Universe Guide

Omicron Centauri

Omicron Centauri Facts

  • Omicron Centauri is a pulsating supergiant star that can be located in the constellation of Centaurus. The description is based on the spectral class.
  • Omicron Centauri is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (G0Ia) of the star, the star's colour is yellow .
  • The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 5722.16 light years away from us. Distance

Omicron Centauri's Alternative Names

Omicron Centauri (Omi01 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 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.

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

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 37 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 Omicron Centauri

The location of the supergiant 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 Omicron Centauri, the location is 11h 31m 46.07 and -59° 26` 31.4 .

Radial Velocity and Proper Motion of Omicron Centauri

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 1.72 ± 0.24 milliarcseconds/year towards the north and -4.31 ± 0.32 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 -20.80 km/s with an error of about 0.60 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 Omicron Centauri

Omicron Centauri Temperature and Colour

Based on the star's spectral type of G0Ia , Omicron Centauri's colour and type is yellow supergiant star. The star has a B-V Colour Index of 1.02 which means the star's temperature is about 4,929 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

Omicron Centauri Radius

Omicron Centauri estimated 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. 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 217.49. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It 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. If you want that in miles, it is about 18,984,080,062,636,759.12, based on 1 Ly = 5,878,625,373,183.61 miles.

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.

Using the 2007 distance, the star is roughly 361,866,391.91 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.

Travel Time to Omicron Centauri

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)
Airbus A3807365,213,825,611.14
Speed of Sound (Mach 1)767.2695,001,343,270.48
Concorde (Mach 2)1,534.542,500,668,376.06
New Horizons Probe33,000116,284,110.60
Speed of Light670,616,629.005,722.16

Variable Type of Omicron Centauri

The star is a pulsating Semiregular giants 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.

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Additional Omicron Centauri Facts and Figures

Visual Facts

Primary / Proper / Traditional NameOmicron Centauri
Alternative NamesOmi01 Cen, Omicron CenTau, HD 100261, HIP 56243, HR 4441, 37 G. Centauri, omi01 Cen
Spectral TypeG0Ia
Constellation's Main StarNo
Multiple Star SystemYes
Star Type very luminous Supergiant Star
GalaxyMilky Way
Absolute Magnitude -4.91 / -6.15
Visual / Apparent Magnitude5.07
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)11h 31m 46.07
Declination (Dec.)-59° 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 Distance from Earth0.57 Parallax (milliarcseconds)
 5722.16 Light Years
 1754.39 Parsecs
  361,866,391.91 Astronomical Units
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
Associated / Clustered StarsOmicron2 Centauri

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular giants
Mean Variability Period in Days0.163
Variable Magnitude Range (Brighter - Dimmer)5.146 - 5.349

Estimated Calculated Facts

Radius (x the Sun)217.49
Effective Temperature4,929 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
100261-58 3692.4A5.00000-3.00000-10.00000G4Yellow

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