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

A system in which the → damping is great enough to prevent oscillation.

Aperiodic, from → a- + periodic; + → damping.

Same as → bijection.

→ bijective; → mapping.

Of a → molecular cloud, the property of being made up of → clumps.
The extent with which a molecular cloud is → clumpy.

Clumpiness, from → clumpy + → -ness.

Gudegi from gudé, → clump, + -gi suffix forming noun from adjectives ending in -é.

The massing together of material to form clumps. → wind clumping.

→ clump; → -ing.

The ratio f_cl = <ρ²> / <ρ >², where ρ represents the → stellar wind density and the brackets mean values. Unclumped wind has f_cl = 1 and → clumping becomes significant for f_cl≅ 4.

→ clumping; → factor.

Same as the → Landau damping.

→ collision; → -less; → damping.

A continuous mapping u = f(x) of a domain D in an n-dimensional Euclidean space (n≥ 2) into the n-dimensional Euclidean space is called conformal at a point x₀∈ D if it has the properties of constancy of dilation and preservation of angles at this point.

→ conformal; → mapping.

Of an oscillating system, the progressive decrease with time in the amplitude of the oscillation, due to friction (internal or external) or other resistance.

M.E. damp "black damp, a poison gas occurring in a mine," from Mid.Du. or Mid. Low German; akin to O.H.G. damph "vapor."

Mirâyi, noun from mirâ "getting extinguished, going out, expiring, dying," from mordan, present tense stem mir- "to die," Mid.Pers. murdan "to die," O.Pers. mrt- "to die," amriyta "dies," martiya- "(mortal) man" (Mod.Pers. mard "man"), Av. mərəta- "died," Skt. mar- "to die," mrti- "death;" PIE base *mor-/*mr- "to die." Cognates in other IE languages: Gk. emorten "died," ambrotos "immortal," L. morior "I die," mortuus "dead" (Fr. mourir "to die," mort "dead"), Arm. merani- "to die," O.C.S. mrutvu "dead," O.Ir. marb, Welsh marw "died," O.E. morþ "murder," Lith. mirtis "man."

The addition of minute quantities of impurities to a semiconductor to achieve a desired characteristic.

Verbal noun of → dope.

The monitoring and/or examining the data that is passed over the network without sender and receiver's permission and/or knowledge. For example, a user on the Internet could eavesdrop on someone's phone conversation or e-mail.

Noun from → eavesdrop.

A method for imaging the continuum light distributions of the → accretion disks of → cataclysmic variable stars. It relies on geometrical information contained in eclipse light curves. An alternative method is → Doppler tomography.

→ eclipse; → mapping.

A theoretical limit of approximately 6 × 10¹⁹  → electron-volts for the energy of → cosmic rays above which they would lose energy in their interaction with the → cosmic microwave radiation background photons. Cosmic ray protons with these energies produce → pions on blackbody photons via the Δ resonance according to: γ_CMB + p → p + π⁰, or γ_CMB + p → n + π⁺, thereby losing a large fraction of their energy. These interactions would reduce the energy of the cosmic rays to below the GZK limit. Due to this phenomenon, → Ultra-high-energy cosmic rays are absorbed within about 50 Mpc.

Named after Kenneth Greisen (1966), Physical Review Letters 16, 748 and Georgiy Zatsepin & Vadim Kuzmin (1966), Journal of Experimental and Theoretical Physics Letters 4, 78; → limit.

The act or process of uniting into groups.
A collection of things assembled into a group.
The occurence of several astronomical objects, usually of the same category, in a region of the sky.

Verbal noun of → group.

Same as → isospin.

Isobaric, adj. of → isobar; → spin.

A quantum number based on the assumption that the nucleon (proton and neutron) is a single entity having two states, like → spin. It is conserved by the strong interaction. Same as isotopic spin, isobaric spin.

From → iso- + → spin

Same as → isospin.

→ isotopic; → spin.

The process wherein a → plasma gains energy at the expense of the → Langmuir wave. In the presence of the → Landau resonance, the particles in resonance moving slightly faster than the wave lose energy, while those moving slightly slower will gain energy. Since the Maxwellian distribution is decreasing with velocity, in a Maxwellian plasma, near the Landau resonance, there are more particles at lower velocities than at higher velocities. Also called collisionless damping.

Lev Landau (1908-1968), a prominent Soviet physicist, 1962 Nobel Prize in Physics for his development of a mathematical theory of → superfluidity; → damping.

1) The process of producing a map.
2) Math.: The operation of establishing → relations between two → sets in which one element of the second set is assigned to each element of the first set, as the expression y = x². Same as → function.

Verbal noun from → map + → -ing.

1) Naqšé bardâri;, → map.
2) Hamtâyeš, verbal noun of hamtâyidan literally "folding together, relating units together," from ham- "together," → com-, + tâ "fold, plait, ply; piece, part; single, a single unit of a pair," also a multiplicative suffix; Mid.Pers. tâg "piece, part," + infinitive suffix -idan.

The total → angular momentum of a → nucleus, represented by symbol I. The nucleus, which is composed of neutrons and protons, acts as if it is a single entity which has intrinsic angular momentum. The nuclear spin depends on the → mass number; if the mass number is odd then the nucleus has half-integer spin like the electron while if the nucleus has even mass number then its spin will be integer spin.

→ nuclear; → spin.

To hold or express an opinion.

Verb for → opinion.