AR Cassiopeiae (AR Cas) is a
variable star
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...
in the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The first constellati ...
of
Cassiopeia
Cassiopeia or Cassiopea may refer to:
Greek mythology
* Cassiopeia (mother of Andromeda), queen of Aethiopia and mother of Andromeda
* Cassiopeia (wife of Phoenix), wife of Phoenix, king of Phoenicia
* Cassiopeia, wife of Epaphus, king of Egy ...
. It is thought to be a member of a
septuple star system, one of only two known
star system
A star system or stellar system is a small number of stars that orbit each other, bound by gravity, gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally calle ...
s with a multiplicity of 7, the other being
Nu Scorpii
Nu Scorpii (ν Scorpii, abbreviated Nu Sco, ν Sco) is a star system, multiple star system in the constellation of Scorpius. It is most likely a septuple star system, consisting of two close groups (designated Nu Scorpii AB and CD) tha ...
.
[
]
Nomenclature
The multiple star system as a whole has the designations ADS 16795, CCDM J23300+5833, and WDS J23300+5833AB in the Aitken Double Star Catalogue The Aitken Double Star Catalogue, or ADS, is a star catalogue of double stars. It was compiled by Robert Grant Aitken and published in 1932 in two volumes, under the name ''New general catalogue of double stars within 120° of the North Pole''. It ...
, the Catalogue of Components of Double and Multiple Stars
The Catalog of Components of Double and Multiple Stars, or CCDM, is an astrometric star catalogue of double and multiple stars. It was made by Jean Dommanget and Omer Nys at the Royal Observatory of Belgium in order to provide an input catalogue ...
, and the Washington Double Star Catalog
The Washington Double Star Catalog, or WDS, is a catalog of double stars, maintained at the United States Naval Observatory. The catalog contains positions, magnitudes, proper motions and spectral types and has entries for (as of January 2024) 1 ...
respectively.[
AR Cassiopeiae has been referred to as IH Cas in some literature, looking similar to a ]variable star designation
In astronomy, a variable-star designation is a unique identifier given to variable stars. It extends the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in whic ...
although not a valid one since the second letter of a variable star designation is always equal to the first or occurs later in the alphabet. The origin of the designation "IH Cassiopeiae" is from the 17th century catalogue and constellation map by Johannes Hevelius
Johannes Hevelius
Some sources refer to Hevelius as Polish:
*
*
*
*
*
*
*
Some sources refer to Hevelius as German:
*
*
*
*
*of the Royal Society
* (in German also known as ''Hevel''; ; – 28 January 1687) was a councillor and mayor of Danz ...
, which was kept in use due to the lack of a Flamsteed designation
A Flamsteed designation is a combination of a number and constellation name that uniquely identifies most naked eye stars in the 88 modern constellations, modern constellations visible from southern England. They are named after John Flamsteed, au ...
or Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...
for the star.[ thus "1 Hev. Cas" or "1 H. Cas" (similar to ]Gould designation Gould designations for stars are similar to Flamsteed designations in the way that they number stars within a constellation in increasing order of right ascension. Each star is assigned an integer (starting at 1), followed by " G. " (or occasionall ...
s), which becomes IH Cas through corruption.[
]
Properties
The primary star system, AR Cassiopeiae, is a triple. AR Cassiopeiae B is located 0.800″ away from AR Cassiopeiae A.[
In 1921, Joel Stebbins announced that observations from 1917 through 1921 had shown that the star is an ]eclipsing binary
A binary star or binary star system is a Star system, system of two stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved ...
.orbital period
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...
of about 6.07 days.[ Its primary is a ]B-type main-sequence star
A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. B-type stars ...
, and the secondary an A-type main-sequence star
An A-type main-sequence star (A) or A dwarf star is a main-sequence (hydrogen burning) star of spectral type A and luminosity class (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...
. The secondary star may be an Am star
An Am star or metallic-line star is a type of chemically peculiar star of spectral type A whose spectrum has strong and often variable absorption lines of metals such as zinc
Zinc is a chemical element; it has symbol Zn and atomic number 30. ...
.[
Farther out are two other stars, designated components C and D. They are 76.1″, or about 1.27′, away from the central system.][ Their combined ]spectrum
A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...
matches that of another B-type main-sequence star.[ This pair is also designated HD 221237.][ 67.2″ (1.12′) away from AR Cassiopeiae is another pair of stars, F and G, both ]F-type star
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...
s.[
All these stars are known to be common ]proper motion
Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...
companions.[ However, the star listed as component E in most multiple star catalogues is an unrelated background star.
]
References
{{Stars of Cassiopeia
Cassiopeia (constellation)
Algol variables
7
Cassiopeiae, AR
Durchmusterung objects
221253
8926
115990
B-type main-sequence stars