Universe Guide


VW Cephei - HD197433 - HIP101750

VW Cephei is a orange to red eclipsing main sequence dwarf star that can be located in the constellation of Cepheus. 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. VW Cephei has alternative name(s), VW_Cep.

Location of VW 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 VW Cephei, the location is 20h 37m 20.82 and +75d35`56.7 .

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 ± 000.49 towards the north and 308.71 ± 000.58 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) 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 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 has been calculated as 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.

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.

Variable Type of VW Cephei

The star is a eclipsing W Ursae Majoris/Contact systems of the W UMa type, with ellipsoidal components of F0-K spectral type 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 8.000 to a magnitude of 7.000 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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

VW Cephei Facts

Alternative Names

Traditional NameVW Cephei
Short NameVW Cep
Hipparcos Library I.D.101750
Bonner DurchmusterungBD+75 752
Henry Draper Designation197433

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude5.25 / 5.26
Apparent Magnitude7.46
Right Ascension (R.A.)20h 37m 20.82
Declination (Dec.)+75d35`56.7
1997 Distance from Earth36.16 Parallax (milliarcseconds)
 90.20 Light Years
 27.65 Parsecs
2007 Revised Distance from Earth36.25 Parallax (milliarcseconds)
 89.98 Light Years
 27.59 Parsecs
Proper Motion Dec.540.86 ± 0.49 milliarcseconds/year
Proper Motion RA.308.71 ± 0.58 milliarcseconds/year
B-V Index0.85
Spectral TypeK0Vvar
Colour(K) Orange to Red

Variable Star Details

Variable Star ClassEclipsing
Variable Star TypeW Ursae Majoris/Contact systems of the W UMa type, with ellipsoidal components of F0-K spectral type
Variable Magnitude Range (Brighter - Dimmer)7.000 - 8.000

Estimated Facts

Radius (x the Sun)1.04
Calculated Effective Temperature5,164 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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

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