star
A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...
parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby object ...
shift of 38.17
mas
Mas, Más or MAS may refer to:
Film and TV
* Más y Menos, fictional superhero characters, from the Teen Titans animated television series
* Más (Breaking Bad), "Más" (''Breaking Bad''), a season three episode of ''Breaking Bad''
Songs
* Más ( ...
as seen from the Earth, it is located about 85
light year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s from the Sun. The star is visible to the naked eye with an
apparent visual magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...
stellar classification
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 t ...
of or F0 IV. Thus it may either be an
F-type main sequence
An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K.Tables VII ...
star showing an abundance excess of strontium, or it could be a more
evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation te ...
subgiant star
A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...
. It is a Delta Scuti variable star that cycles between magnitudes 4.15 and 4.21 every 59.388 minutes. The star displays an
infrared excess
An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are ofte ...
, indicating the presence of a
debris disk
A debris disk (American English), or debris disc (Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris di ...
with a temperature of 65 K orbiting at a radius of 62 AU. This dust has a combined mass equal to 6.6% of the Earth's mass.
Binary
There is a faint companion star at an
angular separation
Angular distance \theta (also known as angular separation, apparent distance, or apparent separation) is the angle between the two sightlines, or between two point objects as viewed from an observer.
Angular distance appears in mathematics (in pa ...
of along a
position angle
In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the north celestial pole (NCP), turning positive into the ...
of . This corresponds to a projected physical separation of . The probability of a random star being situated this close to Epsilon Cephei is about one in a million, so it is most likely physically associated. If so, then the debris disk is probably circumbinary. The fact that this companion was not detected during the
Hipparcos
''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...
mission may indicate its orbit has a high eccentricity. The companion star has a K-band magnitude of 7.8 and is probably of class K8–M2.
Naming
In Chinese, (), meaning '' Flying Serpent'', refers to an asterism consisting of ε Cephei,
α Lacertae
Alpha Lacertae, Latinised from α Lacertae, is a single white-hued star in the constellation of Lacerta, located 103 light-years from the Sun. It is the brightest star in Lacerta with an apparent visual magnitude of 3.76. ...
,
4 Lacertae
4 Lacertae is a single star in the northern constellation Lacerta, located about 1,900 light years away. This object visible to the naked eye as a white-hued star with an apparent visual magnitude of 4.55. It is moving closer to th ...
β Lacertae
Beta Lacertae (Beta Lac, β Lacertae, β Lac) is the fourth-brightest star in the constellation of Lacerta. Based upon an annual parallax shift of 19.19 mas, it is 170 light-years distant from Earth. At tha ...
,
σ Cassiopeiae
Sigma Cassiopeiae (σ Cas, σ Cassiopeiae) is a binary star in the constellation Cassiopeia. It is 1,200 to from Earth and has a combined apparent magnitude of +4.88.
The primary component, σ Cassiopeiae A, is a B2 subgiant with ...
9 Lacertae
9 Lacertae is a single star in the northern constellation Lacerta, located 172 light years away from Sun. It is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of 4.64. This object is moving furt ...
,
3 Andromedae
3 Andromedae, abbreviated 3 And, is a single star in the northern constellation of Andromeda. ''3 Andromedae'' is the Flamsteed designation. It is visible to the naked eye with an apparent visual magnitude of 4.64. The distance to this ...
,
7 Andromedae
7 Andromedae (abbreviated 7 And) is a single, yellow-white hued star in the northern constellation of Andromeda. ''7 Andromedae'' is the Flamsteed designation. It is visible to the naked eye with an apparent visual magnitude of 4.52, and ...
,
8 Andromedae
8 Andromedae, abbreviated 8 And, is a probable triple star system in the northern constellation of Andromeda. ''8 Andromedae'' is the Flamsteed designation. It is visible to the naked eye with an apparent visual magnitude of 4.82. Based ...
,
λ Andromedae
Lambda Andromedae, Latinized from λ Andromedae, is the Bayer designation for a binary star system in the northern constellation of Andromeda. At an estimated distance of approximately from Earth, it has an apparent visual magnitude o ...
ψ Andromedae
Psi Andromedae (ψ And, ψ Andromedae) is the Bayer designation for a triple star system in the northern constellation of Andromeda. The combined apparent visual magnitude of this system is 4.95. Based upon parallax measurements, is rou ...
. Consequently, the
Chinese name
Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are oft ...
for ε Cephei itself is (, en, the Ninth Star of Flying Serpent)