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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Number of Results: 3079 Search : on
Orion Nebula
  میغِ شکارگر، ~ ِ ا ُریون   
miq-e Šekârgar, ~ Oryon

Fr.: Nébuleuse d'Orion   

The best known → ionized nebula and one of the nearest regions to the Sun in which stars are presently being formed. It is visible to the naked eye in the constellation → Orion south of → Orion's Belt as a fuzzy patch. It lies about 1,500 → light-years away and measures about 30 light-years across. The Orion Nebula is ionized and made visible by a small group of → O-type and → B-type stars known as the → Trapezium cluster. Other designations: M 42, NGC 1976. See also: → Orion molecular cloud; → Huygens Region ; → Orion association; → Orion Bar; → Orion Bright Bar.

Orion; → nebula.

Orion OB1 Association
  آهزش ِ OB1 شکارگر، ~ ~ اریون   
âhazeš-e OB1 Šekârgar, ~ ~ Oryon

Fr.: Association Orion OB1   

An → OB association consisting of several dozen → hot stars of → spectral types O and B (→ O star, → B star). The Orion OB1 association consists of several subgroups, first divided by Blaauw (1964) into four subgroups. The subgroups differ in age and gas and dust content:
Orin OB1a, which contains the stars to the northwest of → Orion's Belt stars. Within this group lies another subgroup, known as the → 25 Orionis group;
Orion OB1b, containing the group of stars located in and around the Belt;
Orion OB1c, including the stars around → Orion's Sword; and
Orion OB1d, which contains the stars in and close to the → Orion Nebula (including the → Trapezium cluster).

Orion; → OB association.

Orion Spur
  شخاک ِ شکارگر   
šaxâk-e šekârgar

Fr.: éperon d'Orion   

Same as → Orion Arm.

Orion; → → spur.

Orion's Belt
  کمربندِ شکارگر، ~ اُریون   
kamarband-e Šekârgar, ~ Orion

Fr.: Ceinture d'Orion   

Three prominent stars in the central regions of the constellation → Orion that align to form the "belt" of the mythological Hunter. They are → Alnitak (ζ Ori), → Alnilam (ε Ori), and → Mintaka (δ Ori). The easternmost star Alnitak is separated from the middle one, Alnilam, by 1°.36, and the westernmost Mintaka has an angular distance of 1°.23 from Alnilam. Their distance is between 800 and 1,300 → light-years from Earth. They probably formed inside the same → molecular cloud less than 10 million years ago.

Orion; → belt.

Orion's Sword
  شمشیر ِ شکارگر، ~ اریون   
Šamšir-e Šekârgar, ~ Oryon

Fr.: Epée d'Orion   

An astronomical → asterism in the constellation → Orion forming an almost vertical line beneath → Orion's Belt. From north to south, the most prominent objects in the Sword are the cluster NGC 1981, the star → 42 Orionis, the famous → Orion Nebula, and the Sword's brightest star → Iota Orionis (→ Hatsya). None of these objects is particularly bright in itself, but their proximity to one another and the nebulosity across much of this region makes the Sword stand out clearly in the night sky.

Orion; → sword.

Orion-Cygnus Arm
  بازوی ِ شکارگر-ماکیان   
bâzu-ye šekârgar-mâkiyân

Fr.: bras Orion-Cygne   

Same as → Orion Arm.

Orion; → Cygnus; → arm.

Orionids
  شکارگریان   
Šekârgariyân

Fr.: orionides   

A meteor shower that appears to emanate from the constellation → Orion. It peaks between October 14 and 20 with about 20 meteors per hour.

Orion + → -ides.

orthogonal
  ارداکنج   
ardâkonj

Fr.: orthogonal   

In elementary geometry, pertaining to or involving right angles or perpendiculars.
Of a system of real functions, defined so that the integral of the product of any two different functions is zero.
Of a linear transformation, defined so that the length of a vector under the transformation equals the length of the original vector.
Of a square matrix, defined so that its product with its transpose results in the identity matrix.

ortho- + gonia "angle," related to gony "knee;" L. genu "knee;" Mod.Pers. zânu "knee;" Av. žnav-, žnu- "knee;" Skt. janu-; PIE base *g(e)neu-, see below, + → -al

Ardâkonj, from ardâ-, → ortho-, + konj "angle, corner, confined place" (variants xong "corner, angle," Tabari kânj, Kurd. kunj, Hamadâni kom), maybe from the PIE base *g(e)neu-, as above, and related to Mod.Pers. zânu "knee" (Av. žnu-), Skt. kona- "angle, corner," Gk. gony, gonia, L. cuneus "a wedge," Albanian (Gheg dialect) kân "angle, corner," Albanian (Toks) kënd "angle, corner."

orthogonal functions
  کریاهایِ ارداکنج   
karyâhâ-ye ardâkonj

Fr.: fonctions orthogonales   

A set of functions, any two of which, by analogy to orthogonal vectors, vanish if their product is summed by integration over a specified interval.

orthogonal; → function.

orthogonal lines
  خط‌هایِ ارداکنج   
xatthâ-ye ardâkonj

Fr.: droites orthogonales   

Perpendicular lines.

orthogonal; → line.

orthogonal trajectory
  ترایشانه‌ی ِ ارداکنج   
tarâyešâne-ye ardâkonj

Fr.: trajectoire orthogonale   

Math.: An → isogonal trajectory where the family of curves are cut at right angles.

orthogonal; → trajectory.

orthogonal vectors
  بردارهای ِ ارداکنج   
bordârhâ-ye ardâkonj

Fr.: vecteurs orthogonaux   

Two non-zero vectors which are perpendicular, i.e. their → scalar product is zero.

orthogonal; → vector.

orthogonality
  ارداکنجی   
ardâkonji

Fr.: orthogonalité   

1) The property of → orthogonal functions.
2) The following conditions satisfied by the → Fourier series:
∫ cos (mx) sin (nx) dx = 0 (summed from -π to +π) for all m, n
∫ cos (mx) cos (nx) dx = 0 (summed from -π to +π) for all m ≠ n, = 2π for m = n = 0, = π for (m = n) > 0
∫ sin (mx) sin (nx) dx = 0 (summed from -π to +π) for m ≠ n, = π for (m = n) > 0.

orthogonal; → -ity.

orthonormal vectors
  بردارهای ِ ارداهنجارور   
bordârhâ-ye ardâhanjârvar

Fr.: vecteurs orthonormaux   

Two non-zero vectors that are → orthogonal and have magnitude 1.

orthogonal; → vector.

oscillation
  نَوِش   
naveš (#)

Fr.: oscillation   

The state of any quantity when the value of that quantity is continually changing so that it passes through maximum and minimum values.

Verbal noun of → oscillate.

oscillation mode
  ترز ِ نَوِش، مُد ِ ~   
tarz-e naveš, mod-e ~

Fr.: modes d'oscillation   

Same as → pulsation mode.

oscillation; → mode.

osculation
  آبوسش   
âbuseš

Fr.: osculation   

The contact between two osculating curves or the like.

Verbal noun of → osculate

Ostriker-Peebles criterion
  سنجیدار ِ استرایکر-پیبلس   
sanjidâr-e Ostriker-Peebles

Fr.: critère d'Ostriker-Peebles   

An approximate empirical criterion for the stability of a → galactic disk against its collapse to form a bar. The disk is stable if the following relation holds: T/|W| < 0.14, where T is the rotational → kinetic energy and |W| is the absolute value of the gravitational → potential energy. While the → Toomre criterion applies only to small linear perturbations, the Ostriker-Peebles criterion describes global modes.

Ostriker & Peebles, 1973, ApJ 186, 467; → criterion.

outer Lindblad resonance (OLP)
  باز‌آوایی ِ لیندبلاد ِ برونی   
bâzâvâyi-ye Lindblad-e boruni

Fr.: résonance de Lindblad externe   

A → Lindblad resonance expressed by: Ωp = Ω + κ/m.

outer; → Lindblad resonance.

overtone
  اَبَرتن   
abarton (#)

Fr.: harmonique   

A note of lesser intensity and higher frequency than the fundamental note, and superimposed upon the latter to give a note of characteristic quality. Overtones whose frequencies are an integral multiple of the fundamental are said to form a harmonic series. The fundamental with a frequency f1 is the first harmonic. The frequency 2f1 is the first overtone and so on.

over-; → tone.

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