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Rho1 Cephei, 28 Cephei, HD213403, HIP110787, HR8578

Rho1 Cephei is a blue multiple star system 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.

Rho1 Cephei's Alternative Names

(Rho1 Cephei) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR8578. HIP110787 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD213403.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 28 Cephei with it shortened to 28 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+78 796.

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

Location of Rho1 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 Rho1 Cephei, the location is 22h 26m 42.45 and +78° 47` 09.4 .

Proper Motion of Rho1 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 -36.95 ± 0.20 miliarcseconds/year towards the north and -13.33 ± 0.23 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 -6.00000 km/s with an error of about 3.80 km/s .

Rho1 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 15.47 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 Rho1 Cephei

Rho1 Cephei has a spectral type of A2m. This means the star is a blue multiple star system. The star is 7,427.00 Parsecs from the Galactic Centre or terms of Light Years is 24,224.15 s. The star has a B-V Colour Index of 0.17 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,653 Kelvin.

Rho1 Cephei Radius has been calculated as being 2.27 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,576,544.53.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 2.29. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Rho1 Cephei Apparent and Absolute Magnitudes

Rho1 Cephei has an apparent magnitude of 5.83 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 1.85 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.83. 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 Rho1 Cephei

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 15.98 which gave the calculated distance to Rho1 Cephei as 204.11 light years away from Earth or 62.58 parsecs. It would take a spaceship travelling at the speed of light, 204.11 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 15.83 which put Rho1 Cephei at a distance of 206.04 light years or 63.17 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 7,427.00 Parsecs or 24,224.15 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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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Rho1 Cephei Facts

Visual Facts


Primary / Proper / Traditional NameRho1 Cephei
Alternative NamesHD 213403, HIP 110787, HR 8578, 28 Cephei, 28 Cep, BD+78 796
Spectral TypeA2m
Multiple Star SystemYes
Star TypeMultiple Star System
Colour blue
GalaxyMilky Way
ConstellationCepheus
Absolute Magnitude1.85 / 1.83
Visual / Apparent Magnitude5.83
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)22h 26m 42.45
Declination (Dec.)+78° 47` 09.4
Galactic Latitude17.91 degrees
Galactic Longitude116.00 degrees
1997 Distance from Earth15.98 Parallax (milliarcseconds)
 204.11 Light Years
 62.58 Parsecs
2007 Distance from Earth15.83 Parallax (milliarcseconds)
 206.04 Light Years
 63.17 Parsecs
Galacto-Centric Distance24,224.15 Light Years / 7,427.00 Parsecs
Proper Motion Dec.-36.95 ± 0.20 milliarcseconds/year
Proper Motion RA.-13.33 ± 0.23 milliarcseconds/year
B-V Index0.17
Radial Velocity-6.00 ± 3.80 km/s
Eccentricity0.20
Semi-Major Axis8783.00
Stellar Luminosity (Lsun)15.47
Associated / Clustered StarsAl Kalb al Rai

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature7,653 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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