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.
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.
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.
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.
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.
Fr.: diagramme couleur-magnitude
A form of → Hertzsprung-Russell diagram in which the visual absolute magnitude Mv is the vertical axis and the → color index the horizontal axis.
Fr.: schéma conceptuel
Same as → concept map.
→ conceptual; → diagram.
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).
Fr.: diagramme de Feynman
A schematic representation, in quantum electrodynamics and quantum chromodynamics, of the way elementary particles like electrons and protons interact with each other by exchanging photons. Use of Feynman diagrams can greatly reduce the amount of computation involved in calculating a rate or cross section of a physical process.
After the American physicist Richard P. Feynman (1918-1988), Nobel prize 1965; → diagram.
Fr.: diagramme H-R
Same as → Hertzsprung-Russell diagram.
Short for → Hertzsprung-Russell diagram.
nemudâr-e Hertzsprung-Russell (#)
Fr.: diagramme de Hertzsprung-Russell
A display of stellar properties using a plot of
→ effective temperature (or instead
→ color or → spectral type)
along the abscissa versus
(or → absolute magnitude). The temperature is plotted
in the inverse direction, with high temperatures on the left and low temperatures on
the right. On the diagram the majority of stars are concentrated in a diagonal strip running
from upper left to lower right, i.e. from high temperature-high luminosity
→ massive stars to low
temperature-low luminosity → low-mass stars.
This feature is known as the
→ main sequence. This is the locus of stars burning hydrogen in
their cores (→ proton-proton chain).
The lower edge of this strip, known as the
→ zero age main sequence (ZAMS), designates the positions
where stars of different mass first begin to burn hydrogen in their cores. Well below
the main sequence there is a group of stars that, despite
being very hot, are so small that their luminosity is very small as a
consequence. These are the class of → white dwarfs.
These objects represent old and very evolved
stars that have shed their outer layers to reveal a very small but
extremely hot inner core. They are no longer generating energy
but are merely emitting light as they cool
(→ white dwarf cooling track).
Stars with high luminosities but relatively low temperatures occupy a wide region
above the main sequence. The majority of them have used up all
the hydrogen in their cores and have expanded and cooled as a result of internal
readjustment. Called → red giants, they are still
burning helium in their cores (→ helium burning,
→ carbon burning).
There are also stars with very high luminosities, resulting from their
enormous outputs of energy, because they are burning their fuel at a prodigious rate.
These are the → supergiants. They can be hot or cool,
hence blue or red in color. Same as → H-R diagram.
Named after the Danish Ejnar Hertzsprung (1873-1967) and the American Henry Norris Russell (1877-1957). However, the first H-R diagram was published not by Hertzpurung neither Russell, but by a PhD student of Karl Schwarzschild at Göttingen. The student was Hans Rosenberg (1879-1940), who in 1910 published the diagram for stars in the → Pleiades (Astronomische Nachrichten, Vol. 186 (4445), p. 71, 1910). Although Hertzpurung had a very preliminary diagram in 1908, his first proper diagram was published in 1911. Likewise, Russell published his version only in 1915 with the better and more numerous data then available (Nielsen, A.V., 1969, Centaurus 9, 219; Valls-Gabaud, D., 2002, Observed HR diagrams and stellar evolution, ASP Conf. Proceedings, Vol. 274. Edited by Thibault Lejeune and João Fernandes); → diagram.
Fr.: diagramme de Hess
A diagram showing the relative density of occurrence of stars at various → color-magnitude positions of the → Hertzsprung-Russell diagram for a given → galaxy.
Named after R. Hess who originated it in 1924: "Die Verteilungsfunktion der absoluten Helligkeiten in ihrer Abhängigkeit vom Spektrum". Probleme der Astronomie. Festschrift fur Hugo v. Seeliger. Springer, Berlin. p. 265; → diagram.
nemudâr-e Hubble (#)
Fr.: diagramme de Hubble
A plot of the → redshift of galaxies against their distance or against their → apparent magnitude.
Fr.: diagramme de Hunter
A diagram where the surface → nitrogen → chemical abundance of stars is plotted against their → projected rotational velocity (v sini).
I. Hunter et al., 2009, A&A, 496, 841; → diagram.
Fr.: diagram de Jablonski
An energy schematic representing the → electronic states of a → molecule and the → transitions between them. The vertical axis shows energies whereas → energy states are grouped horizontally according to their spin → multiplicity. Radiation-less transitions are symbolized by usual arrows, while → radiative transitions are represented by wavy arrows. The vibrational ground states of each electronic state are indicated with thick lines and the higher → vibrational states with thinner lines.
Named after Aleksander Jablonski (1898-1980), a Polish physicist who was an expert in the field of luminescence and atomic optics; → diagram.
Fr.: diagramme de Kiel
A version of the → H-R diagram displaying stellar gravities (→ gravity, log g) against the corresponding → effective temperatures (Teff).
Named after the group of astrophysicists (W.-R. Hamann, W. Schmutz, U. Wessolowski) working at Kiel University (Germany), who introduced the diagram in 1980s; → diagram.
Fr.: diagrame de Kippenhahn
A plot representing the evolution of the internal structure of a star as a function of time. The x-axis indicates the time, the y-axis the mass, and a color or shading specifies convective regions. A vertical line through the graph corresponds to a model at a particular time.
Named after Rudolf Kippenhahn (1926-), a German astrophysicist; → diagram
Fr.: diagramme de Kruskal
A diagram used to plot trajectories in → space-time near a → black hole. The vertical and horizontal axes are two complicated functions of time and distance from the black hole. Lines of constant time radiate from the origin of the diagram, with steeper slopes corresponding to later times. Lines of constant distance are hyperbolas, lines of constant time pass through the origin; photons always travel along diagonal lines at ±45° to the vertical. The trajectory of an object falling into the black hole is shown as a curving line moving upward on the diagram at less than 45° to the vertical.
Named after the American physicist Martin David Kruskal (1925-2006); → diagram.
Fr.: diagramme logique
A diagram that uses special symbols called logic symbols to represent the detailed functioning of electronic logic circuits. The symbols do not represent the type of electronics used, but only their functions.
Fr.: diagramme de Minkowski
Same as → space-time diagram.
→ Minkowski metric; → diagram.