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

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Number of Results: 13176 Search : in
harmonic oscillator
  نَو ِشگر ِ هماهنگ   
navešgar-e hamâhang (#)

Fr.: oscillateur harmonique   

Any oscillating particle in harmonic motion.

harmonic; → oscillator.

harmonic progression
  فرایازی ِ هماهنگ   
farâyâzi-ye hamâhang

Fr.: progression harmonique   

Math.: Any ordered set of numbers, the reciprocals of which have a constant difference between them. For example 1, ½, 1/3, ¼, ..., 1/n. Also called → harmonic sequence.

harmonic; progression.

harmonic sequence
  پی‌آیه‌ی ِ هماهنگ   
peyâye-ye hamâhang

Fr.: suite harmonique   

harmonic progression.

harmonic; → sequence.

harmonic series
  سری ِ هماهنگ   
seri-ye hamâhang

Fr.: série harmonique   

Overtones whose frequencies are integral multiples of the → fundamental frequency. The fundamental frequency is the first harmonic.

harmonic; → series.

Haro galaxy
  کهکشان ِ هارو   
kahkešân-e Hâro (#)

Fr.: galaxie de Haro   

A type of galaxies characterized by strong emission in the blue and violet regions of the spectrum. They are often elliptical or lenticular.

Named after the Mexican astronomer Guillermo Haro (1913-1988), who first compiled a sample of these objects; → galaxy.

HARPSpol
     
HARPSpol

Fr.: HARPSpol   

A → polarimeter using the → spectrographic capabilities of the → High Accuracy Radial velocity Planet Searcher (HARPS) to measure the → Zeeman effect indicating the presence of a → magnetic field at the surface some stars. This combined instrument is installed at the ESO 3.6-m telescope at → La Silla Observatory (Chile) and covers the 3800-6900 Å wavelength region with an average → spectral resolution of 110,000 (Piskunov, et al., 2011, ESO Messenger 143, 7). HARPSpol is mainly used in research on → magnetic fields in stars. See also → magnetic star, → magnetic massive star, → magneto-asteroseismology

HARPS + -pol, from → polarimeter.

Harshad number
  عدد ِ هرشد   
adad-e Harshad

Fr.: nombre Harshad   

A number that is divisible by the sum of its digits. For example, 18 is a Harshad number because 1 + 8 = 9 and 18 is divisible by 9 (18/9 = 2). The simplest Harshad numbers are the two-digit Harshad numbers: 10, 12, 18, 20, 21, 24, 27, 30, 36, 40, 42, 45, 48, 50, 54, 60, 63, 70, 72, 80, 81, 84, 90. They are sometimes called Niven numbers.

The name Harshad was given by Indian mathematician Dattaraya Kaprekar (1905-1986) who first studied these numbers. Harshad means "joy giver" in Sanskrit, from harṣa- "joy" and da "to give," → datum.

Hartle-Hawking initial state
  استات ِ آغازین ِ هارتل-هاؤکینگ   
estât-e âqâzin-e Hartle-Hawking

Fr.: état initial de Hartle-Hawking   

A proposal regarding the initial state of the → Universe prior to the → Planck era. This → no boundary hypothesis assumes an imaginary time in that epoch. In other words, there was no real time before the → Big Bang, and the Universe did not have a beginning. Moreover, this model treats the Universe like a quantum particle, in an attempt to encompass → quantum mechanics and → general relativity; and attributes a → wave function to the Universe. The wave function has a large value for our own Universe, but small, non-zero values for an infinite number of other possible, parallel Universes.

Hartle, J., Hawking, S., 1983, "Wave function of the Universe," Physical Review D 28; → initial; → state.

Hartley band
  باند ِ هارتلی   
bând-e Hartley

Fr.: bande de Hartley   

A band in the → absorption spectrum of → ozone (O3) extending in the → ultraviolet from 200 nm to 300 nm. It is stronger than the → Huggins band. See also: → Hartley band.

W. N. Hartley, J. Chem. Soc. 39, 111 (1881).

Hartmann test
  آزمون ِ هارتمان   
âzmun-e Hârtman (#)

Fr.: test de Hartmann   

A way of testing the quality of optical systems. In this method, incident rays from a point source are isolated by small holes in an opaque screen located close to the lens or mirror under test. Photographic plates are inserted into the beam within and beyond the focal region. The black dots on the exposed plates, which reveal differences of optical focus in the various zones of the lens or mirror, are analyzed to yield the objective's figure. → Shack-Hartmann wavefront sensor.

Named after the German astronomer Johannes Hartmann (1865-1936), who developed the method. → test.

hartree
  هارتری   
hartree

Fr.: hartree   

A unit of energy used in atomic and molecular physics; symbol Ha or Eh. It is defined as: 1 Ha = mee4/(4ε02ħ), where me is the mass of electron, e its charge, ε0 the → permittivity of vacuum, and ħ → reduced Planck's constant. Its value is 2 → rydbergs, or 4.3597 x 10-18 → joule, or 27.213 → electron-volts.

Named for the British physicist and mathematician Douglas R. Hartree (1897-1958).

Harvard classification
  رده‌بندی ِ هاروارد   
radebandi-ye Hârvârd (#)

Fr.: classification de Harvard   

A classification of stellar spectra published in the Henry Draper catalogue, which was prepared in the early twentieth century by E. C. Pickering and Miss Annie Canon. It is based on the characteristic lines and bands of the chemical elements. The most important classes in order of decreasing temperatures are as follows: O, B, A, F, G, K, M.

Harvard, named for John Harvard (1607-1638), the English colonist, principal benefactor of Harvard College, now Harvard University. → classification

harvest
  ۱) خرمن؛ ۲) خرمن کردن، ~ برداشتن   
1) xarman; 2) xarman kardan, ~ bardâštan

Fr.: 1) moisson, récolte; 2) récolter   

1a) The gathering of a ripened → crop.
1b) (Agriculture) the crop itself or the yield from it in a single growing season.
2) To gather or reap (a ripened crop) from (the place where it has been growing) (TheFreeDictionary).

M.E. hervest, from O.E. hærfest "autumn;" cognate with Du. herfst, Ger. Herbst "autumn"); PIE *(s)kerp- "to gather, pluck, harvest," from *(s)ker- "to cut" (cf. Skt. krpāna- "sword, knife;" Gk. karpos "fruit;" L. carpere "to cut, divide, pluck;" Av. karət- "to cut," Mod.Pers. kârd "knife," as below).

Xarman, ultimately from *xramana-, from *xram- "to thresh;" cf. Ormuri šraməd, Parâci khamör, Yidgha xurom, xuräm; Nuristâni Kati kram- "to thresh;" Skt. kram- "to stride out, to go" (H. W. Bailey, 1979).

harvest moon
  ماه ِ خرمن‌برداری   
mâh-e xarman bardâri

Fr.: lune de moisson   

The → full moon that appears closest in time to the → autumnal equinox.

harvest; → moon.

hatch
  ۱) لاچیدن؛ ۲) لاچش؛ دریچه   
1) lâcidan; 2) lâceš; daricé

Fr.: 1) éclore; 2) éclosion; volet   

1) (of an egg) To open and produce a young animal; emerge from its egg.
2a) The act or process of hatching.
2b) A small opening in a wall that serves as a doorway or window. → dome hatch.

1) M.E. hachen "to produce young from eggs by incubation," probably from an unrecorded O.E *hæccan, of unknown origin, related to M.H.G., Ger. hecken "to mate" (used of birds).
2) M.E. hacche, O.E. hæcc "fence, half-gate;" cf. M.H.G. heck, Du. hek "gate, railing."

1) Lâcidan, from Tabari lâc "open, separated, wide aprat" (lâc hâytan "to split, to crack," lâc bazoən "to split, to tear"), may be from Proto-Ir. *rauj "to break, burst;" cf. Av. (+*fra-) fra.uruxti- "destruction;" Khotanese *rrus- "to burst, break;" Baluchi ruj- "to break open;" Bartangi, Oroshori ruj-/ruxt- "to dig;" Skt. roj- "to break, break open;" Pali luki- "part;" L. lugere "to mourn, grieve;" Armenian lucanem "I break up."
2) Daricé, from dar, → door, + -cé diminutive suffix.

Hatsya
  هتسیا   
Hatsya

Fr.: Hatsya   

The → component Aa of the → multiple star system  → Iota Orionis,. The name was approved in 2016 by the IAU Working Group on Star Names (WGSN).

Hatsya, of unknown origin.

Haumea
  هاؤمءا   
Haumea

Fr.: Hauméa   

A → dwarf planet located beyond → Neptune's orbit (→ trans-Neptunian object). Haumea is roughly the same size as → Pluto. It spins on its axis once every four hours, making it the fastest spinning known large object in the → solar system. It has two known moons, called Hi'aka and Namaka. Observations from multiple Earth-based observatories of Haumea passing in front of a distant star indicate the presence of a ring with a width of 70 km and radius of about 2,287 km. The ring is coplanar with both Haumea's equator and the orbit of its satellite Hi'aka. The → occultation by the main body indicates an oblong shape for Haumea with axes of about 2,322 × 1,701 × 1,138 km. In other words, along one direction, Haumea is significantly longer than → Pluto, while in another direction it has an extent very similar to Pluto, while in the third direction is much smaller. Haumea's orbit sometimes brings it closer to the Sun than Pluto, but usually Haumea is further (Ortiz et al., 2017, Nature 550, 219, doi:10.1038/nature24051).

Named for the Hawaiian goddess of childbirth and fertility (temporary designation 2003 EL61). Its moons are named for daughters of Haumea.

Hawking radiation
  تابش ِ هاؤکینگ   
tâbeš-e Hawking (#)

Fr.: rayonnement de Hawking   

The radiation produced by a → black hole when → quantum mechanical effects are taken into account. According to quantum physics, large fluctuations in the → vacuum energy occurs for brief moments of time. Thereby virtual particle-antiparticle pairs are created from vacuum and annihilated. If → pair production happens just outside the → event horizon of a black hole, as soon as these particles are formed they would both experience drastically different → gravitational attractions due to the sharp gradient of force close to the black hole. One particle will accelerate toward the black hole and its partner will escape into space. The black hole used some of its → gravitational energy to produce these two particles, so it loses some of its mass if a particle escapes. This gradual loss of mass over time means the black hole eventually evaporates out of existence. See also → Bekenstein formula, → Hawking temperature.

Named after the British physicist Stephen Hawking (1942-2018), who provided the theoretical argument for the existence of the radiation in 1974; → radiation.

Hawking temperature
  دمای ِ هاؤکینگ   
damâ-ye Hawking

Fr.: température de Hawking   

The temperature inferred for a → black hole based on the → Hawking radiation. For a → Schwarzschild black hole, one has TH = ħc3/(8πGMk) where ħ is the → reduced Planck's constant, c is the → speed of light, G is the → gravitational constant, M is the mass, and k is → Boltzmann's constant. The formula can approximately be written as: TH≅ 6.2 x 10-8 (Msun/M) K. Thus radiation from a solar mass black hole would be exceedingly cold, about 5 x 107 times colder than the → cosmic microwave background. Larger black holes would be colder still. Moreover, smaller black holes would have higher temperatures. A → mini black hole of mass about 1015 g would have TH≅ 1011 K.

Hawking radiation; → temperature.

Hayabusa2
  هایابوسا۲   
Hayabusa2

Fr.: Hayabusa2   

A Japanese → asteroid sampling mission devoted to the study of → Ryugu. It was launched on December 3, 2014 and successfully arrived at the asteroid on June 27, 2018. The Hayabusa2 mission includes four rovers with various scientific instruments. On September 21, 2018 the first two of these rovers, MINERVA-II robots, which hop around the surface of the asteroid, were released from Hayabusa2. This marked the first time a mission has completed a successful landing on a fast-moving asteroid body. This was followed later by the deployment of MASCOT (Mobile Asteroid Surface Scout), a lander developed by the German space agency DLR in partnership with the French Center for Spatial Studies (CNES). It carried four instruments and with its 16 h lifetime battery collected data on the surface structure and mineralogical composition, the thermal behaviour and the magnetic properties of the asteroid. Hayabusa2 is expected to leave Ryugu with the collected samples in late 2019 and return to Earth in 2020.

Hayabusa "peregrine falcon" in Japanese.

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