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AR Cassiopeiae - HD221253 - HIP115990

AR Cassiopeiae is a blue eclipsing binary system subgiant star that can be located in the constellation of Cassiopeia. HIP115990 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD221253. AR Cassiopeiae has alternative name(s), AR_Cas. AR Cassiopeiae is a multiple star system with 7 stars orbiting in its solar system.

AR Cassiopeiae is one of the biggest multiple star system that we have so far discovered in the milky way. The only other star system that has that many is Jabbah in the constellation of Scorpius. However as the galaxy consists of so many stars and not all have been checked out yet, we may yet find a star system that has more than the seven that this star is believed to have.

Location of AR Cassiopeiae

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 AR Cassiopeiae, the location is 23h 30m 01.92 and +58d32`56.1 .

Proper Motion of AR Cassiopeiae

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 4.15 ± 0.38 miliarcseconds/year towards the north and 17.90 ± 0.52 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of AR Cassiopeiae

AR Cassiopeiae has a spectral type of B3IV. This means the star is a blue subgiant star. The star has a B-V Colour Index of -0.12 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 12,367 Kelvin.

AR Cassiopeiae has been calculated as 3.77 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,623,446.81.km.

AR Cassiopeiae Apparent and Absolute Magnitudes

AR Cassiopeiae has an apparent magnitude of 4.89 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 -1.34 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.51. 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 Cassiopeiae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 5.67 which gave the calculated distance to AR Cassiopeiae as 575.24 light years away from Earth or 176.37 parsecs. It would take a spaceship travelling at the speed of light, 575.24 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 5.25 which put AR Cassiopeiae at a distance of 621.26 light years or 190.48 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 AR Cassiopeiae

The star is a eclipsing binary system Beta Persei (Algol) 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 Cassiopeiae brightness ranges from a magnitude of 5.000 to a magnitude of 5.000 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 6.0 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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

AR Cassiopeiae Facts

Alternative Names

Traditional/Proper NameAR Cassiopeiae
Short NameAR Cas
Hipparcos Library I.D.115990
Bonner DurchmusterungBD+57 2748
Henry Draper Designation221253

Visual Facts

Star Typesubgiant star
Absolute Magnitude-1.34 / -1.51
Apparent Magnitude4.89
Right Ascension (R.A.)23h 30m 01.92
Declination (Dec.)+58d32`56.1
1997 Distance from Earth5.67 Parallax (milliarcseconds)
 575.24 Light Years
 176.37 Parsecs
2007 Revised Distance from Earth5.25 Parallax (milliarcseconds)
 621.26 Light Years
 190.48 Parsecs
Proper Motion Dec.4.15 ± 0.38 milliarcseconds/year
Proper Motion RA.17.90 ± 0.52 milliarcseconds/year
B-V Index-0.12
Spectral TypeB3IV
Colour(B) blue
Stars in Solar System7

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeBeta Persei (Algol)
Mean Variability Period in Days6.000

Estimated Facts

Radius (x the Sun)3.77
Calculated Effective Temperature12,367 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
221253+57 2748.0A4.9000016.000007.00000B3Blue/White
B9.300001947
221237+57 2747.0C7.1000022.0000021.00000A0White1841
CD8.900001841
E8.900001870
F8.900001870
G9.100001914
CH12.900001880

Location of AR Cassiopeiae in Cassiopeia


AR Cassiopeiae Location in Cassiopeia

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


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