An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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alpha
  آلفا   
âlfâ (#)

Fr.: alpha   

The first letter of the Greek alphabet (A, α).

Gk. alpha, from Hebrew or Phoenician → aleph.

Alpha Capricornids
  وهیگیان   
Vahigiyân

Fr.: Capricornides   

An annual → meteor shower that takes place within the boundaries constellation → Capricornus near the star named Alpha. The meteor shower is visible between July 03 and August 15 with the peak occurring on July 30. Alpha Capricornids meteors are bright and often include spectacular colorful → fireballs.

alpha; → Capricornus.

Alpha Centauri
  آلفا-کنتا‌ؤرس   
Âlfâ-Kentawros

Fr.: Alpha du Centaure   

Brightest star in the constellation → Centaurus (V = -0.01 magnitude) and third brightest star in the sky; also known as → Rigil Kent. It is a main-sequence star of the same spectral class (G2 V) as the Sun. Actually, Alpha Centauri is a triple-star system, the components being designated A, B, and C. The component C is also called → Proxima Centauri because it is the closest star to the Earth (other than the Sun), at a distance of 4.22 → light-years, but it is too dim to be seen with the naked eye. Components A and B are currently about 4.36 light-years away.

Alpha (α), a Gk. letter of alphabet used in the → Bayer designation; Centauri, genitive of → Centaurus.

Alpha Centauri system
  راژمان ِ آلفا-کنتا‌ؤرس   
râžmân-e Âlfâ-Kentâwros

Fr.: système Alpha du Centaure   

A system of three stars, the → close binary Alpha Centauri A (→ spectral type G2 V) and Alpha Centauri B (K1 V), and a small and faint → red dwarf, Alpha Centauri C (M6 Ve), better known as → Proxima Centauri. To the unaided eye, the two main components (AB) appear as a single object with an → apparent visual magnitude of -0.27, forming the brightest star in the southern constellation → Centaurus and the third brightest star in the night sky, after → Sirius and → Canopus. The individual visual magnitudes of the components A, B, and Proxima are +0.01, +1.33, and +11.05, respectively. The masses of A and B are 1.100 and 0.907 Msun, respectively. Their → effective temperatures are (A) 5,790 K and (B) 5,260 K; their luminosities (A) 1.519 Lsun and (B) 0.500 Lsun. The binary members are separated in average by only 23 → astronomical units. They revolve around a common center of mass with a period of about 80 years. Both have a distance of 4.37 → light-years. Proxima Centauri, lying about 15,000 AU apart from AB, is → gravitationally bound to them. It has a mass of 0.1 Msun, a radius of 0.1 Rsun, a luminosity of about 0.001 Lsun, and an → effective temperature of ~ 3,000 K.

alpha; → Centaurus; → system.

alpha decay
  تباهی ِ آلفا   
tabâhi-ye Âlfâ

Fr.: désintégration Alpha   

The radioactive transformation of a nuclide by alpha-particle emission. Also called alpha disintegration.

alpha; → decay.

alpha disk model
  مدل ِ گرده آلفا، ~ دیسک ~   
model-e gerdé âlfâ, ~ disk ~

Fr.: modèle disque alpha   

A simple → accretion disk model in which the → angular momentum is transported outward by action of some kind of → viscosity. In this model, first proposed by Shakura & Sunyaev (1973), the turbulent kinematic viscosity is given by ν = α cs H, where α is a parameter, cs the sound speed in the medium, and H → scale height. The α parameter controls the amount of → turbulence in the medium whose H and cs are upper limits for → mixing length and turbulent speed, respectively. Values of α = 10-3 to 10-2 yield evolution → time scales that are broadly consistent with the ages inferred for → T Tauri stars. A weak point of this model is the arbitrariness of the choice of the parameter α, which reflects the lack of a rigorous theory of turbulence.

alpha, the parameter name; → disk; → model.

alpha drive
  رانه‌ی ِ آلفا، ~ راست‌افراز   
râne-ye âlfâ, ~ râstafrâz

Fr.: entraînement en ascension droite   

The → mechanism that imparts or transfers power to a → telescope so that it can move along the → right ascension direction. See also → tacking.

alpha, → right ascension; → drive.

alpha effect
  اسکر ِ آلفا   
oskar-e Alfâ

Fr.: effet α   

In the → solar dynamo model, the process whereby the → azimuthal magnetic field transforms into a → meridional magnetic field due to the interaction of → convection and → differential rotation. See also → omega effect.

alpha; → effect.

alpha element
  بن‌پار ِ آلفا   
bonpâr-e âlfâ

Fr.: élément α   

A → chemical element synthesized in → massive stars by → alpha particle capture leading to iron before the advent of a → type II supernova. Stable alpha elements are: C, O, Ne, Mg, Si, S, Ar, Ca.

alpha; → element.

alpha element knee
  زانوی ِ بن‌پار ِ آلفا   
zânu-ye bonpâr-e âlfâ

Fr.:   

The point in the plot showing → alpha element abundances ([α/Fe]) of a galaxy as a function of the → metallicity ([Fe/H]) where the α-element abundance drops. The metallicity of the turn-over in α-element abundances is linked to the → star formation rate during the early stage of star formation in a galaxy and therefore also depends on the total mass of the system. Higher star formation efficiency leads to higher overall metallicity before the onset of → Type Ia supernova → enrichment, and thus to a knee that is located at higher [Fe/H] values.

alpha; → element; → knee.

alpha emission
  گسیل ِ آلفا   
gosil-e âlfâ

Fr.: émission alpha   

The release of → alpha particles at high velocity from an atom's nucleus as it undergoes radioactive transformation.

alpha; → emission.

alpha emitter
  گسیلنده‌ی ِ آلفا   
gosilandé-ye âlfâ

Fr.: émetteur d'alpha   

An atomic nucleus decaying by an → alpha particle emission.

alpha; → emitter.

alpha ladder
  نردبان ِ آلفا   
nardebân-e âlfâ

Fr.: échelle alpha   

alpha process.

alpha; → ladder.

alpha offset
  اپنه ِ آلفا   
apneh-e Âlfâ

Fr.: offset en ascension droite   

A short distance from the target, in right ascension, where the telescope is pointed for various purposes.

alpha; → offset.

alpha particle
  ذره‌ی ِ آلفا   
zarre-ye Âlfâ

Fr.: particule alpha   

A positively charged particle emitted from the nuclei of certain atoms during radioactive disintegration. The alpha particle has an atomic weight of 4 and a positive charge equal in magnitude to 2 electronic charges; hence it is essentially a helium nucleus.

alpha; → particle.

alpha process
  فراروند ِ آلفا   
farâravand-e âlfâ

Fr.: processus α   

A class of → nuclear fusion reactions by which stars convert → helium into → heavy elements. Once carbon has been created, through → triple alpha process, in a star's interior, it can then continue to fuse with further → alpha particles to produce progressively heavier elements called → alpha particles. The first stage produces oxygen, followed by neon, magnesium, silicon, sulfur, argon, calcium, titanium, chromium and iron. This is known as the → alpha ladder, with energy released as a photon at each stage.

alpha;→ process.

Alphard (α Hydrae)
  الفرد   
Alfard (#)

Fr.: Alphard   

The only bright star in the constellation → Hydra, that has a magnitude of about 2 and a reddish color. Alphard is a giant of spectral type K3, and has a → white dwarfcompanion. Alphard is mild barium star probably contaminated by its companion before becoming a white dwarf.

Alphard, from Ar. Al-Frad ash-Shuja' "the solitary of the Serpent," from Frad "solitary" + Shuja' "a species of serpent".

Alphekka (α Coronae Borealis)
  الفکه   
Alfakké (#)

Fr.: Alphekka   

Also known as Gemma, the brightest star in Corona Borealis (visual magnitude 2.23). Alphekka is an A type dwarf lying at about 7 → light-years. Actually it has a faint Sun-like (G5 V) companion, that produces an eclipse of the primary every 17.4 days.

Alphekka, from Ar. Nayyir al-Fakkah "the bright of the broken" (ring of star), from Nayyir "bright" + fakkah "broken," from fakk "to disjoin, unloose".

Alpheratz (α Andromedae)
  رأس‌المسلسله   
Ra's-ol-Mosalsalé

Fr.: Alphératz   

The brightest star in → Andromeda with a visual magnitude of 2.07. Alpheratz is a blue → subgiant star of spectral type B8 IV lying at a distance of about 97 → light-years. It is particularly remarkable because of the unusual strength of mercury and manganese absorption lines in its spectrum.

Other names for this star are Alpherat, Sirrah, or Sirah. These names derive from Ar. As-Surrat al-Faras (السره‌الفرس) "The Horse's Navel," from surrat (سره) "navel" + faras (فرس) "horse". The name refers to the location of the star in the figure of → Pegasus. However, the star is now considered to belong to the constellation → Andromeda.

Ra's-ol-Mosalsalé, from Ar. Ar-Ra's al-Mar'ah al-Musalsalah "The head of the chained woman," from Ra's "head" + Mar'ah "woman" + Musalsalah "chained".

already
  پیشنون   
pišnun

Fr.: déjà   

1) By this or that time; previously; prior to or at some specified or implied time.
2) Now; so soon; so early (Dictionary.com).

From M.E. al redy, literally "fully ready," → all, + M.E. redy "ready," from rædig, from O.E. ræde "prompt" + -ig "-y."

Pišnun, literally "prior to now," from piš-, → pre-, + Mid./Mod.Pers. nun "now, at present" (variants aknun, konun, ultimately from Proto-Ir. *hak-nun); Av. nū- "now," nūrəm "now;" O.Pers. nūram "now;" cf. Skt. nú- "now, just, but," nūnám "now, at present, indeed;" Gk. nun "now;" L. nu- "now" (in nu-dis "the day after tomorrow"); Goth. nu "now;" O.E. nu; E. now; PIE base *nu- "now."


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<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl ura uti val var vec vel ver Ver vie vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>