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EK Cephei, HD206821, HIP107083

EK Cephei is a blue eclipsing main sequence dwarf star that can be located in the constellation of Cepheus. The star can not be seen by the naked eye, you need a telescope to see it.

HIP107083 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD206821.

EK Cephei has alternative name(s), EK Cep.

Location of EK Cephei

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 EK Cephei, the location is 21h 41m 21.47 and +69d41`34.1 .

Proper Motion of EK Cephei

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 4.58 ± 0.35 miliarcseconds/year towards the north and 22.33 ± 0.41 miliarcseconds/year east if we saw them in the horizon.

EK Cephei 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 20.0000000 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 EK Cephei

EK Cephei has a spectral type of A1V. This means the star is a blue main sequence dwarf star. The star is 7450.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24299.1691280000000000s. The star has a B-V Colour Index of 0.06 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 8,815 Kelvin.

EK Cephei Radius has been calculated as being 1.63 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,134,812.35.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.72. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

EK Cephei Apparent and Absolute Magnitudes

EK Cephei has an apparent magnitude of 7.88 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 1.95 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.83. 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 EK Cephei

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 6.53 which gave the calculated distance to EK Cephei as 499.48 light years away from Earth or 153.14 parsecs. It would take a spaceship travelling at the speed of light, 499.48 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 6.18 which put EK Cephei at a distance of 527.77 light years or 161.81 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.

The star's Galacto-Centric Distance is 7,450.00 Parsecs or 24,299.17 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 EK Cephei

The star is a eclipsing Beta Persei (Algol)/Detached Main Sequence (subtype) 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. EK Cephei brightness ranges from a magnitude of 9.060 to a magnitude of 7.880 over its variable period. The smaller the magnitude, the brighter the star.

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.

EK Cephei Facts

Alternative Names

Traditional/Proper NameEK Cephei
Short NameEK Cep
Hipparcos Library I.D.107083
Bonner DurchmusterungBD+69 1191
Henry Draper Designation206821

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude1.95 / 1.83
Visual / Apparent Magnitude7.88
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)21h 41m 21.47
Declination (Dec.)+69d41`34.1
Galactic Latitude12.65 degrees
Galactic Longitude107.72 degrees
1997 Distance from Earth6.53 Parallax (milliarcseconds)
 499.48 Light Years
 153.14 Parsecs
2007 Revised Distance from Earth6.18 Parallax (milliarcseconds)
 527.77 Light Years
 161.81 Parsecs
Galacto-Centric Distance24,299.17 Light Years / 7,450.00 Parsecs
Proper Motion Dec.4.58 ± 0.35 milliarcseconds/year
Proper Motion RA.22.33 ± 0.41 milliarcseconds/year
B-V Index0.06
Radial Velocity-10.90 ± 0.74 km/s
Spectral TypeA1V
Colour(A) blue

Variable Star Details

Variable Star ClassEclipsing
Variable Star TypeBeta Persei (Algol)/Detached Main Sequence (subtype)
Variable Magnitude Range (Brighter - Dimmer)7.880 - 9.060

Estimated Facts

Luminosity (x the Sun)20.0000000
Calculated Effective Temperature8,815 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars


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