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

The condition or quality of being earlier in time or occurrence, or being regarded as more important.

→ prior; → -ity.

1) General: The quality or fact of being probable. A strong → likelihood or chance of something.
2) Statistics: The branch of → mathematics that studies the possible outcomes of given events and their relative distributions. → probability theory.

From → probable + → -ity.

A curve that describes the distribution of probability over the values of a random variable.

→ probability; → curve.

A mathematical function whose integral over any interval gives the probability that a continuous → random variable has values in this interval. Also known as → density function, frequency function, → probability function.

→ probability; → density; → function.

The function that describes the range of possible values that a random variable can attain and the probability that the value of the random variable is within any (measurable) subset of that range.

→ probability; → distribution.

A function that represents a probability distribution in terms of integrals. Also called probability density function or density function.

→ probability; → function.

A branch of → mathematics with its own axioms and methods, which is based on the concept of → randomness and is concerned with the possible outcome of given → events and their relative → likelihoods and → distributions.

→ probability; → theory.

The → angular velocity of a star deduced from the → rotational broadening of its → spectral lines. It is expressed as v sini, where i is the → inclination of the rotational axis with respect to the normal to the → plane of the sky. The real equatorial rotational velocity can be determined only if the inclination of the rotational axis is known.

Projected, p.p. of → project; → rotational; → velocity.

Math.: A relationship bewteen two quantities such that if one quantity changes the other changes in the same proportion; denoted as y ∝ x.

→ proportional + → -ity.

Math.: A → constant that converts a proportionality into an → equation. Thus the proportionality constant k converts the proportionality y ∝ x into the equation y = kx.

→ proportionality + → constant.

1) Extensive mention in the news media or by word of mouth or other means of communication.
2) The state of being public, or open to general observation or knowledge (Dictionary.com).

→ public; → -ity.

A term used to describe irregularly spaced, fine-scale structure in optically thick rings. The process relies on a combination of viscosity and self-gravity of ring material to produce this fine structure. Also known as overstability (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ pulsational; → instability.

A → supernova resulting from the → pair instability that generates several successive explosions. According to models, a first pulse ejects many solar masses of hydrogen layers as a shell. After the first explosion, the remaining core contracts and searches for a stable burning state. When the next explosion occurs a few years later, several solar masses of material are again ejected, which collide with the earlier ejecta. This collision can radiate 10⁵⁰ erg of light, about a factor of ten more than an ordinary → core-collapse supernova. After each pulse, the remaining core contracts, radiates neutrinos and light, and searches again for a stable burning state. Later ejections have lower mass, but have higher energy. They quickly catch up with the first shell, where the collision dissipates most of their kinetic energy as radiation. The first SNe from → Population III stars are likely due to pulsational pair instability (Woosley et al. 2007, Nature 450, 390). See also → pair-instability supernova.

→ pulsational; → pair; → instability.

The degree to which → impurity is incorporated into a semiconductor material.

M.E., from O.Fr. pureté, from L.L. puritatem (nom. puritas) "cleanness, pureness," from purus "clean;" cf. Av. pūitika- "serving for purification," Mod.Pers. pâk "clean;" Skt. pavi- "to become clean," pávate "purifies, cleanses;" O.H.G. fouwen, fewen "to sift;" PIE base *peu- "to purify, cleanse."

Žâvi, noun from adj. žâv "pure."

A distinguishing characteristic, property, or attribute of something.
2) → image quality.
3) → sound quality.

M.E. qualite, from O.Fr. qualite (Fr. qualité), from L. qualitas, from qual(is) "of what sort?" + → -ity.

Cunâ, cuni, from Mid.Pers. cigôn "how?," cigônêh "nature, character," O.Pers/Av. ci- "what, any," collateral stem to ka- "who?, what?" (cf. Skt. ka-; Gk. po-; L. quo-; E. what, who; PIE *qwos/*qwes) + Av. gaona- "color" (Mid.Pers. gônak "kind, species").

The property of magnitude.
An entity having magnitude, size, extent, or amount.

M.E., from rom O.Fr. quantite (Fr. quantité), from L. quantitatem (nominative quantitas), from quant(us) "how much?" + -itas, → -ity.

Candâ, candi "quantity," Mid.Pers. candih "amount, quantity," from cand "how many, how much; so many, much;" O.Pers. yāvā "as long as;" Av. yauuant- [adj.] "how great?, how much?, how many?," yauuat [adv.] "as much as, as far as;" cf. Skt. yāvant- "how big, how much;" Gk. heos "as long as, until."

A theory of gravity, yet to be developed, that would properly include quantum mechanics. Because of the tensor nature of general relativity, it is not renormalizable as a field theory in perturbation from flat space. So far various attempts to quantize general relativity have been unsuccessful.

→ quantum; → gravity.

A property in → quantum mechanics whereby in a quantum system the sum of all probabilities of all possible outcomes must be 1. Quantum unitarity makes the modulous of a → quantum state invariant with time.

→ quantum. → unitary.

The component of a three-dimensional velocity vector of an object directed along the line of sight. It is measured by examining the Doppler shift of lines in the spectrum of astronomical objects.

→ radial; → velocity.

A curve describing the variation of the radial velocity of a star, due to the Doppler effect, under the gravitational effect of a secondary body (companion or exoplanet). The amplitude of these variations depends upon the mass of the secondary and its distance from the star.

→ radial velocity; → curve.