An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

→ alpha process.

→ alpha; → ladder.

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

→ alpha; → offset.

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.

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.

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 dwarf→ companion. 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".

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".

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".

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."

The brightest star in → Aquila (apparent visual magnitude 0.77), and the twelfth brightest star in the sky. Altair is a whitish A7 → main sequence star. It has one of the fastest known rotational speeds, 242 km/s at the equator, compared with the Sun's about 2 km/s.

Altair, from Ar. An Nasr at-Taiir "The Flying Vulture," from Nasr "vulture" + Ta'ir "flying."

Karkas-e Parandé "The Flying Vulture" coined by Biruni (around A.D. 1000), from karkas "vulture," Av. kahrkâsa- "devourer hen," from *kahrka "hen" (Mod.Pers. kark "hen," karak "quail") + *âsa "to eat" (Mod.Pers. âš "food, soup") + Parandé "flying," from paridan "to fly" (from Mid./Mod.Pers. par(r) "feather, wing," Av. parəna- "feather, wing;" cp. Skt. parna "feather," E. fern; PIE *porno- "feather").

1) A → mounting for → telescopes that permits both → vertical and → horizontal → rotation.
2) A telescope having such a mounting.
See also: → altazimuth coordinate system, → altazimuth instrument, → altazimuth mounting.

Altazimuth, from alt(itude) + → azimuth.

Farâzâ-sugân, from farâzâ, → altitude, + sugân, → azimuth.

The coordinate system in which the position of a body on the → celestial sphere is described with respect to an observer's → celestial horizon and → zenith. The coordinates of a point in this system are its → altitude on the → vertical circle, and its → azimuth westward (clockwise) along the celestial horizon from the observer's south. Same as → horizon coordinate system.

→ altazimuth; → coordinate; → system.

A telescope that moves vertically along the → altitude circle of a celestial body and horizontally along its → azimuth circle.

→ altazimuth; → instrument.

A → telescope mounting which has its two axes of movement aligned with the → horizon and the → zenith.

→ mounting; → mounting.

(v.tr.) To change or make different.
(v.intr.) To change or become different.

M.E. alteren, from O.Fr. altérer, from M.L. alterre, from L. alter "other," from PIE *al- "beyond" + comp. suffix -ter.

Degargun kardan, degargunidan, from degargun, from degar, → change, + -gun "manner, fashion," → elliptical, + kardan, -idan, → -ize.

1) The act or process of altering; the state of being altered.
2) The result of altering.

Verbal noun of → alter.

1) Happening or following in turns; succeeding each other continuously.
2a) (v.intr.) To occur in a successive manner (day alternates with night); To change back and forth from one state, action, or place to another.
2b) Electricity: To reverse direction at regular intervals in a → circuit.
3) (v.tr.) To do or execute in succession or one after another (to alternate work and rest).

From L. alternus "one after the other," p.p. of alternare "to do first one thing, then the other," from alternus "every other," from alter "the other".

1) Peyvâr from pey "step; after" (as in peyâpey "successively, repeatedly") + Pers. vâr "turn (succession), time (repetition), alternation". Compare with Skt. vâra "one's turn, appointed time, alteration, succession".
2, 3) Peyvâr šodan, peyvâr kardan, peyvâridan, verbs from peyvâr "alternate," as above.

Occuring in a successive manner. Acting or proceeding by turns. → alternating current.

Verbal adj. from → alternate; → -ing.

An → electric current that reverses direction of flow at regular intervals. The typical alternating current is → sinusoidal in shape. Alternating current has the advantage over → direct current in that its → voltage magnitude can be changed easily through a → transformer. Moreover, it is safer to transfer over the longer city distances and can provide more → power. The frequency of alternating current is 50 Hz (Europe) or 60 Hz (USA).

→ alternating; → current.

General: Successive change from one thing or state to another and back again.
The process of periodically varying a voltage from zero to a maximum, back to zero, to a minimum, and then to zero.

Alternation, noun from → alternate.

1) (n) A proposition or situation offering a choice between two or more things only one of which may be chosen.
2) (adj) Offering or expressing a choice. → alternative energy, → alternatively.

Alternative, from → alternate.

Degarine, from degar "other," variant digar, from Mid.Pers. dit, ditikar "the other, the second," O.Pers. duvitiya- "second," Av. daibitya-, bitya- "second," Skt. dvitiya- "second," PIE *duitiio- "second" + suffix -ine.