An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < -ne nan nat nea neg Ner neu new New ni- nod non non non Nor noz nuc nul num > >>

Number of Results: 375
Newtonian approximation
  نزدینش ِ نیوتنی   
nazdineš-e Newtoni

Fr.: approximation newtonienne   

A particular solution of the → general relativity when the → gravitational mass is small. The → space-time is then approximated to the → Minkowski's and this leads to → Newtonian mechanics.

Newtonian; → approximation.

Newtonian constant of gravitation
  پایای ِ گرانش ِ نیوتن   
pâyâ-ye gerâneš-e Newton

Fr.: constante de la gravitation newtonienne   

Same as the → gravitational constant.

Newtonian; → constant; → gravitation.

Newtonian cosmology
  کیهان‌شناسی ِ نیوتنی   
keyhânšenâsi-ye Newtoni

Fr.: cosmologie newtonienne   

The use of → Newtonian mechanics to derive homogeneous and isotropic solutions of → Einstein's field equations, which represent models of expanding Universe. The Newtonian cosmology deviates from the prediction of → general relativity in the general case of anisotropic and inhomogeneous models.

Newtonian; → cosmology.

Newtonian fluid
  شاره‌ی ِ نیوتنی   
šârre-ye Newtoni

Fr.: fluide newtonien   

Any → fluid with a constant → viscosity at a given temperature regardless of the rate of → shear.

Newtonian; → fluid.

Newtonian focus
  کانون ِ نیوتن، ~ نیوتنی   
kânun-e Newton, ~ Newtoni

Fr.: foyer de Newton   

The focus obtained by diverting the converging light beam of a reflecting telescope to the side of the tube.

Newtonian; → focus.

Newtonian limit
  حد ِ نیوتنی   
hadd-e Newtoni

Fr.: limite newtonienne   

The limit attained by → general relativity when velocities are very smaller than the → speed of light or gravitational fields are weak. This limit corresponds to the transition between general relativity and the → Newtonian mechanics. See also → Newtonian approximation.

Newtonian; → limit.

Newtonian mechanics
  مکانیک ِ نیوتنی   
mekânik-e Newtoni (#)

Fr.: mécanique newtonienne   

A system of mechanics based on → Newton's law of gravitation and its derivatives. Same as → classical mechanics.

Newtonian; → mechanics.

Newtonian potential
  توند ِ نیوتنی   
tavand-e Newtoni

Fr.: potentiel newtonien   

A potential in a field of force obeying the inverse-square law such as → gravitational potential.

Newtonian; → potential.

Newtonian principle of relativity
  پروز ِ بازانیگی ِ نیوتن   
parvaz-e bâzânigi-ye Newton

Fr.: principe de relativité de Newton   

The Newton's equations of motion, if they hold in any → reference frame, they are valid also in any other reference frame moving with uniform velocity relative to the first.

Newtonian; → principle; → relativity.

Newtonian relativity
  بازانیگی ِ نیوتنی   
bâzânigi-ye Newtoni

Fr.: relativité newtonienne   

The laws of physics are unchanged under → Galilean transformation. This implies that no mechanical experiment can detect any intrinsic diff between two → inertial frames. Same as → Galilean relativity.

Newton; → relativity.

Newtonian telescope
  دوربین ِ نیوتن، تلسکوپ ِ ~   
durbin-e Newton, teleskop-e ~

Fr.: télescope de Newton, ~ newtonien   

A telescope with a concave paraboloidal objective mirror and a small plane mirror that reflects rays from the primary mirror laterally outside the tube where the image is viewed with an eyepiece.

Newtonian; → telescope.

pasin (#)

Fr.: prochain   

Immediately following in time, order, place, and so on.

M.E., from O.E. next, nehst, niehsta, nyhsta "nearest, closest," superlative of neah "nigh" + superlative suffix. Cognate with Du. naast "next," O.H.G. nahisto "neighbor," Ger. nächst "next."

Pasin, from pas "after; behind;" → back-.

NGC 1275
NGC 1275

Fr.: NGC 1275   

A → Seyfert galaxy, which is the central, dominant member of the large and relatively nearby → Perseus cluster of galaxies. A powerful source of X-rays and radio emission, NGC 1275 accretes matter (→ accretion) as intercluster material falls into it, ultimately feeding a → supermassive black hole (SMBH) at the galaxy's core. NGC 1275, hosts a narrow-line radio source, Perseus A (3C 84), which interacts with the intracluster gas through its jets and bipolar outflows.

NGC, → New General Catalogue.

NGC 346
NGC 346

Fr.: NGC 346   

A prominent → star cluster, and the ionizing core of giant → H II region → N66 in the → Small Magellanic Cloud galaxy. NGC 346 hosts the largest sample of young, → massive stars in the whole SMC, containing 33 → O-type stars among which 11 are of type O6.5 or earlier. This is young massive star cluster with an estimated age of about 3 million years.

346, a serial number in the → New General Catalogue.

NGC 3603
NGC 3603

Fr.: NGC 3603   

The most massive and luminous visible → starburst region in the Galaxy. This is our local → giant H II region lying at a distance of about 6-7 kpc in the → Carina arm (→ right ascension = 11h, → declination = -61°). Its central starburst cluster hosts the largest known concentration of extremely young, mostly unevolved → high-mass stars in the Galaxy. With an age of only 1-2 Myr for its most massive stars, NGC 3603 is one of the youngest starburst clusters known. It has about 40 known → O stars and → W-R stars, producing a → Lyman continuum flux of 1051 s-1, about 100 times the ionizing power of the Orion → Trapezium cluster. The OB stars contribute to more than 2000 → solar masses to the cluster mass. With a bolometric luminosity over 107solar luminosities, NGC 3603 has about 10% of the luminosity of → 30 Doradus and looks in many respects very similar to its core, → R136. A total mass of 7,000 solar masses is measured in the inner 1 pc from the cluster center, whereas the → low-mass stars extend out to at least 5 pc. The mass segregated core of the cluster, with 105 solar masses per pc3, displays the highest local stellar density outside the Galactic Center region. The spectral analysis of the W-R like massive component in the cluster core (→ HD 97950) suggests a → metallicity close or equal to solar (See, e.g., Melena et al. 2008, AJ 135, 878, and references therein).

3603, a serial number in the → New General Catalogue.

NGC 3603-A1
NGC 3603-A1

Fr.: NGC 3603-A1   

A → binary star lying in the core of the Galactic → giant H II region  → NGC 3603. NGC 3603-A1 is double-eclipsing → Wolf-Rayet binary of type → WN6ha with an orbital period of 3.77 days. Their masses have been derived to be M1 = (116 ± 31) Msun for the primary and M2 = (89 ± 16) Msun for the secondary component of A1. The primary in A1 is the most massive star weighed so far (Schnurr et al., 2008, MNRAS 389, L38).

NGC 3603.

NGC 404
NGC 404

Fr.: NGC 404   

A galaxy discovered in 1784 by William Herschel that happens to lie nearly along the line of sight to the star → Beta Andromedae. More specifically, it lies at an angular separation of seven arc-minutes. For this reason it is known also as → Mirach's Ghost. NGC 404 is in fact a → dwarf galaxy lying at a distance of about 10 million → light-years (3.07 ± 0.37 Mpc). NGC 404 harbors a low-luminosity → active galactic nucleus powered by the lowest-mass (< 150,000 Msun) central → massive black hole (Nyland et al., 2017, ApJ 845, 50).

NGC, → New General Catalogue.

NGC 4993
NGC 4993

Fr.: NGC 4993   

A → lenticular galaxy (S0) in → Hydra constellation located about 130 million → light-years (40 ± 8 Mpc, → redshift z = 0.009680) from Earth, discovered by William Herschel in 1789. On 17 August 2017 the → Laser Interferometer Gravitational-Wave Observatory (LIGO) and the → Virgo Interferometer both detected → gravitational waves (→ GW170817) from the collision of two → neutron stars within this galaxy. The → electromagnetic counterpart GRB 170817A was detected 1.7 seconds later. The event was associated with a → kilonova offset 10.6 arcsec (corresponding to 2.0 kpc) to north-east from the nucleus of NGC 4993.

NGC, → New General Catalog

NGC 5866
NGC 5866

Fr.: NGC 5866   

A → lenticular galaxy in the constellation of the → Draco. It lies about 50 million → light-years (15.3 Mpc) distant and has a size of about 60,000 light-years. Due to its thin → rdge-on appearance, it is also called the → Spindle Galaxy. Known also as Messier 102.

5866, a serial number in the → New General Catalogue.

NGC 7023
NGC 7023

Fr.: NGC 7023   

A → reflection nebula located in the constellation → Cepheus at a distance of 1,300 → light-years. It was discovered by Sir William Herschel on October 18, 1794. The nebula, also known as the → Iris Nebula and → Caldwell 4, is about 6 light-years across. At the center of NGC 7023 lies an extremely young star named V380 Cep or SAO 19158 (mag. +7.1), which is associated with plenty of local dust. NGC 7023 is located 6 degrees northwest of the brightest star in Cepheus, Alderamin (α Cep - mag. +2.5) with third magnitude Alfirk (Beta Cephei) positioned about 3.5 degrees to the northeast. Only a degree east-northeast of NGC 7023 is Mira type variable star T Cep, which fluctuates between magnitudes +5.2 and +11.3 over a period of 388.14 days.

7023, a serial number in the → New General Catalogue.

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