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Omicron Centauri, HD100261, HIP56243, HR4441

Omicron Centauri is a white to yellow pulsating very luminous supergiant star that can be located in the constellation of Centaurus. Omicron Centauri is the 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.

Omicron Centauri is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR4441. HIP56243 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD100261. The Id of the star in the Gould Star Catalogue is 37. Stars in the southern hemisphere are more likely to have a Gould Id than the northern hemisphere. For example, there are no Gould classified stars in Ursa Major.

Omicron Centauri has alternative name(s), Omicron CenTau , omi01 Cen.

Location of Omicron Centauri

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 Omicron Centauri, the location is 11h 31m 46.07 and -59d 26` 31.4 .

Proper Motion of Omicron Centauri

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 1.72 ± 0.24 miliarcseconds/year towards the north and -4.31 ± 0.32 miliarcseconds/year east if we saw them in the horizon.

Omicron Centauri 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 9600.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of Omicron Centauri

Omicron Centauri has a spectral type of G0Ia. This means the star is a white to yellow supergiant star. The star has a B-V Colour Index of 1.02 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,929 Kelvin.

Omicron Centauri Radius has been calculated as being 122.87 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 85,490,606.47.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 217.49. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Omicron Centauri Apparent and Absolute Magnitudes

Omicron Centauri has an apparent magnitude of 5.07 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 -4.91 If you used the 2007 Parallax value, you would get an absolute magnitude of -6.15. 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 Omicron Centauri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.01 which gave the calculated distance to Omicron Centauri as 3229.34 light years away from Earth or 990.10 parsecs. It would take a spaceship travelling at the speed of light, 3229.34 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 0.57 which put Omicron Centauri at a distance of 5722.16 light years or 1754.39 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.

Variable Type of Omicron Centauri

The star is a pulsating Semiregular giants and supergiants of F, G, or K spectral s, sometimes with emission lines in their spectral 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. Omicron Centauri brightness ranges from a magnitude of 5.349 to a magnitude of 5.146 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 days (variability).

Meteor Showers Radiating from near Omicron Centauri

The Omicron Centaurids Meteor Shower radiants from a point near this star. The meteor shower runs typically between Jan 31 - Feb 19 with a peak date of Feb 11. The speed of a meteor in the shower is 51 Km/s. The amount of meteors predicted to be seen per hour (Zenith Hourly Rate) is 51.

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.

Omicron Centauri Facts

Alternative Names

Short Nameomi01 Cen
Bayer DesignationOmicron Centauri
Alternative Name(s)Omicron CenTau
Hipparcos Library I.D.56243
Yale Bright Star Catalogue (HR) Id4441
Gould I.D.37
Henry Draper Designation100261

Visual Facts

Star Typesupergiant star
Absolute Magnitude-4.91 / -6.15
Visual / Apparent Magnitude5.07
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)11h 31m 46.07
Declination (Dec.)-59d 26` 31.4
Galactic Latitude1.88 degrees
Galactic Longitude292.95 degrees
1997 Distance from Earth1.01 Parallax (milliarcseconds)
 3229.34 Light Years
 990.10 Parsecs
2007 Revised Distance from Earth0.57 Parallax (milliarcseconds)
 5722.16 Light Years
 1754.39 Parsecs
Proper Motion Dec.1.72 ± 0.24 milliarcseconds/year
Proper Motion RA.-4.31 ± 0.32 milliarcseconds/year
B-V Index1.02
Radial Velocity-20.80 ± 0.60 km/s
Spectral TypeG0Ia
Associated / Clustered StarsOmicron2 Centauri
Colour(G) White to Yellow

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular giants and supergiants of F, G, or K spectral s, sometimes with emission lines in their spectral
Mean Variability Period in Days0.163
Variable Magnitude Range (Brighter - Dimmer)5.146 - 5.349

Estimated Facts

Luminosity (x the Sun)9,600.0000000
Calculated Effective Temperature4,929 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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
100261-58 3692.4A5.00000-3.00000-10.00000G4Yellow

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