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V438 Cephei, HD209111, HIP108133

V438 Cephei is a red pulsating variable 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.

V438 Cephei's Alternative Names

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.

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+79 721.

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

Location of V438 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 V438 Cephei, the location is 21h 54m 26.54 and +80° 18` 30.9 .

Proper Motion of V438 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 -14.30 ± 0.26 miliarcseconds/year towards the north and 2.66 ± 0.32 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 -63.59000 km/s with an error of about 0.16 km/s .

V438 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 298.71 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 V438 Cephei

V438 Cephei has a spectral type of M3. This means the star is a red variable star. The star is 7,495.00 Parsecs from the Galactic Centre or terms of Light Years is 24,445.94 s. 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 Radius has been calculated as being 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. 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 21.59. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

V438 Cephei Apparent and Absolute Magnitudes

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.

Distance to V438 Cephei

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's Galacto-Centric Distance is 7,495.00 Parsecs or 24,445.94 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 V438 Cephei

The star is a pulsating Semi-Regular Star 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 6.488 to a magnitude of 6.318 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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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V438 Cephei Facts

Visual Facts

Primary / Proper / Traditional NameV438 Cephei
Alternative NamesHD 209111, HIP 108133, BD+79 721, V438 Cep
Spectral TypeM3
Multiple Star SystemNo / Unknown
Star TypeVariable Star
Colour red
GalaxyMilky Way
Absolute Magnitude-0.59 / -0.35
Visual / Apparent Magnitude6.43
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)21h 54m 26.54
Declination (Dec.)+80° 18` 30.9
Galactic Latitude20.01 degrees
Galactic Longitude115.75 degrees
1997 Distance from Earth3.95 Parallax (milliarcseconds)
 825.73 Light Years
 253.16 Parsecs
2007 Distance from Earth4.41 Parallax (milliarcseconds)
 739.60 Light Years
 226.76 Parsecs
Galacto-Centric Distance24,445.94 Light Years / 7,495.00 Parsecs
Proper Motion Dec.-14.30 ± 0.26 milliarcseconds/year
Proper Motion RA.2.66 ± 0.32 milliarcseconds/year
B-V Index1.45
Radial Velocity-63.59 ± 0.16 km/s
Semi-Major Axis5932.00
Stellar Luminosity (Lsun)298.71

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemi-Regular Star which are giants or supergiants of intermediate and late spectral
Mean Variability Period in Days0.124
Variable Magnitude Range (Brighter - Dimmer)6.318 - 6.488

Estimated Facts

Calculated Effective Temperature4,115 Kelvin

Sources and Links

SIMBAD SourceLink

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