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

Of, relating to, or being the → unification of → electromagnetism and the → weak interaction.

→ electro-; → weak.

A period in the early history of the Universe lasting from 10^-36 to 10^-12 seconds after the → Big Bang. The electroweak epoch begins at the same time as cosmic → inflation is triggered. This is also the time when the → strong force breaks from the → grand unified force and ends with another → phase transition will occur in which the → weak interaction breaks from the → electroweak force.

→ electroweak; → epoch.

The force that takes part in an → electroweak interaction.

→ electroweak; → force.

The unified description of two of the four fundamental interactions of nature, → electromagnetism and the → weak interaction which would merge into a single force under conditions of extreme temperature (above 10¹⁶ degrees, 10² GeV) prevalent in the early history of the → Universe.

→ electroweak; → interaction.

A postulated type of star that could form toward the end of a → massive star's life, after → nuclear fusion has stopped in its → core, and before the star → collapses into a → black hole. In those → extreme conditions, when → temperature and → density inside the star are very high, → quarks could convert into → leptons. Hence huge amounts of energy can be released, much of which would be in the form of → neutrinos.

→ electroweak; → star.

A → chemically peculiar star with very weak helium lines. Examples include 3 Sco, HD 176582, HD 217833, HR 2949, and HD 21699. The He-weak stars do not form a homogeneous group. Some of them display intense Si, or Ti and Sr lines, and are considered a hot extension of the magnetic → Ap/Bp stars. Others show overabundances of P and Ga, typically noted for → HgMn stars. The star HD 139160 belongs to the non-magnetic subgroup of He-weak stars.

→ helium; → weak; → line.

Not powerful or intense.
→ electroweak epoch, → electroweak force, → electroweak interaction, → weak anthropic principle, → weak arm spiral galaxy, → weak emission-line central star, → weak encounter, → weak equivalence principle, → weak force, → weak gravitational lensing, → weak interaction, → weak lensing, → weak nuclear force, → weak wind problem, → weak-line T Tauri star, → weak-wind O-type star.

From O.N. veikr "weak," cognate with O.E. wac "weak, pliant, soft," from P.Gmc. *waikwaz "yield," *wikanan "bend" (cf. Du. week "weak, soft, tender," O.H.G. weih "yielding, soft," Ger. weich "soft," from PIE base *weik- "to bend, wind"

Nezâr "weak, feeble, thin, slim; flesh without fat" (bâde-ye nezâr "a wine with minute alcohol," soxan-e nezâr "inconsistent, weak statement"), variant zâr, Mid.Pers. nizâr (prefixed *ni- + *zâr/*zar) "weak, feeble," Mid./Mod.Pers. zarmân "old man, deterioration," Av. zairina- "exhausting, slackening," zaurura- "weak through old age, decrepit," cf. Skt. jára- "wearing out, exhaustion," jaranā- "old, decayed," jarimán- "weakness through old age," Gk. geron "old man," L. granum "grain;" PIE base *ger- "wear away."
Tâm, → faint.
Sost, from Mid.Pers. sust "weak, lazy."
Kamnur, from kam "little, few; deficient, wanting; scarce" (Mid.Pers. kam "little, small, few," O.Pers./Av. kamna- "small, few") + nur, → light.
Kamzur, from ham + zur, → strength.

A version of the → anthropic principle whereby the initial conditions in the → Universe are → constrained by the fact that → intelligent life has appeared.

→ weak; → anthropic; → principle.

A gas-rich galaxy that has weak stellar → spiral arms with → interarm gas and star formation more important than a typical → spiral galaxy, such as NGC 4414.

→ weak; → arm; → spiral; → galaxy.

A member of a class of cntral stars of planetary nebula, → CSPN, which have weaker and narrower emission lines than → Wolf-Rayet-like CSPNe (Tylenda et al. 1993, A&AS 102, 595).

→ weak; → emission; → line.

In a → star cluster, an → encounter that occurs at a distance and produces only very small changes in a star's velocity.

→ weak; → encounter.

All structureless bodies fall along the same → path in a → gravitational field, independent of their composition. Also known as → universality of free fall. See also: → equivalence principle, → Einstein equivalence principle.

→ weak; → equivalence; → principle.

Same as → weak interaction.

→ weak; → force.

A gravitational bending of light by structures in the Universe that distorts the images of distant galaxies. The distortion allows the distribution of → dark matter and its evolution with time to be measured, thereby probing the influence of → dark energy on the growth of structures. Weak gravitational lensing is generally difficult to identify in individual images, in contrast to → strong gravitational lensing (see, e.g., Bartelmann & Peter Schneider, 2001, Phys. Rept. 340, 291).

→ weak; → gravitational; → lensing.

One of the fundamental forces of nature that accounts for some particle interaction, such as → beta decay (→ radioactivity), the decay of free → neutrons, → neutrino interactions, and so forth. It is short-ranged, dominating at distances of 10^-16 cm and occurs at a rate slower than that of the → strong interaction by a factor of about 10^-13, hence its name. Although the weak interaction also includes interactions in which no neutrinos are emitted, neutrino emission accompanies all weak interactions of interest to astrophysics. Weak interaction plays an important role in the evolution of the stars from birth to death. For example, the → proton-proton reaction is a weak interaction. Also called → weak force or → weak nuclear force.

→ weak; → interaction.

The → gravitational lensing in which the images are only weakly distorted, and do not form wide arcs or multiple image systems. This happens if the → gravitational lens mass in front of a source is not concentrated enough to form multiple images. The resulting small distortions cannot be seen on individual sources, as we do not know their unlensed, "intrinsic" shape. However, if an entire population of background sources is available, the distortions can be revealed, either statistically or by local averaging. See also → strong lensing.

→ weak; → lensing.

Same as → weak interaction.

→ weak; → nuclear; → force.

The discrepancy between the observed → mass loss rates and the predicted values for → weak-wind O-type stars.

→ weak; → wind; → problem.

A T Tauri star that lacks strong emission lines in its optical spectrum, and lacks both strong → stellar wind and → infrared excess. These objects are believed to be → pre-main sequence stars without obvious signs for disk → accretion. Weak-line T Tauri stars result from the evolution of → classical T Tauri stars.

→ weak; → line; → T Tauri star.

A → main sequence → O star with low luminosity and surprisingly weak → stellar wind compared to "classical" dwarfs. The → mass loss rates are lower than 10^-8 solar masses per year and the → modified wind momenta nearly 2 orders of magnitude smaller than that expected from wind models for typical O stars. Weak-wind O-type stars occur in both → metal-rich and → metal-poor environments. Their nature is not yet fully understood. same as → weak wind problem.

→ weak; → wind; → O-type star.