V438 Cephei is a red pulsating star that can be located in the constellation of Cepheus. HIP108133 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD209111. V438 Cephei has alternative name(s), V438_Cep.
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 V438 Cephei, the location is 21h 54m 26.54 and +80d18`30.9 .
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 -014.30 ± 000.26 towards the north and 002.66 ± 000.32 east if we saw them in the horizon.
V438 Cephei has a spectral type of M3. This means the star is a red star. The star has a B-V Colour Index of 1.45 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,115 Kelvin.
V438 Cephei has been calculated as 24.11 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 16,774,668.39.km.
V438 Cephei has an apparent magnitude of 6.43 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 -0.59 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.35. 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.
Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.95 which gave the calculated distance to V438 Cephei as 825.73 light years away from Earth or 253.16 parsecs. It would take a spaceship travelling at the speed of light, 825.73 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 4.41 which put V438 Cephei at a distance of 739.60 light years or 226.76 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 is a pulsating Semiregular s, which are giants or supergiants of intermediate and late spectral 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. V438 Cephei brightness ranges from a magnitude of 6.000 to a magnitude of 6.000 over its variable period. The smaller the magnitude, the brighter the star.
|Traditional Name||V438 Cephei|
|Short Name||V438 Cep|
|Hipparcos Library I.D.||108133|
|Bonner Durchmusterung||BD+79 721|
|Henry Draper Designation||209111|
|Absolute Magnitude||-0.59 / -0.35|
|Right Ascension (R.A.)||21h 54m 26.54|
|1997 Distance from Earth||3.95 Parallax (milliarcseconds)|
|825.73 Light Years|
|2007 Revised Distance from Earth||4.41 Parallax (milliarcseconds)|
|739.60 Light Years|
|Proper Motion Dec.||-14.30 ± 0.26 milliarcseconds/year|
|Proper Motion RA.||2.66 ± 0.32 milliarcseconds/year|
|Variable Star Class||Pulsating|
|Variable Star Type||Semiregular s, which are giants or supergiants of intermediate and late spectral|
|Radius (x the Sun)||24.11|
|Calculated Effective Temperature||4,115 Kelvin|