An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



Number of Results: 16 Search : shock
accretion shock
  تش ِ فربال   
toš-e farbâl

Fr.: choc d'accrétion   

A → shock wave occurring at the surface of a compact object or dense region that is accreting matter with a → supersonic velocity from its environment. In the case of → young stellar objects the process is believed to take place by funneled streams in the form of → accretion columns that originate in the surrounding → accretion disk and flow along the → field lines of the → protostar → magnetosphere. The gas falls supersonically onto the surface of the central body and its impact produces strong shocks of a few million → kelvin, a phenomenon that is observable in → X-rays.

accretion; → shock.

adiabatic shock
  تش ِ بی‌دررو   
toš-e bidarrow

Fr.: choc adiabatique   

A → shock wave without → radiative cooling. The term "adiabatic" refers to the fact that no → heat is removed during shock.

adiabatic; → shock.

bow shock
  فرال-تش، فرال-شوک   
farâl-toš farâl-šok

Fr.: choc de proue   

A → shock wave created in front of an object moving through a medium with a velocity higher than that of the → sound waves in that medium. See, for example, → magnetosphere.

bow; → shock.

forward shock
  تش ِ پیش-سو   
toš-e piš-su

Fr.: choc en avant   

A highly → supersonic → shock wave created in a → supernova remnant as the expanding stellar ejecta runs into the → interstellar medium (ISM). This forward shock wave produces sudden, large changes in pressure and temperature behind the shock wave. The forward shock wave also accelerates electrons and other charged particles to extremely high energies. The forward shock front has a velocity of 104 km s-1 and can heat the shocked gas to temperatures ~ 109 K. While the forward shock continues to expand into the ISM, it creates a → reverse shock that travels back into the freely expanding → supernova ejecta.

forward; → shock.

oblique shock
  تش ِ یکور   
toš-e yekvar

Fr.: choc oblique   

A → shock wave that is inclined to the flow direction. Depending on the shape of the object and the speed of the → flow, the shock wave may be inclined to the flow direction.

oblique; → shock.

radiative shock
  تش ِ تابشی، شوک ِ ~   
toš-e tâbeši, šok-e ~

Fr.: choc radiatif   

A → shock wave in which the → time-scale for → cooling is much shorter than the appropriate → dynamical or → evolutionary time-scale of the system that drives the shock. Radiative shock waves are believed to play a key role in a variety of different astrophysical environments, including → magnetic cataclysmic variables, → jets from → young stellar objects, → accretion in → T Tauri stars, → colliding stellar winds, and → supernova remnants.

radiative; → shock.

reverse shock
  تش ِ واگرد   
toš-e vâgard

Fr.: choc en retour   

A → shock front in a → supernova remnant (SNR) arising from the interaction of the → supersonic  → forward shock wave with the → interstellar medium (ISM) material. The reverse shock forms as the high pressure gas behind the forward shock wave expands and pushes back on the stellar ejecta. Reverse shock propagates into ejecta, starting from outside.

reverse; → shock.

  تش، شوک   
toš, šok

Fr.: choc   

A sharp change in the properties of a gas (density, pressure, temperature).

Shock "sudden blow," from M.Fr. choc "violent attack," from O.Fr. choquer "to strike against, clash;" cf. Du. schokken "to shake, jolt, jerk."

Toš, from Tabari toš "violent blow," batoštən "to strike suddenly," Kurd. tuš "collision," maybe related to Pers. tuš "strength, vigor;" Av. təviši- "strength," tavah- "power;" O.Pers. tauman- "power, strength," tunuvant- "powerful," from tav- "to have power, to be strong, to be able" (related to tavân "power, strength," tavânestan "to be powerful, able;" variants tâv, tâb "power"); cf. Skt. tu- "to be strong, to have authority," tavas-, tavisa- "strong, energetic," tavisi- "power, strength."
Šok, loan from Fr., as above.

shock breakout
  برونزنی ِ شوک، ~ تش   
borunzani-ye šok, ~ toš

Fr.: émergence de l'onde de choc   

A burst of very bright → ultraviolet or → soft X-ray radiation expected to occur in → core-collapse supernovae at the instant when the → supernova shock breaks out of the stellar surface. During the collapse of the progenitor → massive star, the density in the iron core increases drastically. Once the core material reaches → nuclear density, the core rebounds generating a → shock wave that moves outward through the star. When the shock reaches the outermost layers, it ejects them out into space at → relativistic speeds.

shock; breakout "a forceful escape from being confined or restrained," from break, from M.E. breken, O.E. brecan (cf. Du. breken, O.H.G. brehhan, Ger. brechen), from PIE base *bhreg- "to break" (see also → fraction) + → out.

Borunzani "emergence, evasion," from borun, → out, + zani verbal noun of zadan "to strike, beat," from Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *gwhen- "to strike, kill."

shock diamond
  الماس ِتش   
almâs-e toš

Fr.: diamant de choc   

Any of a series of rings/disks that are formed in a jet flow exhausting a → nozzle when there is a huge difference between the exit pressure and the ambient pressure. At sea level, the exhaust pressure might be lower than the thick atmosphere. In contrast, at very high altitudes, the exhaust pressure might be higher than the thin atmosphere. Shock diamonds can appear just as a rocket is taking off, or at high altitudes when it shifts into → supersonic speed. Shock diamonds are also known as Mach diamonds, → Mach disks, Mach rings, doughnut tails, or thrust diamonds.

shock; → diamond.

shock front
  پیشان ِ تش، ~ شوک   
pišân-e toš, ~ šok

Fr.: front de choc   

The boundary over which the physical conditions undergo an abrupt change because of a → shock wave.

shock; → front.

shock wave
  موج ِ تش، ~ شوک   
mowj-e toš, ~ šok

Fr.: onde de choc   

A narrow region of abrupt, nearly discontinuous change in the physical characteristics of a medium in which the flow of a fluid changes from subsonic to supersonic. Across a shock wave there is always an extremely rapid rise in pressure, temperature, and density of the fluid.

shock; → wave.

shocked quartz
  کو‌آرتز ِ تشیده، ~ شوکیده   
kuârtz-e tošidé, ~ šokidé

Fr.: quartz choqué   

A form of quartz that has a deformed microscopic structure caused by intense pressure which alters the crystalline structure of quartz along planes inside the crystal. It was first discovered after underground nuclear bomb testing. It is found worldwide at the boundary between Cretaceous and Tertiary rocks. This is further evidence (in addition to iridium enrichment) that the transition between the two geological eras was caused by a large meteorite impact.

shock; → impact.

supernova shock
  شوک ِ ابر-نوختر، تش ِ ~   
šok de abar-now-axtar, toš-e ~

Fr.: choc de supernova   

A → shock wave that forms when the inner → iron core (of ~ 0.5 Msun) → collapses until it reaches densities in excess of → nuclear density. At this point the pressure rises dramatically and resists further collapse. The homologous core bounces and drives out a shock wave that works its way through the remainder of the initial iron core. The small compressibility of nuclear matter halts the infall of the innermost core by an elastic collective bounce whose kinetic energy is almost immediately depleted by the → photodisintegration of heavy nuclei and the emission of → neutrinos.

supernova; → shock.

termination shock
  تش ِ پایانی، شوک ِ ~   
toš-e pâyâni, šok-e ~

Fr.: choc terminal   

A → shock wave inside the → heliopause where the → supersonic → solar wind abruptly slows from an average speed of 500 km s-1 to → subsonic and becomes denser and hotter.

Termination, verbal noun from terminate, from → term; → shock.

Toš, šok, → shock; pâyâni, → terminal.

thermal shock
  تش ِ گرمایی، شوک ِ ~   
toš-e garmâyi, šok-e ~

Fr.: choc thermique   

Stresses induced in a material because of rapid temperature change or a → thermal gradient .

thermal; → shock.