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S Sextantis, HD91637, HIP51791

S Sextantis is a red pulsating star that can be located in the constellation of Sextans. S Sextantis is the brightest star in Sextans based on the Hipparcos 2007 apparent magnitude. The star can not be seen by the naked eye, you need a telescope to see it.

HIP51791 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD91637.

S Sextantis has alternative name(s), S Sex.

Location of S Sextantis

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 S Sextantis, the location is 10h 34m 56.04 and -00d 20` 33.4 .

Proper Motion of S Sextantis

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 -4.83 ± 1.01 miliarcseconds/year towards the north and -0.49 ± 1.36 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of S Sextantis

S Sextantis has a spectral type of M2e-M5e. This means the star is a red star. The star has a B-V Colour Index of 1.59 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,802 Kelvin.

S Sextantis Radius has been calculated as being 13.64 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 9,491,915.99.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 20.18. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

S Sextantis Apparent and Absolute Magnitudes

S Sextantis has an apparent magnitude of 10.14 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 0.99 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.14. 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 S Sextantis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.48 which gave the calculated distance to S Sextantis as 2203.81 light years away from Earth or 675.68 parsecs. It would take a spaceship travelling at the speed of light, 2203.81 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 1.00 which put S Sextantis at a distance of 3261.63 light years or 1000 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 S Sextantis

The star is a pulsating Omicron Ceti 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. S Sextantis brightness ranges from a magnitude of 11.754 to a magnitude of 9.030 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 252.4 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.

S Sextantis Facts

Alternative Names

Traditional/Proper NameS Sextantis
Short NameS Sex
Hipparcos Library I.D.51791
Bonner DurchmusterungBD+00 2671
Henry Draper Designation91637

Visual Facts

Star Type star
Absolute Magnitude0.99 / 0.14
Visual / Apparent Magnitude10.14
Naked Eye VisibleRequires a 4.5 - 6 Inch Telescope - Magnitudes
Right Ascension (R.A.)10h 34m 56.04
Declination (Dec.)-00d 20` 33.4
Galactic Latitude47.22 degrees
Galactic Longitude247.24 degrees
1997 Distance from Earth1.48 Parallax (milliarcseconds)
 2203.81 Light Years
 675.68 Parsecs
2007 Revised Distance from Earth1.00 Parallax (milliarcseconds)
 3261.63 Light Years
 1000 Parsecs
Proper Motion Dec.-4.83 ± 1.01 milliarcseconds/year
Proper Motion RA.-0.49 ± 1.36 milliarcseconds/year
B-V Index1.59
Radial Velocity-4.00 ± 1.70 km/s
Spectral TypeM2e-M5e
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeOmicron Ceti
Mean Variability Period in Days252.400
Variable Magnitude Range (Brighter - Dimmer)9.030 - 11.754

Estimated Facts

Calculated Effective Temperature3,802 Kelvin

Sources and Links

SIMBAD SourceLink

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