Universe Guide

Errai (Gamma Cephei, 35 Cephei) Star Facts

Errai Facts

  • Errai is a subgiant star that can be located in the constellation of Cepheus. The description is based on the spectral class.
  • Errai is a main star of the constellation outline.
  • Based on the spectral type (K1IV) of the star, the star's colour is orange to red .
  • The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • It is calculated at being 6.600 Billion Years old. This information comes from ExoPlanet.
  • Errai has at least 1 Extrasolar Planets believed to be in orbit around the star.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 46.00 light years away from us. Distance

Errai's Alternative Names

Gamma Cephei (Gam Cep) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

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. The Gliese ID of the star is GL 903. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Star Names

Errai has alternative name(s) :- Al Rai.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 35 Cephei. The Flamsteed name can be shortened to 35 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+76 928.

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

Location of Errai

The location of the subgiant 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 object is compared to the celestial equator and is expressed in degrees. For Errai, the location is 23h 39m 20.98 and +77° 37` 55.1 .

Radial Velocity and Proper Motion of Errai

Proper Motion

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 ± 0.33 milliarcseconds/year towards the north and -47.96 ± 0.40 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -42.82000 km/s with an error of about 0.30 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 of Errai

Errai Colour and Temperature

Based on the star's spectral type of K1IV , Errai's colour and type is orange to red subgiant star. The star's effective temperature is 4,761 Kelvin which is cooler than our own Sun's effective Temperature which is 5,777 Kelvin

Errai 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 12.95 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Errai Radius

Errai estimated radius has been calculated as being 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. 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 4.3636070617724903510600408376. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It has been known to produce widely incorrect figures.

Errai Mass

The Errai's solar mass is 1.40 times that of our star, the Sun. 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.

Errai Metalicity

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.

Errai Estimated Age

The star is believed to be about 6.60 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 72.50000 which gave the calculated distance to Errai as 44.99 light years away from Earth or 13.79 parsecs. If you want that in miles, it is about 264,479,355,539,530.61, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 70.91000 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.

Using the 2007 distance, the star is roughly 2,908,313.50 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun. The star's Galacto-Centric Distance is 7,407.00 Parsecs or 24,158.92 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to Errai

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A38073641,913,539.31
Speed of Sound (Mach 1)767.26940,205,410.27
Concorde (Mach 2)1,534.5420,102,678.94
New Horizons Probe33,000934,798.94
Speed of Light670,616,629.0046.00

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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Additional Errai Facts and Figures

Visual Facts

Primary / Proper / Traditional NameErrai
Alternative NamesGamma Cephei, Gam Cep, Al Rai, HD 222404, HIP 116727, HR 8974, 35 Cephei, 35 Cep, BD+76 928, Gliese 903
Spectral TypeK1IV
Constellation's Main StarYes
Multiple Star SystemNo / Unknown
Star TypeSubgiant Star
ColourOrange to Red
GalaxyMilky Way
Age6.60 Billion Years Old
Absolute Magnitude 2.51 / 2.46
Visual / Apparent Magnitude3.21
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)23h 39m 20.98
Declination (Dec.)+77° 37` 55.1
Galactic Latitude15.31508632 degrees
Galactic Longitude118.99220666 degrees
1997 Distance from Earth72.50000 Parallax (milliarcseconds)
 44.99 Light Years
 13.79 Parsecs
2007 Distance from Earth70.91000 Parallax (milliarcseconds)
 46.00 Light Years
 14.10 Parsecs
 2,908,313.50 Astronomical Units
Galacto-Centric Distance24,158.92 Light Years / 7,407.00 Parsecs
Proper Motion Dec.126.59000 ± 0.33000 milliarcseconds/year
Proper Motion RA.-47.96000 ± 0.40000 milliarcseconds/year
B-V Index1.03
Radial Velocity-42.82000 ± 0.30 km/s
Iron Abundance0.1500 ± 9.99 Fe/H
Semi-Major Axis6088.0000000
Stellar Luminosity (Lsun)12.9500000

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count1

Estimated Calculated Facts

Radius (x the Sun)4.36
Effective Temperature4,792 Kelvin
Mass Compared to the Sun1.40

Sources and Links

SIMBAD SourceLink

Location of Errai in Cepheus

Errai Location in Cepheus

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

List of Extrasolar Planets orbiting Errai

NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastronInclination
gamma Cephei bConfirmed4.4903.3000.04920032.0594.6009.600

Cepheus Main Stars

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