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Hadar (Beta Centauri) Star Facts

Hadar Facts

  • Hadar is a pulsating giant star that can be located in the constellation of Centaurus. The description is based on the spectral class.
  • Hadar is a main star of the constellation outline.
  • Based on the spectral type (B1III) of the star, the star's colour is blue .
  • Hadar is the 11th brightest star in the night sky and the 2nd brightest star in Centaurus 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.
  • Hadar has a radius that is 13.00 times bigger than the Suns. Radius
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 392.02 light years away from us. Distance

Hadar's Alternative Names

Beta Centauri (Bet Cen) 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 HR5267. HIP68702 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD122451.

Hadar has alternative name(s) :- Beta CenTau, Agena, bet Cen. In Arabic, it is known as Hadar.

The Gould star designation is one that was designed by American astronomer, Benjamin Apthorp Gould. Gould stars are predominantly in the Southern and Equatorial constellations but do appear in northern constellations such as Bootes and Orion. The star has the designation 304 G. Centauri. There are no stars with a Gould designation in Ursa Major for example.

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

Location of Hadar

The location of the giant 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 Hadar, the location is 14h 03m 49.44 and -60° 22` 22.7 .

Radial Velocity and Proper Motion of Hadar

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 -23.16 ± 0.34 milliarcseconds/year towards the north and -33.27 ± 0.50 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 5.90000 km/s with an error of about 3.80 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 Hadar

Hadar Temperature and Colour

Based on the star's spectral type of B1III , Hadar's colour and type is blue giant star. The star's effective temperature is 2,500 Kelvin which is cooler than our own Sun's effective Temperature which is 5,777 Kelvin

Hadar 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 45,273.90 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Hadar Radius

Hadar Radius has been calculated as being 13.00 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 9,045,400.00.km. If you need the diameter of the star, you just need to multiple the radius by 2.

Hadar Mass

The Hadar's solar mass is 10.07 times that of our star, the Sun. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

Hadar Apparent and Absolute Magnitudes

Hadar has an apparent magnitude of 0.61 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 -5.42 If you used the 2007 Parallax value, you would get an absolute magnitude of -4.79. 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 Hadar

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 6.21000 which gave the calculated distance to Hadar as 525.22 light years away from Earth or 161.03 parsecs. If you want that in miles, it is about 3,087,571,618,503,495.64, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 8.32000 which put Hadar at a distance of 392.02 light years or 120.19 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 24,790,794.32 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 7,321.00 Parsecs or 23,878.42 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 Hadar

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)
Walking465,723,782,725.15
Car1202,190,792,757.50
Airbus A380736357,194,471.33
Speed of Sound (Mach 1)767.269342,637,498.58
Concorde (Mach 2)1,534.54171,318,526.01
New Horizons Probe33,0007,966,519.12
Speed of Light670,616,629.00392.02

Variable Type of Hadar

The star is a pulsating Beta Cephei 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. Hadar brightness ranges from a magnitude of 0.556 to a magnitude of 0.516 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 days (variability).

Meteor Showers Radiating from near Hadar

The Beta Centaurids Meteor Shower radiants from a point near this star. The meteor shower runs typically between 2-Feb - 25 Feb with a peak date of Feb 8/9.

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 Hadar Facts and Figures

Visual Facts


Primary / Proper / Traditional NameHadar
Alternative NamesBeta Centauri, Bet Cen, Beta CenTau, Agena, Hadar, HD 122451, HIP 68702, HR 5267, 304 G. Centauri, bet Cen
Spectral TypeB1III
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeGiant Star
ColourBlue
GalaxyMilky Way
ConstellationCentaurus
Absolute Magnitude -5.42 / -4.79
Visual / Apparent Magnitude0.61
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)14h 03m 49.44
Declination (Dec.)-60° 22` 22.7
Galactic Latitude1.25113883 degrees
Galactic Longitude311.76704914 degrees
1997 Distance from Earth6.21000 Parallax (milliarcseconds)
 525.22 Light Years
 161.03 Parsecs
2007 Distance from Earth8.32000 Parallax (milliarcseconds)
 392.02 Light Years
 120.19 Parsecs
 24,790,794.32 Astronomical Units
Galacto-Centric Distance23,878.42 Light Years / 7,321.00 Parsecs
Proper Motion Dec.-23.16000 ± 0.34000 milliarcseconds/year
Proper Motion RA.-33.27000 ± 0.50000 milliarcseconds/year
B-V Index-0.23
Radial Velocity5.90000 ± 3.80 km/s
Eccentricity0.05570
Semi-Major Axis6949.0000000
Stellar Luminosity (Lsun)45273.9000000
Brightest in Night Sky11th

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeBeta Cephei
Mean Variability Period in Days0.030
Variable Magnitude Range (Brighter - Dimmer)0.516 - 0.556

Estimated Calculated Facts


Radius (x the Sun)13.00
Effective Temperature19,982 Kelvin
Mass Compared to the Sun10.07

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
122451-59 5365.4A0.90000-21.00000-23.00000B3Blue/White
B4.100001960

Location of Hadar in Centaurus


Hadar Location in Centaurus

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

Centaurus Main Stars


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