abarqul-e sorx (#)
Fr.: supergéante rouge
A supergiant star with spectral type K or M. Red supergiants are the largest stars in the Universe, but not necessarily the most massive. Betelgeuse and Antares are the best known examples of a red supergiant.
Fr.: énergie au repos
kâruž-e jerm-e âram
Fr.: énergie au repos
Same as → rest energy.
Fr.: énergie de rotation
Fr.: énergie rotationnelle
The → kinetic energy due to the → rotation of and object. Rotational energy is part of the total kinetic energy of the body. It is given by: (1/2)Iω2, where I is the → moment of inertia and ω is the → angular velocity. Same as → angular kinetic energy.
A unit of energy used in atomic physics, equal to about 13.6 electron-volts, the ionization potential of hydrogen.
In honor of the Swedish physicist Johannes Robert Rydberg (1854-1919), who did important contributions on spectroscopy, and in particular found a relatively simple expression relating the various lines in the spectra of chemical elements (1890).
pâyâ-ye Rydberg (#)
Fr.: constante de Rydberg
A fundamental constant of atomic physics appearing in the → Rydberg formula. The Rydberg constant for hydrogen is 109,739 cm-1.
Fr.: correction de Rydberg
A term inserted into a formula for the energy of a single electron in the outermost shell of an atom to take into account the failure of the inner electron shells to screen the nuclear charge completely.
Fr.: formule de Rydberg
A formula, used in atomic physics, which describes the wavelengths or frequencies of light in various series of related spectral lines, such as those emitted by hydrogen atoms.
Fr.: limite de Schönberg-Chandrasekhar
During the → main sequence stage, a star burns the hydrogen in its core and transforms it into helium. When the helium mass amounts to about 10% of the initial stellar mass, the star can no longer maintain the → hydrostatic equilibrium in its core; the star increases its volume and leaves the main sequence in order to become a → red giant.
Named after the Brazilian astrophysicist Mario Schönberg (1914-1990) and Subramahmanyan Chandrasekhar, → Chandrasekhar limit, who were the first to point out this limit and derive it (1942, ApJ 96, 161).
semiempirical binding energy formula
disul-e nime-ârvini-ye kâruž-e bandeš
Fr.: formule semi-empirique de l'énérgie de liaison
Same as → Weizsacker formula.
Fr.: énergie de séparation
The energy required to remove a particle (a proton or a neutron) from a particular atomic nucleus.
Fr.: critère de Solberg-Høiland
A criterion for → convective stability in → massive stars. The Solberg-Høiland stability criterion corresponds to the inclusion of the effect of → rotation (variation of → centrifugal force) in the convective stability criterion. It is a combination of → Ledoux's criterion (or possibly → Schwarzschild's criterion) and → Rayleigh's criterion. Both the dynamical shear and Solberg-Høiland instabilities occur in the case of a very large → angular velocity decrease outwards. Therefore, in a → rotating star the Ledoux or Schwarzschild criteria for convective instability should be replaced by the Solberg-Høiland criterion. More specifically, this criterion accounts for the difference of the centrifugal force for an adiabatically displaced fluid element. It is also known as the axisymmetric baroclinic instability. It arises when the net force (gravity + buoyancy + centrifugal force) applied to a fluid parcel in an adiabatical displacement has components only in the direction of the displacement (A. Maeder, Physics, Formation and Evolution of Rotating Stars, 2009, Springer).
E. Høiland, 1939, On the Interpretation and Application of the
Circulation Theorems of V. Bjerknes. Archiv for mathematik og
naturvidenskab. B. XLII. Nr. 5. Oslo.
Fr.: énergie acoustique
The energy which → sound waves impart to a medium. Same as acoustic energy.
spectral energy distribution (SED)
vâbâžeš-e kâruž-e binâbi
Fr.: distribution de l'énergie spectrale
A plot showing the energy emitted by a source as a function of the radiation
wavelength or frequency. It is used in many branches of astronomy to characterize
astronomical sources, in particular mainly in → near infrared
and → middle infrared to study
→ protostars or
→ young stellar objects. The SED of these objects is
divided in four classes.
splitting of energy level
fâqeš-e tarâz-e kâruž
Fr.: dédoublement d'un niveau d'énergie
1) marcidan; 2) marcândan
1) To sink or plunge under water or beneath the surface of any enveloping medium.
From L. submergere, from → sub- + mergere "to dip, immerse;" probably by rhotacism from PIE *mezg- "to dip, plunge;" cf. Skt. majj- "to sink in water;" Lith. mazgoju "to wash."
Marcidan, from Av. mraoc- "to float, submerge;" cf. Skt. mroc/mloc "to go down, set (of the Sun), to disappear, to hide;" Kurd., Laki, Nahâvandi, Bovir-Ahmadi mala- "swim," Kurd. melâna "ship, boat," melaq "wave" may be related to this Av. form.
supergalactic coordinate system
râžmân-e hamârâhâ-ye abarkahkašâni
Fr.: système des coordonnées supergalactiques
A spherical → coordinate system in which the → equator is the → supergalactic plane. Supergalactic longitude, SGL, is measured → counterclockwise from direction l = 137.37 deg, b = 0 deg (between 0 and 360 deg). The zero point for supergalactic longitude is defined by the intersection of this plane with the → Galactic plane. In the → equatorial coordinate system (J2000) this is approximately 2.82 h, +59.5 deg. Supergalactic latitude, SGB, is measured from the supergalactic plane, positive northward and negative southward. The North Supergalactic Pole (SGB=90 deg) lies at galactic coordinates l = 47.37 deg, b = +6.32 degrees, corresponding to the equatorial coordinate system (J2000) 18.9 h, +15.7 deg.
Fr.: latitude supergalactique