Universe Guide


Alpha Octantis - HD199532 - HIP104043

Alpha Octantis is a blue to white eclipsing binary system giant star that can be located in the constellation of Octans. Alpha Octantis is the Bayer Classification for the star. HIP104043 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD199532. Alpha Octantis has alternative name(s), alf_Oct.

Location of Alpha Octantis

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 Alpha Octantis, the location is 21h 04m 43.03 and -77d01`22.3 .

Proper Motion of Alpha Octantis

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 -369.24 ± 000.17 towards the north and 012.74 ± 000.23 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Alpha Octantis

Alpha Octantis has a spectral type of F4III. This means the star is a blue to white giant star. The star has a B-V Colour Index of 0.49 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,327 Kelvin.

Alpha Octantis has been calculated as 3.32 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,306,609.09.km.

Alpha Octantis Apparent and Absolute Magnitudes

Alpha Octantis has an apparent magnitude of 5.13 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 1.85 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.94. 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 Alpha Octantis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 22.07 which gave the calculated distance to Alpha Octantis as 147.79 light years away from Earth or 45.31 parsecs. It would take a spaceship travelling at the speed of light, 147.79 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 22.97 which put Alpha Octantis at a distance of 142.00 light years or 43.54 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 Alpha Octantis

The star is a eclipsing binary system Beta Lyrae (Sheliak) 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. Alpha Octantis brightness ranges from a magnitude of 5.000 to a magnitude of 5.000 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 3.0 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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Alpha Octantis Facts

Alternative Names

Short Namealf Oct
Bayer DesignationAlpha Octantis
Hipparcos Library I.D.104043
Henry Draper Designation199532

Visual Facts

Star Typegiant star
Absolute Magnitude1.85 / 1.94
Apparent Magnitude5.13
Right Ascension (R.A.)21h 04m 43.03
Declination (Dec.)-77d01`22.3
1997 Distance from Earth22.07 Parallax (milliarcseconds)
 147.79 Light Years
 45.31 Parsecs
2007 Revised Distance from Earth22.97 Parallax (milliarcseconds)
 142.00 Light Years
 43.54 Parsecs
Proper Motion Dec.-369.24 ± 0.17 milliarcseconds/year
Proper Motion RA.12.74 ± 0.23 milliarcseconds/year
B-V Index0.49
Spectral TypeF4III
Colour(F) blue to white

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeBeta Lyrae (Sheliak)
Mean Variability Period in Days3.000

Estimated Facts

Radius (x the Sun)3.32
Calculated Effective Temperature6,327 Kelvin

Sources and Links

SIMBAD SourceLink

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