Polaris Australis (Sigma Octantis) is a blue to white pulsating giant star that can be located in the constellation of Octans. Sigma Octantis is the Bayer Classification for the star. HIP104382 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD177482. Polaris Australis has alternative name(s), sig_Oct.
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 Polaris Australis, the location is 21h 08m 46.01 and -88d57`23.4 .
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 004.98 ± 000.26 towards the north and 025.75 ± 000.31 east if we saw them in the horizon.
Polaris Australis has a spectral type of F0III. This means the star is a blue to white giant star. The star has a B-V Colour Index of 0.28 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,322 Kelvin.
Polaris Australis has been calculated as 3.91 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,717,189.56.km.
Polaris Australis has an apparent magnitude of 5.45 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 0.86 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.77. 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.
Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 12.07 which gave the calculated distance to Polaris Australis as 270.23 light years away from Earth or 82.85 parsecs. In 2007, Hipparcos data was revised with a new parallax of 11.61 which put Polaris Australis at a distance of 280.93 light years or 86.13 parsecs.
It would take a spaceship travelling at the speed of light, 270.23 years using the 1997 distance to get there. We don't have the technology or spaceship that can carry people over that distance yet.
The star is a pulsating Delta Scuti 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. Polaris Australis brightness ranges from a magnitude of 6.000 to a magnitude of 5.000 over its variable period. The smaller the magnitude, the brighter the star.
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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.
|Traditional Name||Polaris Australis|
|Short Name||sig Oct|
|Bayer Designation||Sigma Octantis|
|Hipparcos Library I.D.||104382|
|Henry Draper Designation||177482|
|Star Type||giant star|
|Absolute Magnitude||0.86 / 0.77|
|Right Ascension (R.A.)||21h 08m 46.01|
|1997 Distance from Earth||12.07 Parallax (milliarcseconds)|
|270.23 Light Years|
|2007 Distance from Earth||11.61 Parallax (milliarcseconds)|
|280.93 Light Years|
|Proper Motion Dec.||4.98 ± 0.26 milliarcseconds/year|
|Proper Motion RA.||25.75 ± 0.31 milliarcseconds/year|
|Colour||(F) blue to white|
|Variable Star Class||Pulsating|
|Variable Star Type||Delta Scuti|
|Variable Magnitude Range (Brighter - Dimmer)||5.000 - 6.000|
|Radius (x the Sun)||3.91|
|Calculated Effective Temperature||7,322 Kelvin|
The map was generated using Night Vision, an awesome free application by Brian Simpson.