In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, (), meaning "Snake's Head", refers to an asterism consisting of α Hydri and β Reticuli. Consequently, α Hydri itself is known as (, .)
Naming
Alpha Hydri
Alpha Hydri | Naming
Chinese system Meaning "Snake's Head", refers to an asterism consisting of α Hydri and β Reticuli. Chinese In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, meaning "Snake's Head", refers to an asterism consisting of α Hydri and β Reticuli.
what is hydrus?
user
Small constellation in the deep southern sky.
assistant
what are its characteristics?
user
Irregular in shape and its tail has been shortened to make space for this last constellation he had drawn up.
assistant
name a few stars in the constellation?
user
Beta Hydri, Alpha Hydri, etc.
assistant
where did the second star get its name from?
user
Alpha Hydri (α Hyi, α Hydri) is the second brightest star in the southern circumpolar constellation of Hydrus. It is readily visible to the naked eye with an apparent visual magnitude of +2.9. It is sometimes informally known as the Head of Hydrus. This should not be confused with Alpha Hydrae (Alphard) in the constellation Hydra. Alpha Hydri is one of only three stars in the constellation Hydrus that are above the fourth visual magnitude. This star can be readily located as it lies to the south and west of the prominent star Achernar in the constellation Eridanus. Based upon parallax measurements from the Hipparcos mission, Alpha Hydri is located at a distance of about from Earth.
Alpha Hydri | Introduction
"β Ceti" (Latinised to "Beta Ceti") is the star's Bayer designation. It bore the traditional names "Diphda" and "Deneb Kaitos" . "Diphda" is Arabic for 'frog', from the phrase ضفدع الثاني" "aḍ-ḍifdaʿ aṯ-ṯānī" 'the second frog' (the first frog' is Fomalhaut); "Deneb Kaitos" is from الذنب القيتوس الجنوب "Al Dhanab al Ḳaiṭos al Janūbīyy" 'southern tail of Cetus'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name "Diphda" for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
Beta Ceti | Nomenclature
A line drawn between Alpha Hydri and Beta Centauri is bisected by the south celestial pole.
Hydrus | Stars
Keyzer and de Houtman assigned fifteen stars to the constellation in their Malay and Madagascan vocabulary, with a star that would be later designated as Alpha Hydri marking the head, Gamma the chest and a number of stars that were later allocated to Tucana, Reticulum, Mensa and Horologium marking the body and tail. Lacaille charted and designated 20 stars with the Bayer designations Alpha through to Tau in 1756. Of these, he used the designations Eta, Pi and Tau twice each, for three sets of two stars close together, and omitted Omicron and Xi. He assigned Rho to a star that subsequent astronomers were unable to find.
Hydrus | Stars
Beta Hydri (β Hyi, β Hydri) is a star in the southern circumpolar constellation of Hydrus. (Note that Hydrus is not the same as Hydra.) With an apparent visual magnitude of 2.8, this is the brightest star in the constellation. Based upon parallax measurements the distance to this star is about . This star has about 104% of the mass of the Sun and 181% of the Sun's radius, with more than three times the Sun's luminosity. The spectrum of this star matches a stellar classification of G2 IV, with the luminosity class of 'IV' indicating this is a subgiant star.
Beta Hydri | Introduction
It is now so entered in the IAU Catalog of Star Names. The European astronomer Tycho Brahe dubbed it "Cor Hydræ", Latin for 'the heart of Hydra'.
Alphard | Nomenclature
"δ Sagittarii" (Latinised to "Delta Sagittarii") is the star's Bayer designation. It bore the traditional names "Kaus Media", "Kaus Meridionalis", and "Media", which derive from the ('bow') and ('middle'). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Kaus Media" for this star. In the catalogue of stars in the "Calendarium" of Al Achsasi al Mouakket, this star was designated , meaning 'second of Warida'.
Delta Sagittarii | Nomenclature
In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, (), meaning "Snake's Head", refers to an asterism consisting of α Hydri and β Reticuli. Consequently, α Hydri itself is known as (, .)
Alpha Hydri | Naming
The Bayer designation Eta Hydri (η Hyi / η Hydri) is shared by two stars, in the constellation Hydrus:
Eta Hydri | Introduction
"Hydor" is from Greek Ὕδωρ "water", a name given by Proclus, according to Richard Hinckley Allen. Another Greek name for the star is "Ekkhysis", from εκχυσις "outpouring". In Chinese, (), meaning "Line of Ramparts", refers to an asterism consisting of λ Aquarii, κ Capricorni, ε Capricorni, γ Capricorni, δ Capricorni, ι Aquarii, σ Aquarii, φ Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium. Consequently, λ Aquarii itself is (, .)
Lambda Aquarii | Naming
As such, it is a slightly more evolved star than the Sun, with the supply of hydrogen at its core becoming exhausted. It is one of the oldest stars in the solar neighborhood. This star bears some resemblance to what the Sun might look like in the far distant future, making it an object of interest to astronomers.
Beta Hydri | Introduction
Consequently, the Chinese name for ρ Scorpii itself is (), "the Second Star of Room".
Rho Scorpii | Nomenclature
Thought to be between 6.4 and 7.1 billion years old, this star bears some resemblance to what the Sun may look like in the far distant future, making it an object of interest to astronomers. It is also the closest bright star to the south celestial pole. Located at the northern edge of the constellation and just southwest of Achernar is Alpha Hydri, a white sub-giant star of magnitude 2.9, situated 72 light-years from Earth. Of spectral type F0IV, it is beginning to cool and enlarge as it uses up its supply of hydrogen. It is twice as massive and 3.3 times as wide as our sun and 26 times more luminous.
Hydrus | Stars
Eta Hydri (η Hyi, η Hydri), often catalogued as HD 11977, is a giant yellow star approximately 219 light-years away in the constellation of Hydrus. Based on its mass, it was probably a class A star (similar to Vega or Fomalhaut) when it was on the main sequence, though it is now in the giant stage of its evolution. It is thought to be around 1.3 billion years old and has expanded to 10 times the Sun's diameter, though is only around 1.8 times as massive as the Sun. As of 2005, an extrasolar planet was confirmed to be orbiting the star.
Eta2 Hydri | Introduction
Alpha Aquarii (α Aquarii, abbreviated Alpha Aqr, α Aqr), officially named Sadalmelik , is a single star in the constellation of Aquarius. The apparent visual magnitude of 2.94 makes this the second-brightest star in Aquarius. Based upon parallax measurements made during the Hipparcos mission, it is located at a distance of roughly from the Sun. It forms the primary or 'A' component of a double star designated WDS J22058-0019 (the secondary or 'B' component is UCAC2 31789179).
Alpha Aquarii | Introduction
According to a 1971 NASA catalogue, "al-Nasaq al-Yamānī" or "Nasak Yamani" was the name for two stars: Delta Serpentis as "Nasak Yamani I" and Epsilon Serpentis as "Nasak Yamani II".
Alpha Serpentis | Nomenclature
Few of those designations have survived. It is worth mentioning, however, as it served as the starting point for variable star designations, which start with "R" through "Z", then "RR", "RS", "RT"..."RZ", "SS", "ST"..."ZZ" and beyond. The second system comes from the English astronomer John Flamsteed's "Historia coelestis Britannica" (1725). It kept the genitive-of-the-constellation rule for the back end of his catalogue names, but used numbers instead of the Greek alphabet for the front half. Examples include 61 Cygni and 47 Ursae Majoris.
Star catalogue | Bayer and Flamsteed catalogues
However, this may have been based on a photographic plate that was later rejected. It is listed in the General Catalogue of Variable Stars, but marked as probably constant. The star is about 311 million years old and is radiating 91 times the luminosity of the Sun from its photosphere at an effective temperature of 9,816 K.
Eta1 Hydri | Introduction
"α Aquarii" (Latinised to "Alpha Aquarii") is the star's Bayer designation. WDS J22058-0019 A is its designation in the Washington Double Star Catalog. It bore the traditional name "Sadalmelik", which derived from an Arabic expression سعد الملك ("sa‘d al-malik"), meaning "Luck of the king". The name "Rucbah" had also been applied to this star; though it shared that name with Delta Cassiopeiae. It is only one of two stars with ancient proper names to lie within a degree of the celestial equator. The origin of the Arabic name is lost to history. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars.
Alpha Aquarii | Nomenclature
In the catalogue of stars in the "Calendarium of Al Achsasi Al Mouakket", this star was designated Thanih al Adzari (ثاني ألعذاري - "thaanii al-aðārii"), which was translated into Latin as Secunda Virginum, meaning "the second virgin". This star, along with ε CMa (Adhara), δ CMa (Wezen) and η CMa (Aludra), were Al ʽAdhārā (ألعذاري), the Virgins.
Omicron2 Canis Majoris | Name
ν Hydri, Latinized as Nu Hydri, is a single star in the southern circumpolar constellation of Hydrus. It is orange-hued and faintly visible to the naked eye with an apparent visual magnitude of 4.76. This object is located approximately 331 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +3 km/s. It is a member of the Ursa Major Moving Group of stars that share a common motion through space. This is an aging giant star with a stellar classification of K3III. With the supply of hydrogen at its core exhausted, the star has expanded and cooled.
Nu Hydri | Introduction
This is the list of notable stars in the constellation Hydrus, sorted by decreasing brightness.
List of stars in Hydrus | Introduction
The Chinese name for the star is 马腹一 (Mandarin: mǎ fù yī, "the First Star of the Horse's Abdomen").
Beta Centauri | Nomenclature
"δ¹ Tauri" (Latinised to "Delta¹ Tauri") is the system's Bayer designation. The designations of the two constituents as "Delta¹ Tauri A" and "B", and those of "A's" components - "Delta¹ Tauri Aa" and "Ab" - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). The system bore the traditional name "Hyadum II", which is Latin for "Second of the Hyades". In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.
Delta1 Tauri | Nomenclature
"α Cancri" (Latinised to "Alpha Cancri") is the star's Bayer designation. The traditional name "Acubens" (Açubens) is derived from the Arabic , "the claws" A second name, Sertan , derives from the Arabic "al-saraṭān" 'the crab'. The International Astronomical Union Working Group on Star Names (WGSN) choose 'Acubens' as the proper name for this star.
Alpha Cancri | Nomenclature
In the catalogue of stars in the "Calendarium" of Al Achsasi al Mouakket, this star was designated "Thanih Saad al Saaoud" ( – ), which was translated into Latin as , meaning "the second of luck of lucks". This star, along with Beta Aquarii and 46 Capricorni, were (), "the Luck of Lucks".
Xi Aquarii | Nomenclature
This star, along with the "Aselli" (Theta Boötis, Iota Boötis and Kappa Boötis), were "Al Aulād al Dhiʼbah" (ألعولد ألذعب - "al aulād al dhiʼb"), "the Whelps of the Hyenas". "Al Aulād al Dhiʼbah" or "Aulad al Thiba" was the title of this star in a 1971 NASA memorandum.
Lambda Boötis | Nomenclature
Eventually the Reverend Thomas Webb, a British astronomer, puzzled out the explanation. Cacciatore's name, "Nicholas Hunter" in English translation, would be Latinized to "Nicolaus Venator". Reversing the letters of this construction produces the two names. They have endured, the result of Cacciatore's little practical joke of naming the two after himself. How Webb arrived at this explanation 45 years after the publication of the catalogue is still a mystery. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.
Beta Delphini | Nomenclature
"α Hydrae" (Latinised to "Alpha Hydrae") is the star's Bayer designation. The traditional name "Alphard" is from the Arabic الفرد ("al-fard"), "the solitary one", there being no other bright stars near it. It was also known as the "backbone of the Serpent" to the Arabs. In the catalogue of stars in the "Calendarium of Al Achsasi Al Mouakket", it was designated "Soheil al Fard", which was translated into Latin as "Soheil Solitarius", meaning "the bright solitary one". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Alphard" for this star.
Alphard | Nomenclature
Alpha Capricorni is known as 牛宿二 (the Second Star of the Ox) in Chinese astronomy.
Alpha Capricorni | Nomenclature
Consequently, the Chinese name for β Leporis itself is (), "the Second Star of Toilet".
Beta Leporis | Nomenclature
"θ Columbae", Latinised to "Theta Columbae", is the star's Bayer designation. Early Arab poets referred to a number of anonymous stars as الفرود "al-furūd", "the solitary ones". Later Arabian astronomers attempted to identify this name with particular stars, principally in the modern constellations Centaurus and Colomba. Allen (1899) noted the accepted etymology but suggested that "al-furūd" might have been an old transcriber's error for القرود‎ "al-qurūd" "the apes", which he rendered "Al Ḳurūd", though this suggested has not received scholarly support. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars.
Theta Columbae | Nomenclature
("Crater" is abbreviated "Crt" to prevent confusion with "CrA".) When letters are taken from the second word of a two-word name, the first letter from the second word is capitalised: "CMa" for "Canis Major", "CMi" for "Canis Minor". Two cases are ambiguous: "Leo" for the constellation "Leo" could be mistaken for "Leo Minor" (abbreviated "LMi"), and "Tri" for "Triangulum" could be mistaken for "Triangulum Australe" (abbreviated "TrA").
IAU designated constellations | Abbreviations
Beta Hydri, the brightest star in Hydrus, is a yellow star of apparent magnitude 2.8, lying 24 light-years from Earth. It has about 104% of the mass of the Sun and 181% of the Sun's radius, with more than three times the Sun's luminosity. The spectrum of this star matches a stellar classification of G2 IV, with the luminosity class of 'IV' indicating this is a subgiant star. As such, it is a slightly more evolved star than the Sun, with the supply of hydrogen fuel at its core becoming exhausted. It is the nearest subgiant star to the Sun and one of the oldest stars in the solar neighbourhood.
Hydrus | Stars
"ε Sagittarii" (Latinised to "Epsilon Sagittarii") is the star system's Bayer designation. It bore the traditional name "Kaus Australis", which derived from the Arabic قوس "qaws" 'bow' and Latin "austrālis" 'southern'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Kaus Australis" for the star ε Sagittarii A. In the catalogue of stars in the "Calendarium" of Al Achsasi al Mouakket, this star was designated "Thalath al Waridah", or "Thalith al Waridah", meaning 'third of Warida'.
Epsilon Sagittarii | Nomenclature
The WGSN states that in the case of multiple stars the name should be understood to be attributed to the brightest component by visual brightness. The WGSN approved the names "Arkab Prior" and "Arkab Posterior" for "β Sagittarii A" and "β Sagittarii" on 5 October 2016 and they are now so entered in the IAU Catalog of Star Names. "β" and "β Sagittarii", together with Alpha Sagittarii, were "Al Ṣuradain" (الصردين), the two "Surad", "desert birds".
Beta Sagittarii | Nomenclature
With φ, κ, κ and χ, it composed the Arabic were the Arabs' "Al Kalbain", the Two Dogs. According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Al Kalbain" were the title for five stars : φ as "Alkalbain I", χ as "Alkalbain II", κ as "Alkalbain III", κ as "Alkalbain IV" and this star (υ) as "Alkalbain V".
Upsilon Tauri | Naming
It has been speculated that this star is part of the second generation, born out of the gas clouds which were imbued with elements such as carbon by the primordial Population III stars.
HE 1327-2326 | Introduction
There is a nearby companion star of class A0 IV located at an angular separation of 0.1 arc seconds along a position angle of 179°, as of 2002. Schöller et al. (2010) consider this to be a visual companion, although Eggleton and Tokovinin (2008) listed the pair as a probable binary star system.
Theta Hydri | Introduction
"β Centauri" (Latinised to "Beta Centauri") is the star system's Bayer designation. It bore the traditional names "Hadar" and "Agena". "Hadar" comes from the Arabic حضار (the root's meaning is "to be present" or "on the ground" or "settled, civilized area"), while the name "Agena" is thought to be derived from the Latin "genua", meaning "knees", from the star's position on the left knee of the centaur depicted in the constellation Centaurus. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name "Hadar" for the star β Centauri Aa on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
Beta Centauri | Nomenclature
"ζ Aurigae" (Latinised to "Zeta Aurigae") is the system's Bayer designation. The designations of the two components as "ζ Aurigae A" and "B" derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). The system bore the traditional names "Haedus I" (also "Hoedus") and "Sadatoni" (rarely "Saclateni"). It was one of the two "haedi" (Latin: 'kids') of the she-goat Capella, the other being Haedus II, Eta Aurigae. The name Sadatoni is from the Arabic الساعد الثاني "as-sāid aθ-θānī" "the second arm (of the charioteer)". The rare traditional name "Azaleh" is shared (in the form "Hassaleh") with Iota Aurigae.
Zeta Aurigae | Nomenclature
"β Lyrae" (Latinised to "Beta Lyrae") is the system's Bayer designation, established by Johann Bayer in his "Uranometria" of 1603, and denotes that it is the second brightest star in the Lyra constellation. WDS J18501+3322 is a designation in the Washington Double Star Catalog. The designations of the constituents as "Beta Lyrae A", "B" and "C", or alternatively "WDS J18501+3322A", "B" and "C", and additionally "WDS J18501+3322D", "E" and "F", and those of "A's" components - "Beta Lyrae Aa", "Aa1", "Aa2" and "Ab" - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
Beta Lyrae | Nomenclature
It spent much of its stellar life as a B-type main sequence star before expanding and cooling to its current state as it spent its core hydrogen. The secondary is a white main sequence star of spectral type A3V and magnitude 6.57. Despite having different distances when measured by the HIPPARCOS satellite, the two stars share a common proper motion and appear to be a natural binary system.
Cancer (constellation) | Stars
Eta Hydri b (η Hyi b, η Hydri b), commonly known as HD 11977 b, is an extrasolar planet that is approximately 217 light-years away in the constellation of Hydrus. The presence of the planet around an intermediately massive giant star provides indirect evidence for the existence of planetary systems around A-type stars.
Eta2 Hydri b | Introduction
This subgiant star is 80% larger and twice as massive as the Sun, with a stellar classification of F0 IV. It is about 810 million years old and is radiating 32 times the Sun's luminosity from its outer atmosphere at an effective temperature of 7,077 K. Alpha Hydri emits X-rays similar to Altair. The space velocity components of this star are [U, V, W] = .
Alpha Hydri | Introduction
Three stars make up the long narrow triangle that gives the constellation its name. The brightest member is the white giant star Beta Trianguli of apparent magnitude 3.00, lying 127 light-years distant from Earth. It is actually a spectroscopic binary system; the primary is a white star of spectral type A5IV with 3.5 times the mass of our sun that is beginning to expand and evolve off the main sequence. The secondary is poorly known, but calculated to be a yellow-white F-type main-sequence star around 1.4 solar masses. The two orbit around a common centre of gravity every 31 days, and are surrounded by a ring of dust that extends from 50 to 400 AU away from the stars.
Triangulum | Stars
"β Aurigae" is the star system's Bayer designation. The traditional name "Menkalinan" is derived from the Arabic منكب ذي العنان "mankib ðī-l-‘inān" "shoulder of the rein-holder". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Menkalinan" for this star. It is known as 五車三 (the Third Star of the Five Chariots) in traditional Chinese astronomy.
Beta Aurigae | Nomenclature
Though, according to a 1971 NASA catalog, "al-Nasaq al-Sha'āmī" or "Nasak Shamiya" was the title for three other stars: Beta Serpentis as "Nasak Shamiya I", Gamma Serpentis as "Nasak Shamiya II" and Gamma Herculis as "Nasak Shamiya III".
Beta Herculis | Nomenclature
Theta Hydri, Latinized from θ Hydri, is the Bayer designation for a blue-white hued star in the southern constellation of Hydrus. It is faintly visible to the naked eye with an apparent visual magnitude of +5.53. Based upon an annual parallax shift of 6.34 mas as seen from Earth, is located roughly 510 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction of 0.10 due to interstellar dust. It is moving away from the Sun with a radial velocity of +12.3 km/s. A stellar classification of B8 III/IV suggests it is an evolving B-type star showing mixed traits of a subgiant or giant star.
Theta Hydri | Introduction
Eventually the Reverend Thomas Webb, a British astronomer, puzzled out the explanation. Cacciatore's name, "Nicholas Hunter" in English translation, would be Latinized to "Nicolaus Venator". Reversing the letters of this construction produces the two star names. They have endured, the result of Cacciatore's little practical joke of naming the two stars after himself. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name "Sualocin" for the component Alpha Delphini Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.
Alpha Delphini | Nomenclature
The spectral class of the primary is A5. Hermann Carl Vogel determined that Sheratan was a spectroscopic binary in 1903; its orbit was determined by Hans Ludendorff in 1907. It has since been studied for its eccentric orbit. γ Arietis, with a common name of Mesarthim, is a binary star with two white-hued components, located in a rich field of magnitude 8–12 stars. Its traditional name has conflicting derivations. It may be derived from a corruption of "al-sharatan", the Arabic word meaning "pair" or a word for "fat ram". However, it may also come from the Sanskrit for "first star of Aries" or the Hebrew for "ministerial servants", both of which are unusual languages of origin for star names.
Aries (constellation) | Stars
This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and ζ Aqr (Sadaltager / Achr al Achbiya), were "al Aḣbiyah" (الأخبية), the Tent. In Chinese, (), meaning "Tomb", refers to an asterism consisting of η Aquarii, γ Aquarii, ζ Aquarii, π Aquarii. Consequently, the Chinese name for η Aquarii itself is (, .)
Eta Aquarii | Naming
Delta Hydri, Latinized from δ Hydri, is a single, white-hued star in the southern constellation of Hydrus. It is bright enough to be faintly visible to the naked eye with an apparent visual magnitude of 4.09. The distance to this star, based upon an annual parallax shift of 23.35 mas, is about 140 light years. It is moving away from the Sun with a radial velocity of +6 km/s. This is an ordinary A-type main-sequence star with a stellar classification of A2 V It is about 209 million years old and has a high rate of spin, showing a projected rotational velocity of 162 km/s.
Delta Hydri | Introduction
Eta Hydri, Latinized from η Hydri, is a blue-white hued star in the southern constellation of Hydrus. It has an apparent visual magnitude of 6.76, which may be too faint to be visible to the naked eye. Based upon an annual parallax shift of as measured from Earth, the system is located about 619 light years distant from the Sun. At that distance, the visual magnitude of the star is diminished by 0.10 magnitudes of extinction due to interstellar dust. The star is drifting further away with a heliocentric radial velocity of +15 km/s. This is a B-type main-sequence star with a stellar classification of B9 V that was suspected in 1939 by Herbert Schneller of being variable.
Eta1 Hydri | Introduction
Epsilon Hydri, Latinized from ε Hydri, is a single, blue-white hued star in the southern constellation of Hydrus. It is a faint star with an apparent visual magnitude of 4.12, but it can be seen with the naked eye. Measurements made by the Hipparcos spacecraft showed an annual parallax shift of 21.48 mas, which provides a distance estimate of 152 light years. The star is moving away from the Sun with a radial velocity of +13.6 km/s. It is a member of the Tucana-Horologium moving group, an association of stars that share a common motion through space. The stellar classification for this star is B9 Va, indicating that is it a B-type main-sequence star that is generating energy through hydrogen fusion at its core.
Epsilon Hydri | Introduction
"α² Capricorni" (Latinised to "Alpha² Capricorni") is the star's Bayer designation. It bore the traditional names "Secunda Giedi" or "Algiedi Secunda" and shared the name "Algedi" (from the Arabic "الجدي" "al-jadii" 'the goat') with α¹ Capricorni. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name "Algedi" for "α² Capricorni" on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names. In Chinese, (), meaning "Ox (asterism)", refers to an asterism consisting of α² Capricorni, Beta Capricorni, ξ² Capricorni, Pi Capricorni, Omicron Capricorni and Rho Capricorni.
Alpha2 Capricorni | Nomenclature
In the catalogue of stars in the "Calendarium of Al Achsasi Al Mouakket", this star was designated Thanih al Naamat (ثاني النعامات - "thānī al-naʽāmāt"), which was translated into Latin as Secunda Struthionum, meaning "the second ostrich". This star, along with η Cet (Deneb Algenubi), τ Cet (Thalath Al Naamat), ζ Cet (Baten Kaitos)and υ Cet, were Al Naʽāmāt (النعامات), the Hen Ostriches. In Chinese, (), meaning "Square Celestial Granary", refers to an asterism consisting of θ Ceti, ι Ceti, η Ceti, ζ Ceti, τ Ceti and 57 Ceti. Consequently, the Chinese name for θ Ceti itself is (, .)
Theta Ceti | Name
Beta Tauri (Latinised from β Tauri, abbreviated Beta Tau, β Tau), officially named Elnath (pronounced or , sometimes spelled "Alnath"), is the second-brightest star located in the constellation borders of Taurus and Auriga with an apparent magnitude of 1.65. It is a chemically peculiar B7 giant star, 134 light years away from Earth. It had a co-existing name Gamma Aurigae.
Beta Tauri | Introduction
A third name that has been applied is "Bungula" (), of obscure origin. Allen can only surmise it may have been coined from the Greek letter beta (β) and Latin 'hoof'.
Alpha Centauri | Nomenclature
"β Aquilae" (Latinised to "Beta Aquilae") is the system's Bayer designation. The designations of the two components as "Beta Aquilae A" and "B" derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). The system bore the traditional name "Alshain" derived from the Perso-Arabic term الشاهين, "aš-šāhīn", meaning "the (peregrine) falcon", perhaps by folk etymology from the Persian "šāhīn tarāzū" (or possibly "šāhīn tara zed"; see Gamma Aquilae), the Persian name for the asterism α, β and γ Aquilae. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars.
Beta Aquilae | Nomenclature
In a given constellation, the first variable stars discovered were designated with letters R through Z, e.g. R Andromedae. This system of nomenclature was developed by Friedrich W. Argelander, who gave the first previously unnamed variable in a constellation the letter R, the first letter not used by Bayer. Letters RR through RZ, SS through SZ, up to ZZ are used for the next discoveries, e.g. RR Lyrae. Later discoveries used letters AA through AZ, BB through BZ, and up to QQ through QZ (with J omitted). Once those 334 combinations are exhausted, variables are numbered in order of discovery, starting with the prefixed V335 onwards.
Variable star | Nomenclature
The name "Hadar" comes from the GUCCCo. Star Class boats being named after stars or constellations. "Hadar" is more commonly known as "Beta Centauri" and is the tenth-brightest star in the night sky. It is in the southern hemisphere and part of the Centaurus constellation and one of the two stars that point to the Southern Cross.
Hadar (narrowboat) | Name
Chinese constellation) consisting of Epsilon Scorpii, Mu¹ Scorpii, Zeta¹ Scorpii and Zeta² Scorpii, Eta Scorpii, Theta Scorpii, Iota² Scorpii and Iota¹ Scorpii, Kappa Scorpii, Lambda Scorpii and Upsilon Scorpii. Consequently, the name for Epsilon Scorpii itself is (), which means "the Second Star of Tail".
Epsilon Scorpii | Nomenclature
As a consequence, the constellation is no longer visible from subtropical northern latitudes, as it was in the time of the ancient Greeks. Around 200 BC, the star Beta Hydri was the nearest bright star to the Celestial south pole. Around 2800 BC, Achernar was only 8 degrees from the south pole.
Pole star | Southern pole star (South Star)
The WGSN approved the name "Schedar" for this star on 21 August 2016 and it is now so included in the List of IAU-approved Star Names. Al-Sufi and Ulug Beg named the star "Al Dhāt al Kursiyy" (Arabic ذات الكرسي, meaning "the lady in the chair"), which Giovanni Battista Riccioli changed to "Dath Elkarti".
Alpha Cassiopeiae | Nomenclature
The current naming system is: The second letter is never nearer the beginning of the alphabet than the first, e.g., no star can be BA, CA, CB, DA and so on.
Variable star designation | Naming
In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Elnath" for this star. In Chinese, (), meaning "Five Chariots", refers to an asterism consisting of β Tauri, ι Aurigae, Capella, β Aurigae and θ Aurigae. Consequently, the Chinese name for β Tauri itself is (; .)
Beta Tauri | Nomenclature
"α Cassiopeiae" (Latinised to "Alpha Cassiopeiae") is the star's Bayer designation. It bore the traditional name "Schedar", which was first encountered in the Alfonsine tables of the thirteenth century. It derives from the Arabic word صدر "şadr", meaning "breast", a word which is derived from its relative position in the heart of the mythological queen Cassiopeia. Johannes Hevelius used the name "Schedir" in his writings, although there were additional traditional spellings of this Arabic transliteration such as "Shedar", "Shadar", "Sheder", "Seder", "Shedis", and "Shedir". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars.
Alpha Cassiopeiae | Nomenclature
German cartographer Johann Bayer used the Greek letters alpha through nu to label the most prominent stars in the constellation. English astronomer John Flamsteed observed and labelled two stars each as delta, epsilon, zeta and nu. He added pi and rho, not using xi and omicron as Bayer used these letters to denote Cygnus and Hercules on his map. The brightest star in the constellation is Vega (Alpha Lyrae), a main-sequence star of spectral type A0Va. Only 7.7 parsecs distant, Vega is a Delta Scuti variable, varying between magnitudes −0.02 and 0.07 over 0.2 days. On average, it is the second-brightest star of a northern hemisphere (after Arcturus) and the fifth-brightest star in all, surpassed only by Arcturus, Alpha Centauri, Canopus, and Sirius.
Lyra | Stars
Alpha Cephei (α Cephei, abbreviated Alpha Cep, α Cep), officially named Alderamin , is a second magnitude star in the constellation of Cepheus near the northern pole. The star is relatively close to Earth at 49 light years ("ly").
Alpha Cephei | Introduction
β Aquarii appears to be a single star to the naked eye, but when viewed with a telescope is seen to have two faint optical companions. The first has an apparent magnitude of 11.0. In 1947, the position angle was observed at 321 degrees with a separation from the Beta Aquarii of 35.4 arcseconds. The second star has a magnitude of 11.6. Its position angle is 186 degrees with a separation from Beta Aquarii of 57.2 arcseconds. As of 2008, there is no definitive evidence that the three stars form a ternary star system, and Gaia Data Release 2 shows the two companions to be around twice the distance of β Aquarii.
Beta Aquarii | Double star
According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Al Naʽām al Ṣādirah" or "Namalsadirah" was originally the title for four stars: φ Sgr as "Namalsadirah I", τ Sgr as "Namalsadirah II", χ Sgr as "Namalsadirah III" and χ Sgr as "Namalsadirah IV" (except σ Sgr and ζ Sgr) .
Phi Sagittarii | Name and etymology
Beta Centauri (Latinised from β Centauri, abbreviated Beta Cen, β Cen), officially called Hadar , is a triple star system in the southern constellation of Centaurus. The system's combined apparent visual magnitude of 0.61 makes it the second-brightest object in Centaurus and one of the brightest stars in the night sky. According to parallax measurements from the astrometric Hipparcos satellite, the distance to this system is about .
Beta Centauri | Introduction
Beta Arietis (β Arietis, abbreviated Beta Ari, β Ari), officially named Sheratan , is a star system and the second-brightest star in the constellation of Aries, marking the ram's second horn.
Beta Arietis | Introduction
Beta Aquarii (β Aquarii, abbreviated Beta Aqr, β Aqr) is a star in the constellation of Aquarius. Based upon parallax measurements obtained during the Hipparcos mission, it is approximately 540 light-years (165 parsecs) from the Sun. The primary or 'A' component is officially named Sadalsuud , the traditional name for the system.
Beta Aquarii | Introduction
This star, along with the other "Aselli" (θ Boo and κ Boo) and λ Boo, were "Aulād al Dhiʼbah" (أولاد الضّباع - "aulād al dhiʼb"), "the Whelps of the Hyenas". In Chinese, (), meaning "Celestial Spear", refers to an asterism consisting of ι Boötis, κ Boötis and θ Boötis. Consequently,the Chinese name for ι Boötis itself is (, .)
Iota Boötis | Nomenclature
Two systems introduced in historical catalogues remain in use to the present day. The first system comes from the German astronomer Johann Bayer's "Uranometria", published in 1603 and regarding bright stars. These are given a Greek letter followed by the genitive case of the constellation in which they are located; examples are Alpha Centauri or Gamma Cygni. The major problem with Bayer's naming system was the number of letters in the Greek alphabet (24). It was easy to run out of letters before running out of stars needing names, particularly for large constellations such as Argo Navis. Bayer extended his lists up to 67 stars by using lower-case Roman letters ("a" through "z") then upper-case ones ("A" through "Q").
Star catalogue | Bayer and Flamsteed catalogues
"β² Sagittarii" (Latinised to "Beta² Sagittarii") is the system's Bayer designation. The designations of the two components as "Beta² Sagittarii A" and "B" derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name "Arkab Posterior" for Beta² Sagittarii on 5 October 2016 and it is now so included in the List of IAU-approved Star Names. For such names relating to members of multiple star systems, and where a component letter (from e.g.
Beta2 Sagittarii | Nomenclature
Lambda Aquarii (λ Aqr, λ Aquarii), informally known as Hydor , is the Bayer designation for a star in the equatorial constellation of Aquarius. The apparent visual magnitude of this star is 3.722, which is bright enough to be visible with the naked eye. It is roughly from Earth.
Lambda Aquarii | Introduction
This system appears among bright stars in a compact pentagon, resembling a quadrilateral due to the suggestive proximity (close arc distance) to Epsilon Hydrae (ε Hya). This shape in the Greco-Roman tradition, which draws on trading and navigation histories shared with nearby older-recorded astrologies is an asterism that represents the head of the water snake. This light source, along with comparable strength (apparent magnitude) Epsilon, δ Hya (Lisan al Sudja), ζ Hya, η Hya, and σ Hya (Minchir), were Ulug Beg's "Min al Azʽal", "Belonging to the Uninhabited Spot". According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Min al Azʽal" or "Minazal" were the title for five stars: δ Hya as "Minazal I", η Hya as "Minazal II", ε Hya as "Minazal III", ρ Hya as "Minazal IV" and ζ Hya as "Minazal V" (exclude σ Hya).
Rho Hydrae | Name and etymology
The Bayer designation Tau Hydrae (τ Hya, τ Hydrae) is shared by two star systems in the equatorial constellation of Hydra. The two stars are separated by 1.74° in the sky. The stars τ Hya and τ Hya, along with ι Hya and the 5th‑magnitude 33 Hya (A Hydrae), were Ptolemy's Καμπή (Kampē); but Kazwini knew them as ʽUḳdah, the Knot. According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Uḳdah" were the title for four stars: τ Hya as "Uḳdah I", τ Hya as "Uḳdah II", 33 Hya as "Uḳdah III" and ι Hya as "Uḳdah IV" In Chinese, (), meaning "Star (asterism)", refers to an asterism consisting of τ and τ Hydrae, Alphard, ι Hydrae, 26 Hydrae, 27 Hydrae, HD 82477 and HD 82428.
Tau Hydrae | Introduction
In the catalogue of stars in the "Calendarium of Al Achsasi Al Mouakket", this star was designated "Lisan al Shudja", which was translated into Latin as "Lingua Hydri", meaning "the snake's tongue". This star, along with ε Hya, ζ Hya, η Hya, ρ Hya and σ Hya (Minchir), were Ulugh Beg's "Min al Azʽal", "Belonging to the Uninhabited Spot". According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Min al Azʽal" or "Minazal" were the title for five stars :δ Hya as "Minazal I", η Hya as "Minazal II", ε Hya as "Minazal III", ρ Hya as "Minazal IV" and ζ Hya as "Minazal V" (exclude σ Hya) In Chinese, (), meaning "Willow (asterism)", refers to an asterism consisting of δ Hydrae, σ Hydrae, η Hydrae, ρ Hydrae, ε Hydrae, ζ Hydrae, ω Hydrae and θ Hydrae Consequently, δ Hydrae itself is known as (, .)
Delta Hydrae | Name and etymology
This is giving the star an oblate shape with an equatorial bulge that is 7% larger than the polar radius. The star has 2.25 times the mass of the Sun and 2.3 times the Sun's radius. It is radiating 39.5 times the Sun's luminosity from its photosphere at an effective temperature of around 9.880. Delta Hydri has been checked for an infrared excess, but none was found.
Delta Hydri | Introduction
Consequently, the Chinese name for δ Tauri itself is (), "the Second Star of Net". The magnitude 4.35 primary, component A, appears to be an A-type subgiant star with a stellar classification of A2 IV. It is a candidate blue straggler and shows characteristics of an Am star. Abt (1985) gave it a classification of A2kA3hA5m, indicating that the spectrum displays the calcium K-line of an A2 star, the hydrogen lines of an A3 star and the metal lines of an A5 star. It is deficient in scandium but has enhanced iron peak and heavy elements. Although suspect of variability in the past, Delta Tauri A was subsequently determined to be photometrically constant.
Delta3 Tauri | Introduction
α Capricorni is a multiple star. The primary (α Cap), 109 light-years from Earth, is a yellow-hued giant star of magnitude 3.6; the secondary (α Cap), 690 light-years from Earth, is a yellow-hued supergiant star of magnitude 4.3. The two stars are distinguishable by the naked eye, and both are themselves multiple stars. α Capricorni is accompanied by a star of magnitude 9.2; α Capricornus is accompanied by a star of magnitude 11.0; this faint star is itself a binary star with two components of magnitude 11. Also called Algedi or Giedi, the traditional names of α Capricorni come from the Arabic word for "the kid", which references the constellation's mythology.
Capricornus | Stars
"β Leonis" (Latinised to "Beta Leonis") is the star's Bayer designation. In Johann Bayer's "Uranometria" (1603), it was designated β (Beta) as the second-brightest star in the constellation. It also bears the Flamsteed designation of "94 Leonis" (assigned on the basis of increasing right ascension rather than luminosity) and additional designations followed as the star was recorded in subsequent star catalogues. The traditional name "Denebola" is shortened from ', from the Arabic phrase ' "" 'tail of the lion', as it represents the lion's tail, the star's position in the Leo constellation. (Deneb in Cygnus has a similar name origin.) In the "Alphonsine Tables" it was recorded as Denebalezeth.
Denebola | Nomenclature
According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", this star was titled as Al Kiladah. This star, together with τ Sgr, ν Sgr, ω Sgr, 60 Sgr and ζ Sgr were "Al Udḥiyy", the Ostrich's Nest.
Psi Sagittarii | Name and etymology
It approved the name "Secunda Hyadum" for the component Delta¹ Tauri Aa on 5 September 2017 and it is now so included in the List of IAU-approved Star Names. In Chinese, (), meaning "Net", refers to an asterism consisting of δ¹ Tauri, Epsilon Tauri, Delta³ Tauri, Gamma Tauri, Alpha Tauri (Aldebaran), 71 Tauri and Lambda Tauri. Consequently, the Chinese name for Delta¹ Tauri itself is (), "the Third Star of Net".
Delta1 Tauri | Nomenclature
"β Herculis" (Latinised to "Beta Herculis") is the star's Bayer designation. It bore the traditional names "Kornephoros", a Greek word meaning "club bearer", and "Rutilicus", a corruption of the Latin word "titillicus", meaning "armpit". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name "Kornephoros" for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names. It was a member of the indigenous Arabic asterism "al-Nasaq al-Shāmī", "the Northern Line" of "al-Nasaqān" "the Two Lines", along with Gamma Herculis, Gamma Serpentis and Beta Serpentis.
Beta Herculis | Nomenclature
This star was one of the set assigned by the 16th century astronomer Al Tizini to Al Sharāsīf (ألشراسيف), the Ribs (of Hydra), which included the stars from β Crateris westward through κ Hydrae. According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Al Sharāsīf" were the title for two stars : β Crateris as "Al Sharasīf II" and κ Hydrae as "Al Sharasīf I". In Chinese, (), meaning "Wings (asterism)", refers to an asterism consisting of β Crateris, α Crateris, γ Crateris, ζ Crateris, λ Crateris, ν Hydrae, η Crateris, δ Crateris, ι Crateris, κ Crateris, ε Crateris, HD 95808, HD 93833, θ Crateris, HD 102574, HD 100219, HD 99922, HD 100307, HD 96819, χ Hydrae, HD 102620 and HD 103462.
Beta Crateris | Name
"Alpha Columbae" is the star's Bayer designation. The traditional name of "Phact" (also rendered "Phad", "Phaet", "Phakt") derives from the Arabic فاجتة "fākhitah" 'ring dove'. It was originally applied to the constellation Cygnus and later transferred to this star. The etymology of its name "hadāri" (unknown meaning) has also been suggested. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Phact" for this star.
Alpha Columbae | Nomenclature
One other first magnitude star Beta Centauri is in the constellation in a position beyond Proxima and toward the narrow axis of Crux, thus with Alpha forming a far-south limb of the constellation. Also called Hadar and Agena, it is a double star; the primary is a blue-hued giant star of magnitude 0.6, 525 light-years from Earth. The secondary is of magnitude 4.0 and has a modest separation, appearing only under intense magnification due to its distance. The northerly star Theta Centauri, officially named Menkent, is an orange giant star of magnitude 2.06. It is the only bright star of Centaurus that is easily visible from mid-northern latitudes.
Centaurus | Stars
With π, σ, σ, ρ, A and d, it composed the Arabic asterism "Al Ṭhibā᾽", the Gazelle. According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Al Ṭhibā" were the title for seven stars : A as "Althiba I", this star (π) as "Althiba II", π as "Althiba III", ρ as "Althiba IV", σ as "Althiba V", σ as "Althiba VI", and d as "Althiba VII".
Pi1 Ursae Majoris | Naming and etymology
The asteroids , and were also named after the mythological Seven Sisters. In 1861, the director of the discovering observatory, George Phillips Bond, raised a minor concern since these names had already been applied to some of the brightest stars of the Pleiades in the constellation of Taurus: Maia, Electra, Asterope and Merope.
66 Maja | Double naming
γ Hydri, Latinised as Gamma Hydri, is a solitary, red-hued star in the constellation Hydrus. It has an apparent visual magnitude of 3.26, making it easily visible to the naked eye at night. Based upon an annual parallax shift of 15.24 mas as measured from Earth, the system is located about 214 light years from the Sun. This is an evolved red giant star with a stellar classification of M1 III, and is most like on the asymptotic giant branch of the HR diagram. It is a semiregular variable that pulsates between magnitudes 3.26 and 3.33, although its period is not known precisely.
Gamma Hydri | Introduction
"α Andromedae" (Latinised to "Alpha Andromedae") is the star's Bayer designation. Ptolemy considered Alpha Andromedae to be shared by Pegasus, and Johann Bayer assigned it a designation in both constellations: Alpha Andromedae (α And) and Delta Pegasi (δ Peg). When the modern constellation boundaries were fixed in 1930, the latter designation dropped from use. The star bore the traditional names "Alpheratz" () or "Alpherat" and "Sirrah" deriving from the Arabic name, سرة الفرس "the navel of the mare". (سرة alone is ). The word "horse" reflects the star's historical placement in Pegasus. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars.
Alpha Andromedae | Nomenclature
In combination with Beta Trianguli, these stars were called "Al Mīzān", which is Arabic for "The Scale Beam".
Alpha Trianguli | Nomenclature
In Chinese, (), meaning "Celestial Drumstick", refers to an asterism consisting of θ Aquilae, 62 Aquilae, 58 Aquilae and η Aquilae. Consequently, the Chinese name for θ Aquilae itself is (, .) In the catalogue of stars in the "Calendarium" of Al Achsasi al Mouakket, this star was designated "Thanih Ras al Akab" (تاني ألرأس ألعقاب - "taanii al ra’s alʕuqāb"), which was translated into Latin as "Secunda Capitis Vulturis", meaning "the second (star) of eagle's head". This star, along with δ Aql and η Aql, were "Al Mizān" (ألميزان), the Scale-beam. According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Al Mizān" were the title for three stars :δ Aql as "Al Mizān I", η Aql as "Al Mizān II" and θ Aql as "Al Mizān III".
Theta Aquilae | Etymology
"α Cygni" (Latinised to "Alpha Cygni") is the star's designation given by Johann Bayer in 1603. The traditional name "Deneb" is derived from the Arabic word for "tail", from the phrase ذنب الدجاجة "Dhanab al-Dajājah", or "tail of the hen". The IAU Working Group on Star Names has recognised the name "Deneb" for this star, and it is entered in their Catalog of Star Names. "Denebadigege" was used in the "Alfonsine Tables", other variants include "Deneb Adige", "Denebedigege" and "Arided". This latter name was derived from "Al Ridhādh", a name for the constellation. Johann Bayer called it "Arrioph", derived from "Aridf" and "Al Ridf", 'the hindmost' or "Gallina".
Deneb | Nomenclature
The designation "b" derive from the order of discovery. The designation of "b" is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet. In the case of HD 164922, only one was discovered, which was designated "b", then a more inner planet, which was designated "c". The name HD 164922 derives directly from the fact that the star is the 164,922nd star discovered in the Henry Draper catalog.
HD 164922 | Nomenclature