Universe Guide


Zubenelegenbi B, Alpha Librae B, 9 Librae, HD130841, HIP72622, HR5531

Zubenelegenbi B (Alpha Librae B) is a blue subgiant star that can be located in the constellation of Libra. Zubenelegenbi B 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.

Alpha Librae B is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR5531. HIP72622 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD130841. The Gliese ID of the star is Gliese GL564.1. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Ref : Star Names.

Location of Zubenelegenbi B

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 Zubenelegenbi B, the location is 14h 50m 52.78 and -16d02`29.8 .

Proper Motion of Zubenelegenbi B

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 -68.40 ± 0.11 miliarcseconds/year towards the north and -105.68 ± 0.19 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Zubenelegenbi B

Zubenelegenbi B has a spectral type of A3IV. This means the star is a blue subgiant star. The star is 7383.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24080.6396875200000000s. 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 8,153 Kelvin.

Zubenelegenbi B Radius has been calculated as being 3.12 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,171,422.36.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 3.06. 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 0.10 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

The star has a companion star which is in orbit close by, it has at least the following companions in close orbit, .

Zubenelegenbi B Apparent and Absolute Magnitudes

Zubenelegenbi B has an apparent magnitude of 2.75 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 0.88 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.92. 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 Zubenelegenbi B

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 42.25 which gave the calculated distance to Zubenelegenbi B as 77.20 light years away from Earth or 23.67 parsecs. It would take a spaceship travelling at the speed of light, 77.20 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 43.03 which put Zubenelegenbi B at a distance of 75.80 light years or 23.24 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 7,383.00 Parsecs or 24,080.64 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.

Zubenelegenbi B Facts

Alternative Names

Traditional/Proper NameZubenelegenbi B
Flamsteed Name9 Librae
Flamsteed Short Name9 Lib
Bayer DesignationAlpha Librae B
Hipparcos Library I.D.72622
Yale Bright Star Catalogue (HR) Id5531
Bonner DurchmusterungBD-15 3966
Gliese ID564.1
Henry Draper Designation130841

Visual Facts

Star Typesubgiant star
Absolute Magnitude0.88 / 0.92
Visual / Apparent Magnitude2.75
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)14h 50m 52.78
Declination (Dec.)-16d02`29.8
Galactic Latitude38.01 degrees
Galactic Longitude340.33 degrees
1997 Distance from Earth42.25 Parallax (milliarcseconds)
 77.20 Light Years
 23.67 Parsecs
2007 Revised Distance from Earth43.03 Parallax (milliarcseconds)
 75.80 Light Years
 23.24 Parsecs
Galacto-Centric Distance24,080.64 Light Years / 7,383.00 Parsecs
Proper Motion Dec.-68.40 ± 0.11 milliarcseconds/year
Proper Motion RA.-105.68 ± 0.19 milliarcseconds/year
B-V Index0.14
Radial Velocity-22.00 ± 5.80 km/s
Iron Abundance0.10 ± 9.99 Fe/H
Spectral TypeA3IV
Colour(A) blue

Estimated Facts

Calculated Effective Temperature8,153 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Zubenelegenbi B in Libra

Zubenelegenbi B (Alpha Librae B) Location in Libra

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

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