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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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lunar far side
  روی ِ دور ِ مانگ   
ruy-e dur-e mâng

Fr.: face cachée de la Lune   

The Moon's hemisphere which is not visible from the Earth. The Moon always shows the same face to the Earth, because Earth and Moon are → tidally locked. This means that the period of → lunar rotation on it axis is the same as its sidereal revolution period around the Earth (→ sidereal month). In other words, the Moon is in → synchronous rotation with the Earth. As a result, the same side always faces the Earth. To be more precise, taking the lunar → libration into account, the Moon presents about 59% of its surface to Earth. → libration in longitude, → libration in latitude, → physical libration, → geometrical libration.

lunar; → far; → side.

lunar formation
  دیسش ِ مانگ   
diseš-e Mâng

Fr.: formation de la Lune   

See → Moon formation.

lunar; → formation.

lunar geology
  زمین‌شناسی ِ ماه   
zaminšenâsi-ye mâh

Fr.: géologie lunaire   

The study of the → Moon's → crust, → rocks, strata (→ stratum), etc.

lunar; → geology.

lunar highland
  کوهسار ِ مانگی   
kuhsâr-e mângi

Fr.: hauts plateaux lunaires   

A light color area on the → Moon, as contrasted with → lunar maria. Also called terra.

lunar; → highland.

lunar horizon glow
  فروغ ِ افق ِ ماه   
foruq-e ofoq-e mâh

Fr.: éclat de l'horizon lunaire   

A very bright crescent of light glowing on the lunar horizon at → sunset or just before → sunrise. It has been suggested that → lunar dust is transported electrically high into sky, allowing sunlight to scatter and create glows. On the day side of the → Moon, solar → ultraviolet radiation is strong enough to kick → electrons from → dust grains in the lunar soil. Removal of electrons, which have a negative electric charge, leaves the dust with a positive electric charge. Since like charges repel, the positively charged dust particles get pushed away from each other, and the only direction not blocked by more dust is up. In the 1960s, Surveyor probes filmed a glowing cloud floating just above the lunar surface during sunrise. Later, Apollo 17 astronaut Gene Cernan, while orbiting the Moon, recorded a similar phenomenon at the sharp line where lunar day meets night, called the → terminator.

lunar; → horizon; → glow.

lunar mansion
  منزل ِ ماه   
manzel-e mâh (#)

Fr.: maison lunaire   

One of the 28 divisions of the sky, identified by the prominent stars in them, that the Moon passes through during its monthly cycle, as used in ancient Chinese, Hindu, and Arab astronomy/astrology.

From O.Fr. mansion, from L. mansionem (nom. mansio) "a staying, a remaining, night quarters, station," from manere "to stay, abide" (Fr. maison, ménage; E. manor, mansion, permanent); cf. Pers. mân "house, home," mândan "to remain, stay, relinquish, leave;" Mid.Pers. mândan "to remain, stay;" O.Pers. mān- "to remain, dwell;" Av. man- "to remain, dwell; to wait;" Gk. menein "to remain;" PIE base *men- "to remain, wait for."

Manzel, from Ar. "dwelling, habitation, mansion."

lunar mare
   "دریای ِ ماه"   
"daryâ-ye mâh" (#)

Fr.: mer lunaire   

An area on the surface of the → Moon that appears darker and smoother than its surroundings. Once thought to be seas, lunar maria are now known to be basaltic basins created by volcanic → lava floods; plural maria.

lunar; L. mare "sea," plural form maria, because Galileo thought the dark featureless areas on the Moon were → seas.

lunar maria
   "دریاهای ِ ماه"   
"daryâhâ-ye mâh" (#)

Fr.: mer lunaire   

Plural of → lunar mare.

lunar mare.

lunar mass
  جرم ِ ماه، ~ مانگ   
jerm-e mâh (#), ~ mâng

Fr.: masse lunaire, masse de la Lune   

The mass of the → Moon, which is 7.35 x 1022 kg, about 1/81 of the Earth's mass.

lunar; → mass.

lunar month
  ماه ِ مانگی   
mâh-e mângi

Fr.: mois lunaire   

The average time between successive new or full moons. Also called → synodic month, → lunation.

lunar; → month.

lunar node
  گره، گوزهر   
gereh (#), gowzahr (#)

Fr.: nœud   

One of the two points of intersection of the orbit of the Moon with the plane of → ecliptic. Indeed, the lunar orbit is tilted by about 5 degrees relative to the ecliptic. The revolution period of a lunar node in ecliptic is 18.61 years. Due to perturbation by the Sun, the lunar nodes slowly regress westward by 19.3° per year. See also → ascending node; → descending node.

lunar; → node.

Gereh, → node; gowzahri, related to gowzahr, → draconic month.

lunar orbit node
  گره ِ مداری ِ ماه   
gereh-e madâri-ye mâh

Fr.: nœud de l'orbite lunaire   

Same as → lunar node.

lunar; → orbit; → node.

lunar parallax
  دیدگشت ِ مانگی   
didgašt-e mângi

Fr.: parallaxe lunaire   

The apparent shift in the → Moon's position relative to the background stars when observed from different places on Earth. The first parallax determination was for the Moon, by Hipparchus (150 B.C.). He determined that one-fifth of the Sun's angular diameter corresponded to the lunar parallax between Hellespont and Alexandria.

lunar; → parallax.

lunar phase
  سیمای ِ مانگ   
simâ-ye mâng

Fr.: phase de la lune   

One of the various changes in the apparent shape of the Moon, because as the Moon orbits the Earth different amounts of its illuminated part are facing us. The phases of the Moon include: the → new moon, → waxing crescent, → first quarter, → waxing gibbous, → full moon, → waning gibbous, → last quarter, → waning crescent, and → new moon again.

lunar; → phase.

lunar probe
  گمانه‌ی ِ مانگی   
gomâne-ye mângi

Fr.: sonde lunaire   

A probe for exploring and reporting on conditions on or about the Moon.

lunar; → probe.

lunar recession
  دورشد ِ ماه   
duršd-e mâh

Fr.: éloignement de la lune   

The process whereby the → Moon gradually moves out into a slightly larger orbit. The → gravitational attraction of the Moon on the → Earth creates two ocean → tidal bulges on the opposite sides of our planet. The Earth rotates faster than the Moon revolves about the Earth. Therefore, the tidal bulge facing the Moon advances the Moon with respect to the line joining the centers of the Earth and the Moon. The Moon's gravity pulls on the bulge and slows down the → Earth's rotation. As a result, the Earth loses → angular momentum and the days on Earth are gradually increasing by 2.3 milliseconds per century. Since the angular momentum in the → Earth-Moon system is conserved, the Earth must impart the loss in its own angular momentum to the Moon's orbit. Hence, the Moon is being forced into a slightly larger orbit which means it is receding from the Earth. However, eventually this process will come to an end. This is because the Earth's own rotation rate will match the Moon's orbital rate, and it will therefore no longer impart any angular momentum to it. In this case, the planet and the Moon are said to be tidally locked (→ tidal locking). This is a stable situation because it minimises the energy loss due to friction of the system. Long ago, the Moon's own rotation became equal to its orbital period about the Earth and so we only see one side of the Moon. This is known as → synchronous rotation and it is quite common in the solar system. The Moon's average distance from Earth in increasing by 3.8 cm per year. Such a precise value is possible due to the Apollo laser reflectors which the astronauts left behind during the lunar landing missions (Apollo 11, 14, and 15). Eventually, the Moon's distance will increase so much that it will be to far away to produce total eclipses of the Sun.

lunar; → recession.

lunar regolith
  سنگپوش ِ ماه، ~ مانگی   
sangpuš-e mâh, ~ mângi

Fr.: régolithe lunaire   

The loose, fragmentary material on the Moon's surface. The lunar regolith has resulted from → meteorite collisions all along the Moon's history. It is the → debris thrown out of the → impact craters. The composition of the lunar regolith varies from place to place depending on the rock types impacted. Generally, the older the surface, the thicker the regolith. Regolith on young → maria may be only 2 meters thick; whereas, it is perhaps 20 meters thick in the older → highlands.

lunar; → regolith.

lunar rotation
  چرخش ِ مانگ   
carxeš-e mâng

Fr.: rotation de la Lune   

The Moon's motion around its axis, which takes place in 27.321 661 days (→ sidereal month). Since the Moon and the Earth are → tidally locked our satellite has a → synchronous rotation. This means that it rotates once on its axis in the same length of time it takes to revolve around Earth. That is why the Moon always shows the same face to us. However, over time we can see up to 59 percent of the lunar surface because the Moon does not orbit at a constant speed (→ libration in longitude) and its axis is not perpendicular to its orbit (→ libration in latitude). The Moon also creates tides in Earth oceans. As the Earth rotates, the rising and falling sea waters bring about friction within the liquid itself and between the water and solid Earth. This removes energy from Earth's rotation and causes it to spin more slowly. As a result, days are getting longer, at about 2 milliseconds per century. On the other hand, since the → angular momentum of the → Earth-Moon system must be conserved, the Moon gradually moves away from the Earth. This, in turn, requires its orbital period to increase and, because the Moon is tidally locked to Earth, to spin more slowly.

lunar; → rotation.

lunar sidereal orbital period
  دوره‌ی ِ مداری ِ اختری ِ مانگ   
dowre-ye madâri-ye axtari-ye mâng

Fr.: période orbitale sidérale de la Lune   

Same as → sidereal month.

lunar; → sidereal; → orbital; → period.

lunar terra
   "خشکی ِ ماه"   
"xoški-ye mâh"

Fr.: terre   

lunar highland.

lunar; terra "earth," → terrestrial.

<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl ura uti val var vec vel ver Ver vie vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>