<< < -gr eff Hes Kra Pen Ros > >>
-gram -negâšt (#) Fr.: -gramme A combining form meaning "something drawn, written" (diagram, spectrogram, oscillogram). From Gk. -gramma, combining form of gramma "something written or drawn," → graph. -Negâšt, from negâšt "drawn, written;" p.p. of negâštan, negârdan "to paint, write," → graph. |
acceleration parameter pârâmun-e šetâb Fr.: paramètre d'accéleration A measure of the departure from a constant rate of the acceleration of the Universe, expressed by: q(t) = R(t)R^{ ..}(t)/R^{ .}^{2}(t), where R(t) represents the size of the Universe at time t. Traditionally, a negative sign is inserted in the above equation for the → deceleration parameter. → acceleration; → parameter. |
Alderamin (α Cephei) Zerâ'-e Yamin Fr.: Alderamin The brightest star in → Cepheus and a → subgiant star of apparent visual magnitude 2.44. Its → spectral type is A7 and distance 49 → light-years. Alderamin, from Ar. al dhirâ' al-yamin "right arm" (of Cepheus), from Ar. dhirâ' "arm" + yamin "right". Zerâ'-e Yamin, from Ar. al dhira al-yamin. |
angular momentum parameter pârâmun-e jonbâk-e zâviye-yi Fr.: paramètre de moment angulaire The ratio J/M, where J is the → angular momentum of a → rotating black hole and M the mass of the black hole. |
Argand diagram nemudâr-e Argand Fr.: diagramme d'Argand A geometrical representation of → complex numbers, which like the → Cartesian coordinates, uses two reference perpendicular axes. The horizontal axis represents the → real number part of the number and the perpendicular axis the → imaginary number part. Named after Jean Robert Argand (1768-1822), a Swiss mathematician, who introduced this representation; → diagram. |
backup program barnâme-ye yadaki (#) Fr.: programme de remplacement An auxiliary observing program to be carried out at telescope in case the atmospheric conditions make the main program unfeasible. Backup, from → back + up; → program. Barnâmé, → program; yadaki "reserve, substitute," from yadak "a led horse." |
Baldwin-Phillips-Terlevich diagram nemudâr-e Baldwin-Phillips-Terlevich Fr.: diagram de Baldwin-Phillips-Terlevich A set of nebular → emission line diagrams used to distinguish the ionization mechanism of → nebular gas. The most famous version consists of [N II]λ6584/Hα versus [OIII] λ5007/Hβ. The next two more commonly used BPT diagnostics are [S II] λλ6717,6731/Hα versus [O III] λ5007/Hβ and [O I] λ6300/Hα versus [O III]λ5007/Hβ. These diagrams use strong, optical lines of close proximity in the ratios to limit → reddening and → spectrophotometric effects. They are able to clearly distinguish different classes of → ionization, for example → LINERs from normal → H II regions and → active galactic nuclei. Baldwin, J. A., Phillips, M. M., Terlevich, R., 1981 PASP 93, 5; → diagram. |
bias frame nurdâd barây-e varak Fr.: pose pour biais CCD frame with exposure time set to zero and giving the bias level. |
butterfly diagram nemudâr-e parvânevâr Fr.: diagramme en papillon A graph on which the latitudes of → sunspots are plotted against time. It shows how sunspots migrate from high latitudes (30°- 40° north or south) to the solar equator (latitude of about 5°) during each → solar cycle, according to → Sporer's law. The shape of these distributions, when represented for both hemispheres, resembles the wings of a butterfly. The diagram was first created by Edward W. Maunder in 1904 to illustrate the solar cycle (M.S.: SDE). Butterfly, from M.E. butterflye, from O.E. butorfleoge, from butor, butere "butter" floge "fly," but the etymology is not clear; → diagram. Nemudâr, → diagram; parvânevâr "resembling a butterfly," from parvâné "butterfly" + -vâr similarity suffix. |
CCD frame tak-tasvir-e sisidi Fr.: image CCD One of a series of astronomical images obtained using a CCD detector in particular for calibration purposes. |
color-color diagram nemudâr-e rang-rang (#) Fr.: diagramme couleur-couleur A diagram based on two photometric colors usually representing the same class of astronomical objects. → color; → diagram. |
color-luminosity diagram nemudâr-e rang-tâbandegi Fr.: diagramme couleur-luminosité A form of → Hertzsprung-Russell diagram in which the luminosity is the vertical axis and the → color index the horizontal axis. → color; → luminosity, → diagram. |
color-magnitude diagram nemudâr-e rang-borz Fr.: diagramme couleur-magnitude A form of → Hertzsprung-Russell diagram in which the visual absolute magnitude M_{v} is the vertical axis and the → color index the horizontal axis. |
comoving frame cârcub-e hamjonb Fr.: rérérentiel comobile A → reference frame that is attached to a moving object. The object in this frame is therefore at rest. |
conceptual diagram nemudâr-e begerti Fr.: schéma conceptuel Same as → concept map. → conceptual; → diagram. |
correlogram hambâzâneš-negâr Fr.: corrélogramme A plot showing a summary of correlation at different periods of time. Correlo-, from → correlation; → -gram. |
deceleration parameter pârâmun-e vâšetâb Fr.: paramètre de décéleration A parameter designating the rate at which the expansion of the Universe would slow down owing to the braking gravitational effect of the matter content of the Universe. It is expressed by: q(t) = -R(t)R^{ ..}(t)/R^{ .}^{2}(t), where R(t) represents the size of the Universe at time t. See also → expansion parameter; compare with → acceleration parameter. → deceleration; → parameter. |
density parameter pârâmun-e cagâli Fr.: paramètre de densité One of the four terms that describe an arranged version of the
→ Friedmann equations. They are all time dependent. |
diagram nemudâr (#) Fr.: diagramme A graphic representation of the behavior of one or several variables. From Fr. diagramme, from L. diagramma, from Gk. diagramma "that which is marked out by lines," from diagraphein "to mark out by lines," from dia- "across, out" + graphein "to write, draw," → -graphy. Nemudâr agent noun of nemudan "to show," → display, from the past stem nemud + -âr, such as xâstâr, foruxtâr, padidâr, parastâr (contraction of *parastidâr). |
Eddington parameter pârâmun-e Eddington Fr.: paramètre d'Eddington A → dimensionless parameter indicating the degree to which a star is close to the → Eddington limit. It is expressed as Γ = L / L_{Edd} = κ L / (4πGMc), where L and M are the star luminosity and mass respectively, κ is the opacity, c the speed of light, and G the → gravitational constant. At the Eddington limit, Γ = 1, the star would become unbound. Because stellar luminosity generally scales with a high power of the stellar mass (L∝ M^{3-4}), → massive stars with M larger than 10 Msun generally have electron Eddington parameters of order Γ ≅ 0.1-1. After Arthur Stanley Eddington (1882-1944), prominent British astrophysicist; → parameter. |
<< < -gr eff Hes Kra Pen Ros > >>