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

Of, pertaining to, or occurring at the beginning.

Initial, from L. initialis, from initium "a beginning, an entrance," from p.p. stem of inire "to go into, begin," from → in- + ire "to go," → ion.

Âqâzin "pertaing to the beginning," from âqâz "beginning," from Proto-Iranian *āgāza-, from prefix ā- + *gāz- "to take, receive," cf. Sogdian āγāz "beginning, start," pcγz "reception, taking."

1) Conditions at an initial time t = t₀ from which a physical system or a given set of mathematical equations evolves.
2) Meteo.: A prescription of the state of a → dynamical system at a specified time; for all subsequent times, the → equation of motion and → boundary conditions determine the state of the system.

→ initial; → condition.

The mass of a star at its arrival on the → main sequence.

→ initial; → mass.

A mathematical expression describing the relative number of stars found in different ranges of mass for a cluster of stars at the time of its formation. It is defined as φ(log M) = dN / dlog M ∝ M ^-Γ, where M is the mass of a star and N is the number of stars in a logarithmic mass interval. The value of the slope found by Salpeter (1955) for → low-mass and → intermediate-mass stars in the → solar neighborhood is Γ = 1.35. The IMF can be expressed also in linear mass units: χ(M) = dN / DM ∝ M ^-α. Note that χ(M) = (1 / M lm 10) φ(log M), and α = Γ + 1. In this formalism the Salpeter slope is α = 2.35. There is a third way for representing the IMF, in which the exponent is x = -α. The IMF is not a single power law over all masses, from → brown dwarfs to → very massive stars (Kroupa, 2002, Science 295, 82). Different slopes have been found for different mass segments, as follows: α = 1.3 for 0.08 ≤ M_solar < 0.5; α = 2.3 for 0.5 ≤ M_solar < 1; α = 2.3 for 1 ≤ M_solar. The IMF at low masses can be fitted by a → lognormal distribution (See Bastian et al., 2010, ARAA 48, 339 and references therein). See also → canonical IMF.

→ initial; → mass; → function.

The value of the phase corresponding to the origin of time. Same as the → epoch angle.

→ initial; → phase; → angle.

An instant of infinite density, infinite pressure, and infinite temperature where the equations of general relativity break down, if the standard Big Bang theory is extrapolated all the way back to time zero. → singularity.

→ initial; → singularity.

1) The first step or action of a matter; commencing move.
2) An introductory act or step; leading action.

From Fr. initiative, from L. initiatus, p.p. of initiare "to begin," from initium "a beginning," → initial.

Bongâm, from bon "basis; root; foundation; bottom," → fundamental, + gâm "step, pace," → egress.

1) General: To force into a passage, cavity, or tissue.
2) Math.: Verbal form related to → injection.

From L. injectus, p.p. of injicere "to throw in or on," from → in- "in" + -icere, combining form of jacere "to throw."

Daršândan, from darešândan, from dar-, → in, + ešândan, → eject.

1) General: The act of injecting. Something that is injected.
2) Physics: The process of introducing electrons or holes into a semiconductor so that their total number exceeds the number present at thermal equilibrium. → hole injection.
3) Math.: A one-to-one → mapping. In other words, a mapping from a → set A onto a set B such that for every element in B there is at the most an element in A.

Verbal noun of → inject.

Of or pertaining to a → injection.

Adj. related to → injection.

A small arm of the sea, a lake, or a river.

From → in- + let "to allow," M.E. leten, O.E. lætan; cognate with Du. laten, Ger. lassen, akin to Gk. ledein "to be weary", L. lassus "tired."

Šâxâbé, literally "branch of water," from šâx, → branch, + âb "sea, river, → water" + noun suffix -é.

Situated within or farther within; interior.

From O.E. inra, comparative of inne (adv.) "inside;" → in-.

Daruni, adj. of darun "in, into; within" (Mid.Pers. andarôn "inside," from andar, → inter-, + rôn "side, direction;" Av. ravan- "(course of a) river").

The central part of the → Earth's core, composed of solidified → iron and → nickel, and extending from a depth of about 5100 km to the center of the Earth, at 6360 km. Its radius is about 1/3 that of the whole core and is effectively decoupled from the → mantle due to the molten nature of the surrounding → outer core. The radius of the inner core is defined by a small increase in → compressional wave velocity at a radius of about 1200 km. Its density is about 12 g/cm³. The → temperature of the inner core has been estimated at 5000-7000 °C.

→ inner; → core.

A → near-Earth object whose → orbit lies always inside Earth's orbit.

→ inner; → Earth; → object.

One of the five → Lagrangian points, denoted L1, which lies between the two bodies on the line passing through their center of mass. In a → close binary star system mass transfer occurs through this point.

→ inner; → Lagrangian points.

A → Lindblad resonance expressed by: Ω_p = Ω - κ/m.

→ inner; → Lindblad resonance.

The planets Mercury, Venus, Earth and Mars collectively. T hey are also known as the terrestrial planets.

→ inner; → planet.

The smallest → circular orbit in which a particle can stably orbit a → black hole according to → general relativity without the risk of falling past the → event horizon. In other words, the ISCO is the inner edge of the → accretion disk around a black hole. Therefore, characteristics of accretion disks depend on ISCO. The radius of ISCO is calculated to be three times the → Schwarzschild radius (3 R_Sch). ISCO is closer to event horizon for rotating black hole.

→ inner; → stable; → circular; → orbit.

A dynamical model developed in France since 2003 which calculates the motion of → Solar System bodies with the highest accuracy. It integrates data obtained by NASA and ESA space missions. See, for example, A. Fienga et al. 2011, arXiv:1108.5546.

INPOP, short for Intégration Numérique Planétaire de l'Observatoire de Paris; → ephemerides.

1) The current, voltage, or driving force applied to an electric or electronic circuit or device.
2) Computers: Data which is transferred from outer external storage elements to the internal storage of a computer. → output.

From → in- + put, from M.E. put(t)en "to push, thrust, put;" O.E. *putian.

Darundâd, from darun "in" → in-, → intra-, + dâd "given," p.p. of dâdan "to give" (Mid.Pers. dâdan "to give," O.Pers./Av. dā- "to give, grant, yield," akin to L. data, → datum).