RW Cephei is a white to yellow pulsating supergiant 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.
RW Cephei's Alternative Names
HIP110504 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD212466.
RW Cephei has alternative name(s) :- Herschel`s Garnet Star, RW 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+55 2737.
More details on star alternative names can be found at Star Names .
Location of RW 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 RW Cephei, the location is 22h 23m 07.02 and +55° 57` 47.6 .
Radial Velocity and Proper Motion of RW 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 -2.66 ± 0.29 miliarcseconds/year towards the north and -2.74 ± 0.36 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 -56.00 km/s with an error of about 5.70 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.
Physical Properties (Colour, Temperature, Radius) of RW Cephei
RW Cephei has a spectral type of G8Iavar. This means the star is a white to yellow supergiant star. The star has a B-V Colour Index of 2.21 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 590 Kelvin.
RW Cephei has been calculated as 1,535.00 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,068,053,000.00.km. If you need the diameter of the star, you just need to multiple the radius by 2.
RW Cephei Apparent and Absolute Magnitudes
RW Cephei has an apparent magnitude of 6.44 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 -3.18 If you used the 2007 Parallax value, you would get an absolute magnitude of -4.02. 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 RW Cephei
Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.19 which gave the calculated distance to RW Cephei as 2740.87 light years away from Earth or 840.34 parsecs. It would take a spaceship travelling at the speed of light, 2740.87 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 0.81 which put RW Cephei at a distance of 4026.71 light years or 1234.57 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 RW Cephei
The star is a pulsating Slow Irregular 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. RW Cephei brightness ranges from a magnitude of 6.620 to a magnitude of 6.456 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 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.
Alternative NamesRw Cep, Herschel`s Garnet Star, HD 212466, HIP 110504, BD+55 2737, RW Cep
Spectral TypeG8Iavar
Multiple Star SystemNo / Unknown
Star Typevery luminous Supergiant Star
Colourwhite to yellow
GalaxyMilky Way
ConstellationCepheus
Absolute Magnitude-3.18 / -4.02
Visual / Apparent Magnitude6.44
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)22h 23m 07.02
Declination (Dec.)+55° 57` 47.6
Galactic Latitude-1.12 degrees
Galactic Longitude103.20 degrees
1997 Distance from Earth1.19 Parallax (milliarcseconds)
2740.87 Light Years
840.34 Parsecs
2007 Distance from Earth0.81 Parallax (milliarcseconds)
4026.71 Light Years
1234.57 Parsecs
Proper Motion Dec.-2.66 ± 0.29 milliarcseconds/year
Proper Motion RA.-2.74 ± 0.36 milliarcseconds/year
B-V Index2.21
Radial Velocity-56.00 ± 5.70 km/s
Companions (Multi-Star and Exoplanets) Facts
Exoplanet CountNone/Unaware
Variable Star Details
Variable Star ClassPulsating
Variable Star TypeSlow Irregular
Mean Variability Period in Days0.170
Variable Magnitude Range (Brighter - Dimmer)6.456 - 6.620
Estimated Facts
Radius (x the Sun)1,535.00
Calculated Effective Temperature590 Kelvin
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