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Omicron2 Centauri, HD100262, HIP56250

Omicron2 Centauri is a blue pulsating very luminous supergiant star that can be located in the constellation of Centaurus. Omicron2 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.

Omicron2 Centauri is the Bayer Classification for the star. HIP56250 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD100262. The Id of the star in the Gould Star Catalogue is 38. 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.

Omicron2 Centauri has alternative name(s), omi02 Cen.

Location of Omicron2 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 Omicron2 Centauri, the location is 11h 31m 48.81 and -59d30`56.3 .

Proper Motion of Omicron2 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 1.12 ± 0.20 miliarcseconds/year towards the north and -6.89 ± 0.28 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Omicron2 Centauri

Omicron2 Centauri has a spectral type of A3Ia. This means the star is a blue supergiant star. The star has a B-V Colour Index of 0.43 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,305 Kelvin.

Omicron2 Centauri Radius has been calculated as being 77.19 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 53,711,396.17.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 121.22. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Omicron2 Centauri Apparent and Absolute Magnitudes

Omicron2 Centauri has an apparent magnitude of 5.12 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 -4.97 If you used the 2007 Parallax value, you would get an absolute magnitude of -5.95. 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 Omicron2 Centauri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.96 which gave the calculated distance to Omicron2 Centauri as 3397.53 light years away from Earth or 1041.67 parsecs. It would take a spaceship travelling at the speed of light, 3397.53 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 0.61 which put Omicron2 Centauri at a distance of 5346.94 light years or 1639.34 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 Omicron2 Centauri

The star is a pulsating Alpha Cygnus 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. Omicron2 Centauri brightness ranges from a magnitude of 5.281 to a magnitude of 5.233 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 days (variability).

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.

Omicron2 Centauri Facts

Alternative Names

Short Nameomi02 Cen
Bayer DesignationOmicron2 Centauri
Hipparcos Library I.D.56250
Gould I.D.38
Henry Draper Designation100262

Visual Facts

Star Typesupergiant star
Absolute Magnitude-4.97 / -5.95
Visual / Apparent Magnitude5.12
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)11h 31m 48.81
Declination (Dec.)-59d30`56.3
Galactic Latitude1.81 degrees
Galactic Longitude292.98 degrees
1997 Distance from Earth0.96 Parallax (milliarcseconds)
 3397.53 Light Years
 1041.67 Parsecs
2007 Revised Distance from Earth0.61 Parallax (milliarcseconds)
 5346.94 Light Years
 1639.34 Parsecs
Proper Motion Dec.1.12 ± 0.20 milliarcseconds/year
Proper Motion RA.-6.89 ± 0.28 milliarcseconds/year
B-V Index0.43
Radial Velocity-16.80 ± 2.80 km/s
Spectral TypeA3Ia
Colour(A) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeAlpha Cygnus
Mean Variability Period in Days0.044
Variable Magnitude Range (Brighter - Dimmer)5.233 - 5.281

Estimated Facts

Calculated Effective Temperature6,305 Kelvin

Sources and Links

SIMBAD SourceLink

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