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

1) Nourishing; providing nourishment or nutriment.
2) Containing or conveying nutriment, as solutions or vessels of the body.
3) A nutrient substance (Dictionary.com).

From L. nutrientem, pr.p. of nutrire, → nourish.

Fârmand, from present stem of fâridan, + -mand.

1) Any substance or matter that, taken into a living organism, serves to sustain it in its existence, promoting growth, replacing loss, and providing energy.
2) Anything that nourishes; nourishment; food (Dictionary.com).

From L. nutrimentum "nourishment; support," from nutrire, → nourish.

Fârâk, from present stem of fâridan, → nourish, + -âk (as in xorâk, pušâk, etc.).

1) The act or process of nourishing or of being nourished.
2) The science or study of, or a course of study in, nutrition, especially of humans (Dictionary.com).

Verbal noun from L. nutrire, → nourish.

A person who is trained or expert in the science of nutrition.

→ nutrition; → -ist.

1) Serving to nourish; providing nutriment; nutritious.
2) Of, pertaining to, or concerned with nutrition (Dictionary.com).

Adjective and agent noun from L. nutrire, → nourish.

Same as → night blindness; opposite of → hemeralopia.

L.L. nyctalopia, from Gk. nukt, → night + al(aos) "blind" + -opia, akin to ope "view, look," ops "eye."

Šabkuri, from šab, → night, + kuri "blindness," from kur, → blind.

The mean square noise voltage across a resistance in thermal equilibrium is four times the product of the resistance, Boltzmann's constant, the absolute temperature, and the frequency range within which the voltage is measured. → Johnson-Nyquist noise.

Named after Harry Nyquist (1889-1976), a Swedish-born American physicist, who made important contributions to information theory. → Johnson-Nyquist noise; → formula.

The highest frequency that can be determined in a Fourier analysis of a discrete sampling of data.

→ Nyquist formula; → frequency.

The minimum number of resolution elements required to properly sample a signal, such as a star image, without causing erroneous effects known as aliasing. For electronic imaging, this number is generally taken as 2 pixels across the seeing disk diameter at the half intensity points. Also called → Shannon's sampling theorem and → sampling theorem.

Named after Harry Nyquist (1889-1976), a Swedish-born American physicist, who made important contributions to information theory, and Claude Elwood Shannon (1916-2001), an American mathematician and pioneer of information theory; → theorem.

A luminous, hot, blue star whose spectrum is dominated by the lines of hydrogen, atomic helium, and ionized helium; also known as O-type star. This is the earliest → spectral type and the only → main sequence star in which ionized helium is present. The → effective temperatures of these stars range from about 30,000 K to 50,000 K, their luminosities from 50,000 to 1,000,000 times that of → solar luminosity, and their masses from about 20 to 100 → solar masses. The hottest O-type stars display high ionization emission features such as N III and He II, → Of star. They are divided into subtypes O2, the hottest, to O9.7, the coldest. O-type stars are relatively rare, for each star of 100 solar masses there are 10⁶ stars of solar mass. They are relatively short-lived since they spend only a few million years on the main sequence. The brightest O-type star in the sky visible with naked eye is → Alnitak. For prominent Galactic O stars see → HD 93129.

O, letter of alphabet used in the Harvard spectral classification; → star.

The circular configuration of magnetic field lines around a → magnetic null point. See also → X-point.

O, the round letter of alphabet; → point.

Same as → O star.

O, letter of alphabet used in the → Harvard classification; → type; → star.

A loosely bound grouping of O and B stars that typically stretches up to several hundred → light-years and may contain between a dozen and several hundred → O stars and → B stars. The members of an OB association are young and of roughly the same age. OB associations dissipate in a few tens of millions of years.

O and B, from spectral types; → association.

A collective designation for massive O and B stars.

→ O star; → B star.

A hot star belonging to one of the two groups of → EHB stars or → pre-WD stars.

→ OB star; → subdwarf.

A → carbon (C)-rich → O-type or → B-type star.

→ O star; → B star; → carbon; → star.

The symbol ÷ used to indicate → division. This symbol was first used as a → division sign by Johann Rahn (or Rhonius) (1622-1676) in 1659 in Teutsche Algebra.

From Gk. obelus "sharpened stick, spit, pointed pillar," related to obelisk, originally used in ancient manuscripts to mark passages that were suspected of being corrupted, doubtful, or spurious.

→ division sign.

The outermost of Uranus' large satellites and the second largest. It has a diameter of 523 km and orbits 583,420 km from its planet. Compared to Uranus' moons Ariel, Titania, and Miranda, Oberon is heavily cratered. Like all of Uranus' large moons, Oberon is composed of roughly half ice and half rock. Oberon was discovered by Herschel in 1787.

Oberon is the King of the Fairies and husband of Titania in Shakespeare's Midsummer-Night's Dream.

1) General: Anything that is visible or tangible.
2) Physics: A collection of masses, taken to be one.
3) Optics: The collection of points that acts as a source of light rays for an optical system.
4) Astro.: A general designation for material bodies studied in this science.
5) Math.: Anything that could be formally defined, and with which one may do deductive reasoning and mathematical proofs. → mathematical object
6) Computer science: A free standing chunk of code that defines the properties of some thing.
7) Grammar: In English grammar, a noun, noun phrase, or pronoun that is affected by the action of a verb (a direct object or an indirect object) or that completes the meaning of a preposition (the object of a preposition).
8) To raise or state an argument against.

From M.L. objectum "thing thrown down or put before" (the mind or sight), neutral of objectus, p.p. of obicere "to present, oppose, cast in the way of," from ob "against" + jacere "to throw," from PIE base *ye- "to do" (cf. Gk. iemi, ienai "to send, throw," Hitt. ijami "I make").

Barâxt "thing drawn against, before" from bar- + âxt. The prefix bar- "on; upon; against; before; at; in," from Mid.Pers. abar, O.Pers. upariy "above; over, upon, according to," Av. upairi "above, over" (upairi.zəma- "located above the earth"), cf. Gk. hyper- "over, above," L. super-, O.H.G. ubir "over;" PIE base *uper "over".
The second component âxt, contraction of âxté, p.p. of âxtan, variants âhixtan, âhiz- "to draw (a sword)," âhanjidan "to draw up, pull, extract," Mid.Pers. âhixtan, âhanjitan "to draw out, pull up, extract," Av. θanj- "to draw, pull, drive;" Proto-Iranian *θanj-.
Kondâr, literally "action receiver," from kon- present stem of kardan "to do, make," → -or, used as action noun (like xor, xâb, foruš), + dâr agent noun from dâštan "to receive" (Dehxodâ), originally "to have, hold, possess," → property.

The → lens or lenses in the → object end of the body tube of a → microscope, by means of which the rays coming from the object examined are brought to a focus. Same as → objective. An old term for the → objective lens of a → refracting telescope.

→ object; → glass.