Universe Guide


X Oct, HD91620, HIP51084

X Oct is a red pulsating star that can be located in the constellation of Octans. The star can not be seen by the naked eye, you need a telescope to see it.

HIP51084 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD91620.

X Oct has alternative name(s), X Oct.

Location of X 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 X Oct, the location is 10h 26m 14.33 and -84d20`54.1 .

Proper Motion of X Oct

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 17.21 ± 0.59 miliarcseconds/year towards the north and -15.02 ± 0.77 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of X Oct

X Oct has a spectral type of M5/M6e. This means the star is a red star. The star has a B-V Colour Index of 1.53 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,949 Kelvin.

X Oct Radius has been calculated as being 20.51 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 14,269,677.30.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 14.12. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

X Oct Apparent and Absolute Magnitudes

X Oct has an apparent magnitude of 8.18 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 -0.06 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.75. 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 X Oct

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.25 which gave the calculated distance to X Oct as 1449.61 light years away from Earth or 444.44 parsecs. It would take a spaceship travelling at the speed of light, 1449.61 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 3.27 which put X Oct at a distance of 997.44 light years or 305.81 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 X Oct

The star is a pulsating Semi-Regular Star which are giants or supergiants of intermediate and late 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. X Oct brightness ranges from a magnitude of 9.595 to a magnitude of 7.265 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 197.7 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.

X Oct Facts

Alternative Names

Traditional/Proper NameX Oct
Short NameX Oct
Hipparcos Library I.D.51084
Henry Draper Designation91620

Visual Facts

Star Type star
Absolute Magnitude-0.06 / 0.75
Visual / Apparent Magnitude8.18
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)10h 26m 14.33
Declination (Dec.)-84d20`54.1
Galactic Latitude-22.53 degrees
Galactic Longitude299.31 degrees
1997 Distance from Earth2.25 Parallax (milliarcseconds)
 1449.61 Light Years
 444.44 Parsecs
2007 Revised Distance from Earth3.27 Parallax (milliarcseconds)
 997.44 Light Years
 305.81 Parsecs
Proper Motion Dec.17.21 ± 0.59 milliarcseconds/year
Proper Motion RA.-15.02 ± 0.77 milliarcseconds/year
B-V Index1.53
Radial Velocity-1.00 ± 2.50 km/s
Spectral TypeM5/M6e
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemi-Regular Star which are giants or supergiants of intermediate and late spectral
Mean Variability Period in Days197.700
Variable Magnitude Range (Brighter - Dimmer)7.265 - 9.595

Estimated Facts

Calculated Effective Temperature3,949 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Add a Comment

Email: (Optional)