eta Librae) Location in Libra

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

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