An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 29 Search : temperature
absolute temperature
  دما‌ی ا َوَست   
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
  زینه‌ی ِ دمای ِ بی‌دررو   
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 = CP / CV. 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
  دما‌ی ِ آنتن   
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
  دما‌ی ِ سیه‌جسم   
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
  دما‌ی ِ درخشندگی   
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
  دمای ِ رنگ   
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
  دمای ِ کوری   
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
  دمای ِ دبی   
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
  دمای ِ غبار   
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
  دمای ِ ا ُسکرمند   
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
  دمای ِ اینشتین   
damâ-ye Einstein (#)

Fr.: température d'Einstein   

A characteristic parameter occurring in the → Einstein model of → specific heats.

Einstein; → temperature.

electron temperature
  دمای ِ الکترونی   
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).
2) In the → solar wind, the temperature derived from the mean → thermal agitation of the electrons. More specifically, electric field receivers on board space probes carry out the spectroscopy of the → thermal noise due to the potential fluctuations produced by the thermal agitation of the electrons, yielding the electron temperature in certain conditions (N. Meyer-Vernet, 2007, Basics of the Solar Wind, Cambridge Univ. Press). See also → proton temperature.

electron; → temperature.

excitation temperature
  دمای ِ بر‌‌انگیزش   
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: Nu/Nl = (gu/gl) exp (-ΔE/kTex), where Nu and Nl are the upper level and lower level populations respectively, gu and gl the statistical weights, ΔE = hν the energy difference between the states, k is → Boltzmann's constant, and hPlanck's constant. The higher the energy of the occupied states, the higher the excitation temperature.

excitation; → temperature.

Hawking temperature
  دمای ِ هاؤکینگ   
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 TH = ħc3/(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 be approximately be written as: TH≅ 6.2 x 10-8 (Msun/M) K. Thus radiation from a solar mass black hole would be exceedingly cold, about 5 x 107 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 1015 g would have TH≅ 1011 K.

Hawking radiation; → temperature.

Hayashi temperature
  دمای ِ هایاشی   
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
  دمای ِ گیرانش   
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
  دمای ِ جنبشی   
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
  دمای ِ نوفه   
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
  دمای ِ پروتونی   
damâ-ye protoni

Fr.: température protonique   

The temperature in the → solar wind, as derived from the mean kinetic energy of protons: mv2/2 = (3/2)kTp, 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
  دمای ِ تابش   
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.

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