An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Of or pertaining to Sir Isaac Newton or to his theories or discoveries.

Newtonian, from → Newton + -ian a suffix forming adjectives.

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.

Same as the → gravitational constant.

→ Newtonian; → constant; → gravitation.

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.

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

→ Newtonian; → fluid.

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

→ Newtonian; → focus.

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.

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

→ Newtonian; → mechanics.

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

→ Newtonian; → potential.

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.

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.

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.

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."

Podâ, literally "placed after," from *upada-, from *upa- "near, next, after," + *dâ- "to place, put," → thesis; cf. Baluci pôši "the day after tomorrow," from pô- contraction of *upa- + *aušah- "dawn," + → aurora, + suffix -i; cf. also Baluci godâ (from *uidâ-?) "then, next;" Bašâgardi, Baluci randâ "next, then."

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.

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.

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 10⁷→ solar 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.

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.

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.

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

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.