Universe Guide

AR Cephei

AR Cephei Facts

AR Cephei's Alternative Names

HIP112882 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD217158.

AR Cephei has alternative name(s) :- , AR 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+84 516.

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

Location of AR Cephei

The location of the giant 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 AR Cephei, the location is 22h 51m 33.68 and +85° 02` 46.9 .

Radial Velocity and Proper Motion of AR Cephei

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 4.16 ± 0.34 milliarcseconds/year towards the north and 27.04 ± 0.39 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 -14.58 km/s with an error of about 0.48 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.

AR 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 247.76 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 AR Cephei

AR Cephei Colour and Temperature

AR Cephei has a spectral type of M4IIIvar. This means the star is a red giant star. The star has a B-V Colour Index of 1.36 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,224 Kelvin.

AR Cephei Radius

Radius has been calculated as being 20.96 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 14,586,259.58.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 20.49. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

AR Cephei Apparent and Absolute Magnitudes

AR Cephei has an apparent magnitude of 7.32 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 -0.40 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 AR Cephei

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.85 which gave the calculated distance to AR Cephei as 1144 light years away from Earth or 350 parsecs. If you want that in miles, it is 767,185,423,576.

In 2007, Hipparcos data was revised with a new parallax of 2.92 which put AR Cephei at a distance of 1117 light years or 342 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 70,542,072.19 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 7,562.00 Parsecs or 24,664.47 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 AR Cephei

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 A3807361,017,770,074.00
Speed of Sound (Mach 1)767.269976,292,245.00
Concorde (Mach 2)1,534.54488,145,486.00
New Horizons Probe33,00022,699,356.00
Speed of Light670,616,629.001,117.00

Variable Type of AR Cephei

The star is a pulsating Semiregular late- (M 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. AR Cephei brightness ranges from a magnitude of 7.275 to a magnitude of 6.982 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.3 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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Additional AR Cephei Facts and Figures

Visual Facts

Primary / Proper / Traditional NameAR Cephei
Alternative NamesHD 217158, HIP 112882, BD+84 516, AR Cep
Spectral TypeM4IIIvar
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeGiant Star
GalaxyMilky Way
Absolute Magnitude -0.40 / -0.35
Visual / Apparent Magnitude7.32
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)22h 51m 33.68
Declination (Dec.)+85° 02` 46.9
Galactic Latitude22.81 degrees
Galactic Longitude120.25 degrees
1997 Distance from Earth2.85 Parallax (milliarcseconds)
 1144 Light Years
 350 Parsecs
2007 Distance from Earth2.92 Parallax (milliarcseconds)
 1117 Light Years
 342 Parsecs
 70,542,072.19 Astronomical Units
Galacto-Centric Distance24,664.47 Light Years / 7,562.00 Parsecs
Proper Motion Dec.4.16 ± 0.34 milliarcseconds/year
Proper Motion RA.27.04 ± 0.39 milliarcseconds/year
B-V Index1.36
Radial Velocity-14.58 ± 0.48 km/s
Semi-Major Axis6880.00
Stellar Luminosity (Lsun)247.76

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular late- (M
Mean Variability Period in Days0.282
Variable Magnitude Range (Brighter - Dimmer)6.982 - 7.275

Estimated Calculated Facts

Radius (x the Sun)20.49
Effective Temperature4,224 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Comments and Questions

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