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Saiph, Kappa Orionis, 53 Orionis, HD38771, HIP27366, HR2004

Saiph (Kappa Orionis) is a blue pulsating very luminous supergiant star that can be located in the constellation of Orion. Saiph is the 59th brightest star in the night sky and the 6th brightest star in Orion 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.

Kappa Orionis is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR2004. HIP27366 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD38771.

Saiph has alternative name(s), Saif Al Jabbar , NSV 02641. In Arabic, it is known as As-Saif.

Location of Saiph

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 Saiph, the location is 05h 47m 45.39 and -09d40`10.6 .

Proper Motion of Saiph

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 -1.28 ± 0.13 miliarcseconds/year towards the north and 1.46 ± 0.22 miliarcseconds/year east if we saw them in the horizon.

Saiph Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 320000.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of Saiph

Saiph has a spectral type of B0.5Iavar. This means the star is a blue supergiant star. The star is 7556.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24644.9022726400000000s. The star has a B-V Colour Index of -0.16 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 17,659 Kelvin.

Saiph Radius has been calculated as being 8.49 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 5,908,826.92.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 7.64. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Saiph Apparent and Absolute Magnitudes

Saiph has an apparent magnitude of 2.07 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 -4.65 If you used the 2007 Parallax value, you would get an absolute magnitude of -4.42. 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 Saiph

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.52 which gave the calculated distance to Saiph as 721.60 light years away from Earth or 221.24 parsecs. It would take a spaceship travelling at the speed of light, 721.60 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 5.04 which put Saiph at a distance of 647.15 light years or 198.41 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.

The star's Galacto-Centric Distance is 7,556.00 Parsecs or 24,644.90 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Saiph

The star is a pulsating Beta Cephei 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. Saiph brightness ranges from a magnitude of 2.021 to a magnitude of 1.986 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.

Saiph Facts

Alternative Names

Traditional/Proper NameSaiph
Flamsteed Name53 Orionis
Flamsteed Short Name53 Ori
Short NameNSV 02641
Arabic NameAs-Saif
English MeaningThe sword
Bayer DesignationKappa Orionis
Alternative Name(s)Saif Al Jabbar
Hipparcos Library I.D.27366
Yale Bright Star Catalogue (HR) Id2004
Bonner DurchmusterungBD-09 1235
Henry Draper Designation38771

Visual Facts

Star Typesupergiant star
Absolute Magnitude-4.65 / -4.42
Visual / Apparent Magnitude2.07
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)05h 47m 45.39
Declination (Dec.)-09d40`10.6
Galactic Latitude-18.50 degrees
Galactic Longitude214.51 degrees
1997 Distance from Earth4.52 Parallax (milliarcseconds)
 721.60 Light Years
 221.24 Parsecs
2007 Revised Distance from Earth5.04 Parallax (milliarcseconds)
 647.15 Light Years
 198.41 Parsecs
Galacto-Centric Distance24,644.90 Light Years / 7,556.00 Parsecs
Proper Motion Dec.-1.28 ± 0.13 milliarcseconds/year
Proper Motion RA.1.46 ± 0.22 milliarcseconds/year
B-V Index-0.16
Radial Velocity20.90 ± 2.30 km/s
Spectral TypeB0.5Iavar
Brightest in Night Sky59th
Colour(B) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeBeta Cephei
Mean Variability Period in Days0.037
Variable Magnitude Range (Brighter - Dimmer)1.986 - 2.021

Estimated Facts

Luminosity (x the Sun)320,000.0000000
Calculated Effective Temperature17,659 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Saiph in Orion


Saiph (Kappa Orionis) Location in Orion

The map was generated using Night Vision, an awesome free application by Brian Simpson.


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