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V421 Cephei, HD203025, HIP105091

V421 Cephei is a blue eclipsing giant star that can be located in the constellation of Cepheus. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

V421 Cephei's Alternative Names

HIP105091 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD203025.

V421 Cephei has alternative name(s) :- , V421 Cep.

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+57 2309.

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

Location of V421 Cephei

The location of the star 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 star is compared to the celestial equator and is expressed in degrees. For V421 Cephei, the location is 21h 17m 18.79 and +58° 36` 41.4 .

Proper Motion of V421 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 -3.20 ± 0.25 miliarcseconds/year towards the north and -3.34 ± 0.29 miliarcseconds/year east if we saw them in the horizon. The Radial Velocity, that is the speed at which the star is moving away/towards us is -6.10000 km/s with an error of about 7.40 km/s .

Physical Properties (Colour, Temperature) of V421 Cephei

V421 Cephei has a spectral type of B2III. This means the star is a blue giant star. The star has a B-V Colour Index of 0.19 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,827 Kelvin.

V421 Cephei Radius has been calculated as being 20.50 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 14,263,526.38.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 22.17. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

V421 Cephei Apparent and Absolute Magnitudes

V421 Cephei has an apparent magnitude of 6.42 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 -3.03 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.20. 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 V421 Cephei

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.29 which gave the calculated distance to V421 Cephei as 2528.40 light years away from Earth or 775.19 parsecs. It would take a spaceship travelling at the speed of light, 2528.40 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 1.19 which put V421 Cephei at a distance of 2740.87 light years or 840.34 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 V421 Cephei

The star is a eclipsing Beta Lyrae (Sheliak) 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. This is a some uncertainty as to the type but the type mentioned is the current variable star classification for this star. V421 Cephei brightness ranges from a magnitude of 6.509 to a magnitude of 6.449 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.

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V421 Cephei Facts

Visual Facts


Primary / Proper / Traditional NameV421 Cephei
Alternative NamesHD 203025, HIP 105091, BD+57 2309, V421 Cep
Spectral TypeB2III
Multiple Star SystemYes
Star TypeGiant Star
Colour blue
GalaxyMilky Way
ConstellationCepheus
Absolute Magnitude-3.03 / -3.20
Visual / Apparent Magnitude6.42
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)21h 17m 18.79
Declination (Dec.)+58° 36` 41.4
Galactic Latitude6.53 degrees
Galactic Longitude98.00 degrees
1997 Distance from Earth1.29 Parallax (milliarcseconds)
 2528.40 Light Years
 775.19 Parsecs
2007 Distance from Earth1.19 Parallax (milliarcseconds)
 2740.87 Light Years
 840.34 Parsecs
Proper Motion Dec.-3.20 ± 0.25 milliarcseconds/year
Proper Motion RA.-3.34 ± 0.29 milliarcseconds/year
B-V Index0.19
Radial Velocity-6.10 ± 7.40 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing
Variable Star TypeBeta Lyrae (Sheliak) probably
Mean Variability Period in Days0.047
Variable Magnitude Range (Brighter - Dimmer)6.449 - 6.509

Estimated Facts


Calculated Effective Temperature7,827 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
203025+57 2309.0A6.40000-8.00000-2.00000B3Blue/White
B12.000001889
C12.600001912

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