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

A sample in which every individual element in the population has an equal chance of being selected.

→ unbiased; → sample.

A stellar atmosphere model which ignores metals and their physical effects. → line-blanketed model; → line blanketing.

→ un-; → blanketed model.

1) Not bound or tied up.
2) Not held by a → chemical bond, → gravity, or other physical force (OxfordDictionaries.com).
See: → unbound charge, → unbound cluster, → unbound system.

→ un-; → bound.

Same as → free charge.

→ unbound; → charge.

A cluster of objects, such as stars or galaxies, in which the members are not tied together gravitationally. In such a cluster the members scatter through space following different directions. → bound cluster.

→ unbound; → cluster.

An association of bodies which are not gravitationally tied together.

→ unbound; → system.

A class of gravitationally loose stellar conglomerate with a notable apparent shape making it different from typical → bound  → star clusters. The UYSS class includes a large range of objects, which extend at various size scales and at various degrees of self-binding; from small (semi-)compact → unbound systems named → stellar associations, to huge extended superstructures of → massive stars that make up whole parts of Galactic → spiral arms, known as → stellar complexes (Gouliermis, D. A., 2018, PASP 130:072001; arXiv:1806.11541).

→ unbound; → young; → stellar; → system.

The function y = f(x) in a given range of the argument x if there is no number M such that for all values of x in the range under consideration the inequality | f(x) | ≤ M will be fulfilled. → bounded function.

→ unbound; → function.

The state of being uncertain; unpredictability; indeterminacy. → uncertainty principle.

→ un- + → certainty.

A quantum mechanical principle due to Werner Heisenberg which states that the position and momentum of a particle cannot be determined simultaneously with any arbitrary accuracy. These quantities can be determined only with accuracies limited by the relation Δx.Δp ≥ (1/2)ħ, where Δx is the error in the determination of the position and Δp is the error in the momentum. A similar relation holds for the energy of a particle and the time, ΔE.Δt ≥ (1/2)ħ. Same as → Heisenberg uncertainty principle.

→ uncertainty; → principle.

A temporary designation for a → B[e] star that cannot be placed in any of the four known classes.

→ classification; → B[e] star.

Difficult to see, hear, understand, or to be sure about.

→ un-; → clear.

Not limited by conditions; absolute.

→ un-; → conditional.

Not awake and aware; not responding to one's environment.

→ non-; → conscious.

The → state of being → unconscious.

→ unconscious; → -ness.

A dune on a planetary surface, used in plural form undae.

From L. unda "wave," cognate with → water.

Šen-tal, from šen "sand" + tal "hill, heap."

A prefixal use of under, as to indicate place or situation below or beneath. Contrary to → over-.

M.E., from O.E. (cf. O.H.G. untar, Ger. unter, Goth. undar), from PIE *ndhero- "lower;" cf. Av. aδara- (adj.), aδairi- (prep.) "below;" Mid.Pers. êr "below, down; low, under," adar "low," azêr "below, under" (Mod.Pers. zir "below, down"); Skt. ádhara- "lower;" O.E. under "under, among").

Kam- "little, few; deficient, wanting; scarce" (Mid.Pers. kam "little, small, few," O.Pers./Av. kamna- "small, few").

The abundance of a chemical element being lower than a reference value, in particular compared to that of the Sun.

→ under-; → abundance.

The behavior of a damped system when the amount of damping is weak so that the system oscillates with the amplitude gradually decreasing to zero. → overdamping.

→ under-; → damping.

1) To estimate at too low a value, rate, or the like.
2) An estimate that is too low. → overestimate.

→ under-; → estimate