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Delta Librae (19 Librae) Star Facts

Delta Librae Facts

Delta Librae's Alternative Names

Delta Librae (Del Lib) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR5586. HIP73473 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD132742.

Delta Librae has alternative name(s) :- , del Lib.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 19 Librae. The Flamsteed name can be shortened to 19 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-07 3938.

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

Location of Delta Librae

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 Delta Librae, the location is 15h 00m 58.39 and -08° 31` 08.2 .

Radial Velocity and Proper Motion of Delta Librae

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 -4.76 ± 0.34 milliarcseconds/year towards the north and -63.46 ± 0.60 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 -40.00 km/s with an error of about 4.20 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.

Delta 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 86.21 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 Delta Librae

Delta Librae Colour and Temperature

Delta Librae has a spectral type of B9.5V. This means the star is a blue main sequence star. The star has a B-V Colour Index of 0 which means the star's temperature is about 9,531 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu at being .

Delta Librae Radius

Radius has been calculated as being 3.33 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,317,983.30.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 3.21. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Delta Librae Apparent and Absolute Magnitudes

Delta Librae has an apparent magnitude of 4.91 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 0.06 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.14. 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 Delta Librae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 10.72 which gave the calculated distance to Delta Librae as 304.26 light years away from Earth or 93.28 parsecs. If you want that in miles, it is 204,041,815,540.

In 2007, Hipparcos data was revised with a new parallax of 11.11 which put Delta Librae at a distance of 293.58 light years or 90.01 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 18,565,765.84 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 7,335.00 Parsecs or 23,924.08 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 Delta Librae

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)
Walking449,219,907,485.46
Car1201,640,663,582.85
Airbus A380736267,499,497.20
Speed of Sound (Mach 1)767.269256,597,920.60
Concorde (Mach 2)1,534.54128,298,793.09
New Horizons Probe33,0005,966,049.39
Speed of Light670,616,629.00293.58

Variable Type of Delta Librae

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. Delta Librae brightness ranges from a magnitude of 5.933 to a magnitude of 4.924 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 2.3 days (variability).

Meteor Showers Radiating from near Delta Librae

The delta Librids Meteor Shower radiants from a point near this star. The meteor shower runs typically between with a peak date of 14th August. The speed of a meteor in the shower is 7 Km/s.

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 Delta Librae Facts and Figures

Visual Facts


Primary / Proper / Traditional NameDelta Librae
Alternative NamesDel Lib, HD 132742, HIP 73473, HR 5586, 19 Librae, 19 Lib, BD-07 3938, del Lib
Spectral TypeB9.5V
Constellation's Main StarNo
Multiple Star SystemYes
Star Type Main Sequence Dwarf Star
ColourBlue
GalaxyMilky Way
ConstellationLibra
Absolute Magnitude 0.06 / 0.14
Visual / Apparent Magnitude4.91
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)15h 00m 58.39
Declination (Dec.)-08° 31` 08.2
Galactic Latitude42.51 degrees
Galactic Longitude348.87 degrees
1997 Distance from Earth10.72 Parallax (milliarcseconds)
 304.26 Light Years
 93.28 Parsecs
2007 Distance from Earth11.11 Parallax (milliarcseconds)
 293.58 Light Years
 90.01 Parsecs
 18,565,765.84 Astronomical Units
Galacto-Centric Distance23,924.08 Light Years / 7,335.00 Parsecs
Proper Motion Dec.-4.76 ± 0.34 milliarcseconds/year
Proper Motion RA.-63.46 ± 0.60 milliarcseconds/year
B-V Index0.00
Radial Velocity-40.00 ± 4.20 km/s
Eccentricity0.14
Semi-Major Axis7390.00
Stellar Luminosity (Lsun)86.21

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing
Variable Star TypeBeta Persei (Algol)/
Mean Variability Period in Days2.327
Variable Magnitude Range (Brighter - Dimmer)4.924 - 5.933

Estimated Calculated Facts


Radius (x the Sun)3.21
Effective Temperature9,531 Kelvin

Sources and Links


SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
132742-07 3938.0A-66.00000-9.00000A0White
B12.100001950
C11.300001950
CD13.700001950

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