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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 464
local position invariance
  ناورتایی ِ نهش ِ محلی   
nâvartâyi-ye neheš-e mahali

Fr.: invariance de position locale   

Einstein equivalence principle.

local; → position; → invariance.

local sidereal time
  زمان ِ اختری ِ محلی   
zamân-e axtari-ye mahali

Fr.: temps sidéral local   

Local time measured by the apparent motion of the stars. It is the most useful form of sidereal time since it gives the right ascension of a transiting celestial object at a given location.

local; → sidereal; → time.

Local Spur
  شخاک ِ محلی   
šaxâk-e mahali

Fr.: bras local   

Same as → Orion Arm.

local; → → spur.

local standard of rest
  استانده‌ی ِ محلی ِ آرم   
estânde-ye mahali-ye âram

Fr.: standard local de repos   

A frame of reference that turns around the Galactic center at a velocity and a distance which are the mean values for the stars in the solar neighborhood. In this reference system the stars belonging to the solar neighborhood are statistically at rest. The orbital velocity of the Local Standard of Rest around the Galaxy is about 220 km/sec.

local; → standard; → rest.

Local Supercluster
  ا َبَرخوشه‌ی ِ محلی   
abarxuše-ye mahali (#)

Fr.: superamas local   

The supercluster to which the Local Group belongs. It is composed of some 100 clusters of galaxies, with the Virgo cluster of galaxies at its center.

local; → supercluster.

local thermodynamic equilibrium (LTE)
  ترازمندی ِ گرماتوانیک ِ محلی   
tarâzmandi-ye garmâtavânik-e mahali

Fr.: équilibre thermodynamique local   

The assumption that all distribution functions characterizing the material and its interaction with the radiation field at a point in the star are given by → thermodynamic equilibrium relations at local values of the temperature and density.

local; → thermodynamic; → equilibrium.

local time
  زمان ِ محلی   
zamân-e mahali (#)

Fr.: temps local   

Time based upon the local meridian as reference, in contrast to that of the time zone within which the place is located, or the Greenwich time.

local; → time.

local Universe
  گیتی ِ محلی   
giti-ye mahali

Fr.: Univers local   

A not well-defined concept describing a region of radius within ~ 20 → Mpc centered on the → Local Group of galaxies, corresponding to → redshift z ≤ 0.01. See also the → Local Volume.

local; → Universe.

Local Volume (LV)
  گنج ِ محلی   
gonj-e mahali

Fr.: Volume local   

A sphere of radius ~ 10 Mpc centered on the → Local Group of galaxies. The Local Volume includes at least 500 known galaxies, many of which congregate in well-known groups like the Local Group, the relatively loose → Sculptor Group, and the more compact Centaurus A group. As of 2010, the latest catalog of LV galaxies was presented by Karachentsev et al. (2004, AJ 127, 2031). About 85% of the LV population are → dwarf galaxies which contribute to about 4% to the local optical luminosity density and roughly to 10-15% to the total H I mass density.

local; → volume.

localization
  محل‌گیری   
mahal giri (#)

Fr.: localisation   

The condition of the wave-function of an electron if it is confined to a small region of a large system rather than being extended through the system.

Verbal noun of → localize.

localize
  ۱) محل‌دادن؛ ۲) محل‌گرفتن   
1) mahal dâdan; 2) mahal gereftan

Fr.: 1) localise; 2) se localiser   

1) To confine, restrict, or attribute to a particular locality.
2) To become local, especially to become fixed in one area or part.

From → local + → -ize

lock
  ۱) قفل؛ ۲) قفل کردن، ~ شدن   
1) qofl (#); 2) qofl kardan, ~ šodan

Fr.: 1) vérouille; 2) vérouiller, se vérouiller   

1) A device fitted to a gate, door, drawer, lid, etc, to keep it firmly closed and often to prevent access by unauthorized persons.
2) To fasten (a door, gate, etc) or (of a door, etc) to become fastened with a lock, bolt, etc, so as to prevent entry or exit (Dictionary.com).

M.E., from O.E. loc "fastening, bar;" cognate with M.L.G. lok, O.H.G. loh "dungeon," Ger. Loch "opening, hole," O.N. lok "a cover, lid;" akin to O.E. lucan "to shut."

Qofl, loan from Ar.

Lockman hole
  سوراخ ِ لاکمن   
surâx-e Lockman

Fr.: trou de Lockman   

A region in the sky lying roughly between the → pointer stars of the → Big Dipper that is almost free from → neutral hydrogen gas in the → Galaxy. It is centered at R.A. 10h 45m, Dec. +57° 20', has an area of 15 square degrees, and a → column density of NH I ≤ 5 x 1018 cm-2. The Lockman hole is one of the favorite directions for obtaining a clear and unobstructed view of objects in deep space, far beyond our own Galaxy.

Named after Felix J. Lockman et al., 1986, ApJ 302, 432; → hole.

locus
  محلگان   
mahalgân

Fr.: lieu géométrique   

The aggregate of all possible positions of a moving or generating element, e.g. the locus of points equidistant from a given point is a circle whose center is the given point.

From L. locus "place," from Old L. stlocus, literally "where something is placed," from PIE base *st(h)el- "to cause to stand, to place."

Mahalgân, from mahal "place, locality" + -gân relation and multiplicity suffix.

lodranite
  لودرانیت   
lodrânit

Fr.: lodranite   

A rare type of → achondritemeteorite.

Named after Lodhran (Punjab), Pakistan, where the type specimen fell on 1 October 1868.

LOFAR
     
LOFAR

Fr.: LOFAR   

A low frequency radio telescope network concentrated in the Netherlands with extensions into other European countries. It consists of a core and an extended → array in the Netherlands as well as in surrounding European countries with maximum → baselines of 2 km, 100 km, and 1,000 km respectively. LOFAR will be the largest radio telescope ever built, using a new concept based on a vast array of simple omni-directional antennas. The array will operate at the lowest frequencies that can be observed from Earth, at 30-250 MHz. About 75% of the construction is finished and LOFAR has already started its → commissioning period. When entirely finished, it will consist of 45,000 small antennas, distributed within 48 stations in the north east of the Netherlands, nearby parts of Germany, the UK, France, Sweden, and perhaps later Poland and Spain. The extensions in the United Kingdom, Germany, and France are completed. The French extension, located in the Nançay station of Paris Observatory (190 km south of Paris), is fully operational since December 2010. Moreover, a project to extend the low-frequency component of the Nançay station is under study. LOFAR is a forerunner of the future → Square Kilometer Array (SKA) project. See also the LOFAR homepage.

LOFAR, short for → LOw; → Frequency; → ARray.

logarithm
  لگاریتم   
logâritm (#)

Fr.: logarithme   

The → exponent of the → power to which it is necessary to raise a fixed number to produce the given number. The fixed number is called the → base. The logarithm of x to the base a, denoted loga(x), is the unique → real number  y such that ay = x. In the familiar system of → common logarithms, the base is 10. In the system of → natural logarithms, the base is e = 2.7182818 ... (→ number e). For example, the logarithm of 100 (base 10) is 2 because 102 = 100.

Mod.L. logarithmus, coined by Scottish mathematician John Napier (1550-1617), literally "ratio-number," from Gk. logos "proportion, ratio, word," → logic + arithmos "number," → arithmetic.

logarithmic
  لگاریتمی   
logâritmi (#)

Fr.: logarithmique   

Of or pertaining to a → logarithm.

logarithm; → -ic.

logarithmic extinction
  خاموشی ِ لگاریتمی   
xâmuši-ye logâritmi

Fr.: extinction logarithmique   

Same as → reddening coefficient.

logarithmic; → extinction.

logarithmic scale
  مرپل ِ لگاریتمی   
marpel-e logâritmi

Fr.: échelle logarithmique   

A scale of measurement in which an increase of one unit represents a tenfold increase in the quantity measured (for common logarithms)

logarithmic; → scale.

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