An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 13116 Search : far
helio-
  هور-، خور-، خورشید-   
hur- (#), xor- (#), xoršid- (#)

Fr.: hélio-   

A combining form of Gk. helios "sun."

Helio-, combining form of from Gk. helios "sun;" cognate with Persian hur "sun", variant xor and xoršid (Av. hvarə-xšaēta- "shining sun"); Mid.Pers. xvar "sun;" Av. hû-, hvar- "sun;" Skt. surya-; L. sol; O.H.G. sunna; Ger. Sonne; E. sun; PIE *sawel- "sun."

heliocentric
  هورمرکزی، خورشیدمرکزی   
hurmarkazi (#), xoršid markazi (#)

Fr.: héliocentrique   

Having or representing the Sun as a center. → heliocentric cosmology, → heliocentric gravitational constant, → heliocentric Julian Day, → heliocentric parallax, → heliocentric system.

helio- + → center + → -ic.

heliocentric cosmology
  کیهان‌شناسی ِ هورمرکزی   
keyhânšenâsi-ye hurmarkazi (#)

Fr.: cosmologie héliocentrique   

A model of the Universe in which the Sun was centrally located.

heliocentric; → cosmology.

heliocentric gravitational constant
  پایای ِ گرانشی هورمرکزی   
pâyâ-ye gerâneši-ye hur-markazi

Fr.: constante gravitationnelle héliocentrique   

A parameter representing the product of the → gravitational constant by the → solar mass. It is 13.27 x 1019 m3 s-2.

heliocentric; → gravitational; → constant.

Heliocentric Julian Date
  گاهداد ِ ژولی‌ین ِ هورمرکزی   
gâhdâd-e žulian-e hurmarkazi

Fr.: date julienne héliocentrique   

The → Julian Date referenced to the center of the → Sun. Since the Earth revolves around the Sun, and since light travels at a finite speed, observations of a given object taken at different positions in the Earth's orbit are not equivalent, and so a correction for Earth's orbit around the Sun is required. Left uncorrected, the time of an observational event measured by Earth clocks will vary by 16.6 minute over the course of a year. If not properly accounted for, this can lead to a spurious signal in a → periodogram.

heliocentric; → Julian Date.

heliocentric parallax
  دیدگشت ِ هورمرکزی   
didgašt-e hurmarkazi

Fr.: parallaxe héliocentrique   

The parallax of a celestial body when viewed from two points in the Earth's orbit around the Sun. More specifically, the angular difference in a celestial object's position as seen from the center of the Sun and the center of the Earth. Also called → annual parallax.

heliocentric; → parallax.

heliocentric system
  راژمان ِ هورمرکزی   
râžmân-e hurmarkazi

Fr.: système héliocentrique   

A system in which the Sun is assumed to lie at its central point while the Earth and other bodies revolve around it.

heliocentric; → system.

heliogram
  هورنگاشت   
hurnegâšt (#)

Fr.: héliogramme   

A record made by a → heliograph.

helio-; + → -gram.

heliograph
  هورنگار   
hurnegâr (#)

Fr.: héliographe   

1) An instrument for photographing the Sun, consisting of a camera and a specially adapted telescope.
2) A simple device using a mirror to reflect sunlight to a distant observer. By moving the mirror, flashes of light can be used to send coded messages. The heliograph was a highly effective instrument for instantaneous optical communication over 80km or more in the 19th century.
3) Meteo.: An instrument which records the duration of sunshine and gives a quantitative measure of the amount of sunshine.

helio-; + → -graph.

heliometer
  هورسنج   
hursanj (#)

Fr.: héliomètre   

An instrument used to measure the angular separation of two stars that are too far apart to be included in the field of view of an ordinary telescope.  The instrument was originally designed for measuring the variation of the Sun's diameter at different seasons of the year.

helio- + → -meter.

heliopause
  هورمرز   
hurmarz

Fr.: héliopause   

The edge of the solar system where the pressure of the → solar wind balances that of the → interstellar medium plasma. In other words, the surface boundary that separates the → heliosphere from interstellar space. It is estimated to be situated 100 → astronomical units or more from the Sun. A → bow shock likely forms as the interstellar medium wind approaches the heliosphere and is deflected around the heliosphere, forcing it into a teardrop-shaped structure with a long, comet-like tail.

From → helio- + pause "break, cessation, stop," from M.Fr. pause, from L. pausa "a halt, stop, cessation," from Gk. pausis "stopping, ceasing," from pauein "to stop, to cause to cease."

Hurmarz, from hur, → helio-, + marz "frontier, border, boundary," → frontier.

helioseismology
  هورلرزه‌شناسی   
hurlarzešenâsi

Fr.: héliosismologie   

The branch of astrophysics that investigates the interior structure of the Sun by studying its surface wave oscillations. See also → asteroseismology and → stellar pulsation. The surface of the Sun vibrates much like a bell. A piano has 88 keys or musical tones, whereas the Sun has millions of notes. These vibrations are the result of internal pressure waves that reflect off the → photosphere and repeatedly cross the solar interior. They are detected through the → Doppler shift of absorption lines formed in the photosphere. Because these vibrations make the solar surface move up and down, analysis of the surface patterns is used to study conditions far below the Sun's surface. The mean period of the vibrations is about five minutes, which corresponds to a speed of 0.5 km s-1 or a frequency of about 3 mHz. See also → p mode.

From → helio- + → seismology.

heliosheath
  هورنیام   
hurniyâm

Fr.: héliogaine   

The region located between the → termination shock and the → heliopause where the turbulent and hot → solar wind is compressed as it passes outward against the interstellar wind.

Heliosheath, from → helio- + sheath, from O.E. sceað, scæð; cf. M.Du. schede, Du. schede, O.H.G. skaida, Ger. Scheide "scabbard."

Hurniyâm, from hur- "sun," → helio-, + niyâm "sheath," from Proto-Iranian *nigāma-, from ni- "down; into," → ni- (PIE), + gāma- "to go, to come" (Av. gam- "to come; to go," jamaiti "goes;" O.Pers. gam- "to come; to go;" Mod./Mid.Pers. gâm "step, pace," âmadan "to come;" cf. Skt. gamati "goes;" Gk. bainein "to go, walk, step;" L. venire "to come;" Tocharian A käm- "to come;" O.H.G. queman "to come;" E. come; PIE root *gwem- "to go, come"); cf. Skt. nigamá- "insertion, incorporation."

heliosphere
  هورسپهر   
hursepehr (#)

Fr.: héliosphère   

The vast, three-dimensional region of space around the Sun filled with the → solar wind and the remnant of the → solar magnetic field carried in it. It is bounded by the → heliopause, which is estimated to be 100 → astronomical units or more from the Sun. The radius of the heliosphere is expected to vary with the → solar cycle. The heliosphere may be very elongated owing to the presence of an interstellar wind of neutral hydrogen flowing from the direction of the Galactic center.

From → helio- + → sphere.

heliostat
  هورداشتار   
hurdâštâr

Fr.: héliostat   

An instrument consisting of a mirror moved by clockwork for tracking the movement of the Sun and reflecting the sunlight into a stationary solar telescope. A heliostat is similar to a → coelostat.

Heliostat, from → helio- + -stat prefix denoting something that stabilizes, keeps, fixes, from -stata, from Gk. -states "one that causes to stand," or statos "standing," from *sta- "to stand."

Hurdâštâr, from hur-, → helio- + dâštâr "holder, maintainer," from dâštan "to hold, maintain; to have; to possess;" Mid.Pers. dâštan; O.Pers./Av. dar- "to hold, keep back, maintain, keep in mind;" cf. Skt. dhr-, dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE base *dher- "to hold, support."

helium
  هلیوم   
helium (#)

Fr.: hélium   

Chemical element; symbol He; atomic number 2; atomic weight 4.0026; melting point below -272°C at 26 atmospheres pressure; boiling point -268.934°C at 1 atmosphere pressure.

Helium, from Gk. helios "sun;" cognate with Persian hur "sun", variant xor; Mid.Pers. xvar "sun;" Av. hû-, hvar- "sun;" Skt. surya-; L. sol; O.H.G. sunna; Ger. Sonne; E. sun; PIE *sawel- "sun." The element was discovered by spectroscopy during a solar eclipse in the Sun's chromosphere in 1868 by the French astronomer Pierre-Jules-Cesar Janssen (1824-1907).

helium abundance
  فراوانی ِ هلیوم   
farâvâni-ye heliom

Fr.: abondance de l'hélium   

The relative amount of helium with respect to another → chemical species, usually → hydrogen, in an astronomical object.

helium; → abundance.

helium burning
  سوزش ِ هلیوم   
suzeš-e heliyom

Fr.: combustion de l'hélium   

The stage in the evolution of a star, after the exhaustion of hydrogen, when the star produces its energy by the fusion of helium into carbon and oxygen.

helium; → burning.

helium flash
  درخش ِ هلیوم   
deraxš-e heliom (#)

Fr.: flash de l'hélium   

The sudden onset of → helium burning in the core of an → intermediate-mass star that has exhausted its hydrogen and has become a → red giant. With a → degenerate core, the temperature increases but the pressure does not. Therefore, the core cannot expand and cool, so the temperature continues to rise. When it approaches 100,000,000 K, helium will begin to fuse into carbon in the → triple alpha process. The helium flash ends the giant star's ascent of the → red giant branch. However, the violent ignition of helium in the core does not increase the star's luminosity. On the contrary, the energy released in the helium flash expands and cools the core and ultimately results in a reduction in the energy output. On the → H-R diagram the star moves down from red giant branch to the → horizontal branch, a stable state with steady helium burning in the core.

helium; → flash.

helium I
  هلیوم I   
heliom I

Fr.: hélium I   

1) The normal component of → liquid helium (4He) existing between the superfluid transition point (→ lambda point about 2.17 K) at 1 atmosphere of pressure and its boiling point of 4.2 K.
2) In stellar and interstellar plasma spectroscopy, neutral helium.

helium.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc 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 Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg 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 > >>