Universe Guide


Errai (Gamma Cephei) - HD222404 - HIP116727 - HR8974

Errai (Gamma Cephei) is a orange to red subgiant star that can be located in the constellation of Cepheus. It is calculated at being 7.000 Billion Years old. This information comes from ExoPlanet. Gamma Cephei is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR8974. HIP116727 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD222404. Errai has alternative name(s), 35 Cephei , 35 Cep.

Location of Errai

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 Errai, the location is 23h 39m 20.98 and +77d37`55.1 .

Proper Motion of Errai

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 126.59 ± 000.33 towards the north and -047.96 ± 000.40 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Metallicity, Age, Mass, Radius) of Errai

Errai has a spectral type of K1IV. This means the star is a orange to red subgiant star. The star has a B-V Colour Index of 1.03 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,792 Kelvin.

Errai has been calculated as 4.26 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,967,082.14.km. The star's solar mass is 1.00 times that of the Sun's. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

The star's metallicity is 0.180000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

The star is believed to be about 7.00 Billion years old. To put in context, the Sun is believed to be about five billion years old and the Universe is about 13.8 billion years old.

Errai Apparent and Absolute Magnitudes

Errai has an apparent magnitude of 3.21 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 2.51 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.46. 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 Errai

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 72.50 which gave the calculated distance to Errai as 44.99 light years away from Earth or 13.79 parsecs. It would take a spaceship travelling at the speed of light, 44.99 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 70.91 which put Errai at a distance of 46.00 light years or 14.10 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.

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.

Errai Facts

Alternative Names

Traditional NameErrai
Short Name35 Cep
Bayer DesignationGamma Cephei
Alternative Name(s)35 Cephei
Hipparcos Library I.D.116727
Yale Bright Star Catalogue (HR) Id8974
Bonner DurchmusterungBD+76 928
Henry Draper Designation222404

Visual Facts

Star Typesubgiant star
Age7.000 Billions of Years
Absolute Magnitude2.51 / 2.46
Apparent Magnitude3.21
Right Ascension (R.A.)23h 39m 20.98
Declination (Dec.)+77d37`55.1
1997 Distance from Earth72.50 Parallax (milliarcseconds)
 44.99 Light Years
 13.79 Parsecs
2007 Revised Distance from Earth70.91 Parallax (milliarcseconds)
 46.00 Light Years
 14.10 Parsecs
Proper Motion Dec.126.59 ± 0.33 milliarcseconds/year
Proper Motion RA.-47.96 ± 0.40 milliarcseconds/year
B-V Index1.03
Spectral TypeK1IV
Colour(K) Orange to Red

Estimated Facts

Radius (x the Sun)4.26
Calculated Effective Temperature4,792 Kelvin
Mass Compared to the Sun1.00

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Errai in Cepheus

Errai (Gamma Cephei) Location in Cepheus

The map was generated using Night Vision, an awesome free application by Brian Simpson.

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