Universe Guide

Kurhah (Xi Cephei, 17 Cephei A) Star Facts

Kurhah Facts

Kurhah's Alternative Names

Xi Cephei (Ksi Cep) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in the early nineteenth century. The brightest star in the constellation is normally given the Alpha designation although there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR8417. HIP108917 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD209790.

Kurhah has alternative name(s) :- Al Kurhah, Alkurhah, KSI Cephei, KSI Cep.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 17 Cephei A with it shortened to 17 Cep A.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+63 1802.

More details on objects' alternative names can be found at Star Names .

Location of Kurhah

The location of the multiple star system in the night sky 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 object is compared to the celestial equator and is expressed in degrees. For Kurhah, the location is 22h 03m 47.16 and +64° 37` 39.9 .

Radial Velocity and Proper Motion of Kurhah

Proper Motion

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 91.06 ± 0.84 milliarcseconds/year towards the north and 215.46 ± 1.06 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -10.74 km/s with an error of about 0.34 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Kurhah 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 16.01 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of Kurhah

Kurhah Colour and Temperature

Kurhah has a spectral type of Am. This means the star is a blue - white multiple star system. The star has a B-V Colour Index of 0.37 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,501 Kelvin.

Kurhah Radius

Radius has been calculated as being 3.23 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,246,000.89.km. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 3.07. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Kurhah Apparent and Absolute Magnitudes

Kurhah has an apparent magnitude of 4.26 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 1.79 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.90. 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 Kurhah

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 32.07 which gave the calculated distance to Kurhah as 101.70 light years away from Earth or 31.18 parsecs. It would take a spaceship travelling at the speed of light, 101.70 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 33.79 which put Kurhah at a distance of 96.53 light years or 29.59 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.

Using the 2007 distance, the star is roughly 6,103,333.09 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun.

The star's Galacto-Centric Distance is 7,409.00 Parsecs or 24,165.44 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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.

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Additional Kurhah Facts and Figures

Visual Facts

Primary / Proper / Traditional NameKurhah
Alternative NamesXi Cephei, Ksi Cep, Al Kurhah, Alkurhah, KSI Cephei, KSI Cep, HD 209790, HIP 108917, HR 8417, 17 Cephei A, 17 Cep A, BD+63 1802
Spectral TypeAm
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeMultiple Star System
GalaxyMilky Way
Absolute Magnitude 1.79 / 1.90
Visual / Apparent Magnitude4.26
Naked Eye Visible Yes - Magnitudes
Right Ascension (R.A.)22h 03m 47.16
Declination (Dec.)+64° 37` 39.9
Galactic Latitude7.37 degrees
Galactic Longitude106.16 degrees
1997 Distance from Earth32.07 Parallax (milliarcseconds)
 101.70 Light Years
 31.18 Parsecs
2007 Distance from Earth33.79 Parallax (milliarcseconds)
 96.53 Light Years
 29.59 Parsecs
 6,103,333.09 Astronomical Units
Galacto-Centric Distance24,165.44 Light Years / 7,409.00 Parsecs
Proper Motion Dec.91.06 ± 0.84 milliarcseconds/year
Proper Motion RA.215.46 ± 1.06 milliarcseconds/year
B-V Index0.37
Radial Velocity-10.74 ± 0.34 km/s
Semi-Major Axis7170.00
Stellar Luminosity (Lsun)16.01
Associated / Clustered StarsKSI Cephei B

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Estimated Calculated Facts

Radius (x the Sun)3.07
Effective Temperature6,501 Kelvin

Sources and Links

SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.

Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
209790+63 1802.0A4.60000209.0000089.00000A3White

Location of Kurhah in Cepheus

Kurhah Location in Cepheus

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

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