absolute temperature damâ-ye avast Fr.: température absolue The value of a → temperature in the → Kelvin scale. The absolute temperature is equal to the temperature on the → Celsius scale -273.16 °C. → absolute; → temperature. |
adiabatic temperature gradient zine-ye damâ-ye bidarrow Fr.: gradient de température adiabatique The temperature gradient defining the → radiative equilibrium condition in a region. It is expressed as: dT/dr = (1 - 1/ γ)((T / P)(dP / dr), where T and P are temperature and pressure, dT / dr and dP / dr temperature and pressure gradients respectively, and γ = C_{P} / C_{V}. For radiative equilibrium to be stable against → convection, the actual temperature gradient must be less than the adiabatic temperature gradient, i.e. |dT /dr|_{rad} < |dT /dr|_{ad}. See also → Schwarzschild's criterion. → adiabatic; → temperature; → gradient. |
antenna temperature damâ-ye ânten Fr.: température d'antenne In radio astronomy, a measure of the power absorbed by the antenna. In an ideal, loss-free radio telescope, the antenna temperature is equal to the brightness temperature if the intensity of the received radiation is constant within the main lobe. → antenna; → temperature. antenna; → temperature. |
blackbody temperature damâ-ye siyah-jesm (#) Fr.: température de corps noir The temperature at which a blackbody would emit the same radiation per unit area as that emitted by a given body at a given temperature. → blackbody; → temperature. |
brightness temperature damâ-ye deraxšandegi Fr.: température de brillance In radio astronomy, the temperature of a source calculated on the assumption that it is a blackbody emitting radiation of the observed intensity at a given wavelength. → antenna temperature. → brightness; → temperature. |
color temperature damâ-ye rang Fr.: température de couleur The temperature of that black-body which has the same spectral energy distribution in a limited spectral region, as the object under study has. → color; → temperature. |
Curie temperature damâ-ye Curie (#) Fr.: température de Curie The highest temperature for a given → ferromagnetic substance above which the → magnetization is lost and the substance becomes merely → paramagnetic. The Curie temperature of iron is about 1043 K and that of nickel 631 K. Named after the French physicist Pierre Curie (1859-1906), a pioneer in magnetism, crystallography, and radioactivity. In 1903 he received the Nobel Prize in Physics with his wife Marie Curie (1867-1934, née Maria Skłodowska), and Henri Becquerel (1852-1908); → temperature. |
Debye temperature damâ-ye Debye (#) Fr.: température de Debye The characteristic → temperature of the → crystal as given by the → Debye model of → specific heats. → debye; → temperature. |
dust temperature damâ-ye qobâr Fr.: température de poussière An indication of the heat amount received by → dust grains from the ambient → radiation field. Dust temperature depends on the optical properties and → sizes of grains (i.e., on the way they → absorb and → emit radiation) as well as on the → interstellar radiation field. Most of the visible and → ultraviolet radiation in galaxies from stars passes through clouds of particles and heats them. This heating leads to re-radiation at much longer wavelengths extending to the millimeter. → dust; → temperature. |
effective temperature damâ-ye oskarmand Fr.: température effective A measure of the surface temperature of a star derived from the total emitted energy, assuming that the star is a → blackbody emitter (→ Stefan-Boltzmann law, → Planck's radiation law). See also → brightness temperature; → color temperature. → effective; → temperature. |
Einstein temperature damâ-ye Einstein (#) Fr.: température d'Einstein A characteristic parameter occurring in the → Einstein model of → specific heats. → Einstein; → temperature. |
electron temperature damâ-ye elektroni (#) Fr.: température électronique 1) The temperature of electrons in an interstellar ionized nebula (e.g. in
→ H II regions and
→ planetary nebulae) as determined by characteristic
→ emission lines (optical
→ forbidden lines or
→ radio recombination lines). → electron; → temperature. |
excitation temperature damâ-ye barangizeš Fr.: température d'excitation Of a gas or plasma, the temperature deduced from the → populations of atomic → excited states, as expressed by the Boltzmann formula: N_{u}/N_{l} = (g_{u}/g_{l}) exp (-ΔE/kT_{ex}), where N_{u} and N_{l} are the upper level and lower level populations respectively, g_{u} and g_{l} the statistical weights, ΔE = hν the energy difference between the states, k is → Boltzmann's constant, and h→ Planck's constant. The higher the energy of the occupied states, the higher the excitation temperature. → excitation; → temperature. |
Hawking temperature damâ-ye Hawking Fr.: température de Hawking The temperature inferred for a → black hole based on the → Hawking radiation. For a → Schwarzschild black hole, one has T_{H} = ħc^{3}/(8πGMk) where ħ is the → reduced Planck's constant, c is the → speed of light, G is the → gravitational constant, M is the mass, and k is → Boltzmann's constant. The formula can approximately be written as: T_{H}≅ 6.2 x 10^{-8} (Msun/M) K. Thus radiation from a solar mass black hole would be exceedingly cold, about 5 x 10^{7} times colder than the → cosmic microwave background. Larger black holes would be colder still. Moreover, smaller black holes would have higher temperatures. A → mini black hole of mass about 10^{15} g would have T_{H}≅ 10^{11} K. → Hawking radiation; → temperature. |
Hayashi temperature damâ-ye Hayashi Fr.: température de Hayashi The minimum → effective temperature required for a → pre-main sequence star of given mass and radius to be in → hydrostatic equilibrium. This temperature delimits the boundary of the → Hayashi forbidden zone. → Hayashi track; → temperature. |
ignition temperature damâ-ye girâneš Fr.: température d'inflammation The minimum temperature to which a fuel must be heated in order to initiate self sustained combustion independent of another heat source. → ignition; → temperature. |
kinetic temperature damâ-ye jonbeši (#) Fr.: température cinétique The temperature of a gas defined in terms of the average kinetic energy of its atoms or molecules. → kinetic; → temperature. |
noise temperature damâ-ye nufé Fr.: température de bruit A means for specifying the noise generated as unwanted → electromagnetic radiation in a receiver system or one of its components. It is usually measured in terms of the equivalent temperature in a → Rayleigh-Jeans spectrum. Noise temperature is used mainly in radio astronomy. → noise; → temperature. |
proton temperature damâ-ye protoni Fr.: température protonique The temperature in the → solar wind, as derived from the mean kinetic energy of protons: mv^{2}/2 = (3/2)kT_{p}, where k is → Boltzmann's constant. There are two types of proton temperature: parallel temperature, measured from protons moving parallel to the magnetic field, and perpendicular temperature relating to protons at right angles to the magnetic field. The proton temperature is usually derived using particle detectors on board space probes that determine the velocity → distribution function of the particles from their energies (N. Meyer-Vernet, 2007, Basics of the Solar Wind, Cambridge Univ. Press). See also → electron temperature. → proton; → temperature. |
radiation temperature damâ-ye tâbeš Fr.: température de rayonnement The temperature of a source calculated assuming that it behaves as a → blackbody that radiates with the same intensity at the same frequency. Compared to the → effective temperature, the radiation temperature is measured over a narrow region of the → electromagnetic spectrum. → radiation; → temperature. |