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 w ...

star 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 origins of the e ...

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 se ...

. It is located about 75 light years 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 radi ...

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 A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that th ...

, 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 betw ...

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 the ...

(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 stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

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 ...

. 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_ = 6.957\t ...

. 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 homes ...

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 constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, an ...

. 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 An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

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 Corona (from the Latin for 'crown') most commonly refers to: * Stellar corona, the outer atmosphere of the Sun or another star * Corona (beer), a Mexican beer * Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...

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. ...

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

Arabic Arabic (, ' ; , ' or ) is a Semitic languages, 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 ...

, 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 of the ...

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 Corona Australis is a constellation in the Southern Celestial Hemisphere. Its Latin name means "southern crown", and it is the southern counterpart of Corona Borealis, the northern crown. It is one of the 48 constellations listed by the 2nd-centu ...

. 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, outreac ...

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 proper names for stars for the international astronomical community. It operates under Division C – Education ...

(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, Theta Coronae Borealis,

Beta Coronae Borealis Beta Coronae Borealis (β Coronae Borealis, abbreviated Beta CrB, β CrB) is a binary star in the constellation of Corona Borealis. It appears to the naked eye to be a single star and is the second-brighte ...

, Gamma Coronae Borealis, Delta Coronae Borealis, Epsilon Coronae Borealis,

Iota Coronae Borealis Iota Coronae Borealis, Latinized from ι Coronae Borealis, is a binary star system in the constellation Corona Borealis. It is visible to the naked eye with a combined apparent visual magnitude of is 4.96. Based upon an annual parallax ...

and Rho Coronae Borealis. 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 often a ...

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