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VW Cephei, HD197433, HIP101750

Primary Facts on VW Cephei

  • VW Cephei's star type is eclipsing main sequence dwarf star that can be located in the constellation of Cepheus. The description is based on the spectral class.
  • VW Cephei is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (K0Vvar) of the star, the star's colour is orange to red .
  • The star can not be seen by the naked eye, you need a telescope to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 89.98 light years away from us.

VW Cephei's Alternative Names

HIP101750 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD197433. The Gliese ID of the star is GJ 1255A. The star was added to the Gliese catalogue in 1970 by Richard van der Riet Woolley hence the GJ prefix rather than GL prefix.Star Names.

VW Cephei has alternative name(s) :- , VW 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+75 752.

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

Location of VW 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 VW Cephei, the location is 20h 37m 20.82 and +75° 35` 56.7 .

Radial Velocity and Proper Motion of VW 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 540.86 ± 0.49 miliarcseconds/year towards the north and 308.71 ± 0.58 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 the Sun is -7.90 km/s with an error of about 1.00 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.

VW 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 0.84 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 VW Cephei

VW Cephei has a spectral type of K0Vvar. This means the star is a orange to red main sequence dwarf star. The star is 7,409.00 Parsecs from the Galactic Centre or in terms of Light Years is 24,165.44 s. The star has a B-V Colour Index of 0.85 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,164 Kelvin.

VW Cephei Radius has been calculated as being 1.04 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 723,375.54.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 1.03. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

VW Cephei Apparent and Absolute Magnitudes

VW Cephei has an apparent magnitude of 7.46 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 5.25 If you used the 2007 Parallax value, you would get an absolute magnitude of 5.26. 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 VW Cephei

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 36.16 which gave the calculated distance to VW Cephei as 90.20 light years away from Earth or 27.65 parsecs. It would take a spaceship travelling at the speed of light, 90.20 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 36.25 which put VW Cephei at a distance of 89.98 light years or 27.59 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 5,690,806.35 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*.

Variable Type of VW Cephei

The star is a eclipsing W Ursae Majoris/Cont 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. VW Cephei brightness ranges from a magnitude of 7.825 to a magnitude of 7.477 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.3 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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Additional VW Cephei Facts and Figures

Visual Facts


Primary / Proper / Traditional NameVW Cephei
Alternative NamesHD 197433, HIP 101750, BD+75 752, Gliese 1255A, VW Cep
Spectral TypeK0Vvar
Constellation's Main StarNo
Multiple Star SystemYes
Star Type main sequence Dwarf Star
Colour orange to red
GalaxyMilky Way
ConstellationCepheus
Absolute Magnitude 5.25 / 5.26
Visual / Apparent Magnitude7.46
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)20h 37m 20.82
Declination (Dec.)+75° 35` 56.7
Galactic Latitude20.06 degrees
Galactic Longitude109.22 degrees
1997 Distance from Earth36.16 Parallax (milliarcseconds)
 90.20 Light Years
 27.65 Parsecs
2007 Distance from Earth36.25 Parallax (milliarcseconds)
 89.98 Light Years
 27.59 Parsecs
 5,690,806.35 Astronomical Units
Galacto-Centric Distance24,165.44 Light Years / 7,409.00 Parsecs
Proper Motion Dec.540.86 ± 0.49 milliarcseconds/year
Proper Motion RA.308.71 ± 0.58 milliarcseconds/year
B-V Index0.85
Radial Velocity-7.90 ± 1.00 km/s
Eccentricity0.33
Semi-Major Axis6392.00
Stellar Luminosity (Lsun)0.84

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing
Variable Star TypeW Ursae Majoris/Cont
Mean Variability Period in Days0.278
Variable Magnitude Range (Brighter - Dimmer)7.477 - 7.825

Estimated Facts


Calculated Effective Temperature5,164 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
197433+75 752.0A7.60000338.00000557.00000G5Yellow
B10.500001974

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