Alpha Coronae Borealis (α Coronae Borealis, abbreviated Alpha CrB, α CrB), officially named Alphecca , is an

eclipsing binary A binary star is a system of two stars that are 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 using a telescope as separate stars, in ...

star in the constellation of

Corona Borealis Corona Borealis is a small constellation in the Northern Celestial Hemisphere. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Its brightest stars form a s ...

. It is located about 75

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 Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared rad ...

and contains two

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

stars, one class A and one class G.

Properties

Alpha Coronae Borealis is a binary system, its stars orbiting each other in an

eccentric orbit In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values be ...

every 17.36 days. Because the plane of this orbit is inclined at an angle of 88.2° to the line of sight to the Earth, the pair form a detached eclipsing binary system similar to

Algol ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by th ...

(β Per). The periodic eclipses result in a magnitude variation of +2.21 to +2.32, which is hardly noticeable to the unaided eye. The primary component is a white

star that has a

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 A0V and 2.6 times the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass of ...

. Estimates of the star's radius range from 2.89 to 3.04 times the

radius of the Sun Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: :1\,R_ = 6.9 ...

. An excess of infrared radiation at 24 μm and 70 μm has been detected about the primary star by the

IRAS The Infrared Astronomical Satellite ( Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...

. This suggests the presence of a large disc of

dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in ...

and material around the star, prompting speculation of a planetary or proto-planetary system similar to that currently assumed around

Vega Vega is the brightest star in the northern Northern may refer to the following: Geography * North, a point in direction * Northern Europe, the northern part or region of Europe * Northern Highland, a region of Wisconsin, United Sta ...

. The disk extends out to a radius of around 60 astronomical units (AU). The secondary component is a yellow main sequence star with an estimated stellar class of G5, 0.92 times the Sun's mass and 0.90 times the Sun's radius. The

X-ray X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...

luminosity of this star is , which is 30 times greater than the peak activity level of the Sun. This higher activity level is expected for a young star of this class. The corona has a temperature of about 5 MK, which is much hotter than the Sun's corona. The upper limit of 14 km/s for the equatorial rotation velocity is equivalent to a rotation period of 3 days. More likely, the rotation period is 7–9 days. The space velocity components of this star system are U =, V = and W =. α CrB is believed to be a member of the Ursa Major Moving Group of stars that have a common motion through space.

Nomenclature

''α Coronae Borealis'' ( Latinised to ''Alpha Coronae Borealis'') is the star's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. T ...

. It bore the traditional names ''Alphecca'', ''Gemma'', and ''Gnosia'' (Gnosia Stella Coronae). ''Alphecca'' is

Arabic Arabic (, ' ; , ' or ) is a Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C. E.Watson; Walte ...

, short for ''نير الفكّة'' ''nayyir al-fakka'' "the bright (star) of the broken (ring of stars)". ''Gemma'' is

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

for "jewel". ''Gnosia'' is Greek (from ''γνωσία'' in Hellenistic common and ''γνῶσις'' in ancient Greek, which means ''knowledge''), short for ''Gnōsia stella corōnæ'' "star of the crown of

Knossos Knossos (also Cnossos, both pronounced ; grc, Κνωσός, Knōsós, ; Linear B: ''Ko-no-so'') is the largest Bronze Age archaeological site on Crete and has been called Europe's oldest city. Settled as early as the Neolithic period, the na ...

". ''Asteroth'' is

Hebrew Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...

, עשתרות ‘ašterôt'' "

Astarte Astarte (; , ) is the Hellenized form of the Ancient Near Eastern goddess Ashtart or Athtart (Northwest Semitic), a deity closely related to Ishtar (East Semitic), who was worshipped from the Bronze Age through classical antiquity. The name i ...

(idols)" and mainly referred to the constellation. As the brightest star in Corona Borealis, it lent its name to Alphekka Meridiana, the brightest in the constellation of Corona Australis. The

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize List of proper names of stars, proper names for stars for the international astronomical community. It operates under ...

(WGSN) has chosen ''Alphecca'' as the formal name for this star. The term ''nayyir al-fakka'' or ''Nir al Feccah'' appeared in the Al Achsasi Al Mouakket catalogue. In Chinese, (), meaning '' Coiled Thong'', refers to an asterism consisting of Alpha Coronae Borealis,

Pi Coronae Borealis Pi Coronae Borealis, Latinized from π Coronae Borealis, is a solitary, orange-hued star in the northern constellation of Corona Borealis. Its apparent magnitude is 5.58, which is bright enough to be faintly visible to the naked eye. Base ...

Theta Coronae Borealis Theta Coronae Borealis, Latinized from θ Coronae Borealis, is a binary star system in the constellation Corona Borealis. It shines with a combined apparent visual magnitude (V band) of 4.13. There are two components: Theta Coronae Bore ...

, Beta Coronae Borealis,

Gamma Coronae Borealis Gamma Coronae Borealis, Latinized from γ Coronae Borealis, is a binary star system in the northern constellation of Corona Borealis. It is visible to the naked eye with an apparent visual magnitude of 3.83. Based upon an annual parall ...

Delta Coronae Borealis Delta Coronae Borealis, Latinized from δ Coronae Borealis, is a variable star in the constellation Corona Borealis. Its apparent magnitude varies regularly between apparent magnitude 4.57 and 4.69, and it is around 170 light-years d ...

Epsilon Coronae Borealis Epsilon Coronae Borealis, Latinized from ε Coronae Borealis, is a multiple star system in the constellation Corona Borealis located around 230 light-years from the Solar System. It shines with a combined apparent magnitude of 4.13, me ...

, Iota Coronae Borealis and

Rho Coronae Borealis Rho Coronae Borealis (ρ CrB, ρ Coronae Borealis) is a yellow dwarf star 56 light-years away in the constellation of Corona Borealis. The star is thought to be similar to the Sun with nearly the same mass, radius, and luminosity. It ...

. 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 Alpha Coronae Borealis itself is (, en, the Fourth Star of Coiled Thong.).

References

{{DEFAULTSORT:Alpha Coronae Borealis G-type main-sequence stars A-type main-sequence stars Eclipsing binaries Ursa Major Moving Group Alphecca Corona Borealis Coronae Borealis, Alpha Durchmusterung objects Coronae Borealis, 05 139006 076267 5793