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

A sequence of → permitted transitions in the → ultraviolet from an → excited state (B) of the → molecular hydrogen (H₂) to the electronic → ground state, with ΔE > 11.2 eV, λ < 1108Å (first → band head). When a hydrogen molecule absorbs such a photon, it undergoes a transition from the ground electronic state to the excited state (B). The following rapid → decay creates an → absorption band in that wavelength range. See also → Werner band. → Lyman-Werner photon.

→ Lyman (Th. Lyman, 1906, Astrophys. J. 23, 181); → band.

A → dimensionless quantity used in → magnetohydrodynamics to describe the relative balance of → kinematic viscosity to → magnetic diffusion. It is described by: P_r = σμ₀ν = ν/η, where σ is the → conductivity of the fluid, μ₀ is the → magnetic permeability of the fluid, ν is the kinematic viscosity of the fluid, and η is the → magnetic diffusivity.

→ magnetic; → Prandtl number.

A set of points in the complex plane, the boundary of which forms a fractal with varying shapes at different magnifications. Mathematically, it is the set of all C values for which the iteration z_n+1 = z_n² + C, starting from z₀ = 0, does not diverge to infinity.

Discovered by Benoît Mandelbrot (1924-) a Polish-born French mathematician, best known as the "father of fractal geometry;" → set.

A surface with only one side, made by putting a simple twist in a long, rectangular strip of paper, then pasting the ends together.

After the German astronomer and geometer August Ferdinand Möbius (1790-1868); → band.

The eleventh of Uranus's known satellites and the innermost of Uranus' large moons. Its is about 470 km in diameter and orbits Uranus at about 130,000 km from its planet. It was discovered by Kuiper in 1948.

Miranda is a daughter of the magician Prospero in Shakespeare's The Tempest.

A band of molecular origin present in a spectrum. See for example → cyanogen band, → S star.

→ molecular; → band.

A number to be multiplied by another.

From L. multiplicandum, from multiplicandus "to be multiplied," gerundive of multiplicare, → multiply.

Bastâšow, literally "that undergoes multiplication," from bastâ, → multiple, + šow, present stem and agent noun of šodan "to become, to be, to be doing, to go, to pass," from Mid.Pers. šudan, šaw- "to go;" Av. šiyav-, š(ii)auu- "to move, go," šiyavati "goes," šyaoθna- "activity; action; doing, working;" O.Pers. šiyav- "to go forth, set," ašiyavam "I set forth;" cf. Skt. cyu- "to move to and fro, shake about; to stir," cyávate "stirs himself, goes;" Gk. kinein "to move;" Goth. haitan "call, be called;" O.E. hatan "command, call;" PIE base *kei- "to move to and fro."

Optics: Of a filter, same as → interference filter.
Radio.: Encompassing a small frequency range, typically less than 300 Hz.

→ narrow; → band.

Photometry using narrow-band filters to isolate a particular spectroscopic line or molecular band.

→ narrow band; → photometry.

A federal agency of the United States government founded in 1958 for civil aeronautical research and space exploration, superseding the National Advisory Committee for Aeronautics (NACA). Its goals include improving human understanding of the universe, the solar system, and Earth and establishing a permanent human presence in space. NASA is headquarted at Washington, D.C., and operates several research, development, and test facilities, as follows alphabetically: 1) Ames Research Center; 2) Dryden Flight Research Facility at Edwards, California, used for flight testing and as a landing site for the Space Shuttle; 3) Glenn Research Center at Cleveland, Ohio, concerned with aircraft and rocket propulsion; 4) Goddard Space Flight Center; 5) Jet Propulsion Laboratory; 6) Johnson Space center; 7) Kennedy Space Center; 8) Langley Research Center at Hampton, Virginia, which carries out research in aeronautics and space technology; 9) Marshall Space Flight Center; 10) the Space Telescope Science Institute; 11) Stennis Space Center, near Bay St Louis, Mississippi, for testing rocket engines; and 12) Wallops Flight Facility on Wallops Island, Virginia, which manages NASA's sounding rocket and scientific balloon programs.

→ national; → aeronautics; → space; administration, verbal noun of administer, from M.E. amynistre, from O.Fr. aministrer, from L. administrare "to serve, carry out, manage," from → ad- "to" + ministrare "to serve," from minister "servant, priest's assistant," from minus, minor "less," hence "subordinate," + comparative suffix *-teros.

Sâzmân, → organization; fazâyi pertaining to fazâ, → space; Âmrikâ "United State of America."

If event A must occur for event B to occur, then it is said that A is → necessary for B. If event A may cause B but there could be some other cause as well, then it is said that A is sufficient to cause B. See also → if and only if (iff).

→ necessary; → and; → sufficient; → condition.

One of the inner moons of Saturn and the outer shepherd moon for the F-ring. It was discovered in 1980 from Voyager 1 photos and is also known as Saturn XVII.

In Gk. mythology Pandora was the very first woman who was formed out of clay by the gods. She was bestowed upon humankind by Zeus as a punishment for Prometheus' theft of fire. Entrusted with a box containing all the ills that could plague people, she opened it out of curiosity and thereby released all the evils of human life.

The range of wavelengths that are transmitted by a filter. Same as → band-pass.

Pass from O.Fr. passer, from V.L. *passare "to step, walk, pass," from L. passus "step, pace;" cf. Pers. pâ "foot," pey "step;" → band.

Gozar "passage, transit, passing," from gozaštan "to pass, cross, transit," variant gozâštan "to put, to place, let, allow;" Mid.Pers. widardan, widâštan "to pass, to let pass (by);" O.Pers. vitar- "to pass across," viyatarayam "I put across;" Av. vi-tar- "to pass across," from vi- "apart, away from" ( O.Pers. viy- "apart, away;" Av. vi- "apart, away;" cf. Skt. vi- "apart, asunder, away, out;" L. vitare "to avoid, turn aside") + O.Pers./Av. tar- "to cross over"); bând, → band.

The range of → wavelengths allowed by a → filter used in a → photometric system.

→ photometric + → band.

A space observatory under development by the → European Space Agency for launch around 2024. Its objective is to detect and characterize → exoplanets by means of their → transit signature in front of a very large sample of → bright stars, and measure the seismic oscillations (→ asteroseismology) of the parent stars orbited by these planets in order to understand the properties of the exoplanetary systems.

→ planetary; → transit; → oscillation; → star.

A dimensionless number representing the ratio of the fluid viscosity to the thermal conductivity of a substance; a low number indicates high convection.

Named after the German physicist Ludwig Prandtl (1875-1953); → number.

Newton's third law of motion, which states that for every action there must be an equal and opposite reaction.

→ principle; → action; → reaction.

Information, ideas, or rumors deliberately spread widely to help or harm a person, group, movement, institution, nation, etc. (Dictionary.com).

From N.L. propaganda, short for Congregatio de Propaganda Fide, "congregation for propagating the faith," a committee of cardinals established in 1622 by Gregory XV to supervise foreign missions, from L. propagare, → propagate.

Farâtucân, from prefix farâ-, → pro-, + tucân from tucidan, → propagate.

Certain frequencies, not used for civil or military purposes (radio, television, communication channels, etc.), which are protected for research in radioastronomy, one such being 21 cm.

Protected p.p. of protect, from L. protectus, p.p. of protegere "protect, cover in front," from → pro- "in front" + tegere "to cover;" → band.

Bând, → band; negahdâridé p.p. of negahdâridan, variant of negahdâštan "to keep, behold, preserve, take care of," from negah, negâh "watch, care, custody, look" + (Mid.Pers. nikâh "look, glance, observation;" Proto-Iranian *ni-kas- "to look down," from ni- "down" (cf. O.Pers. ni preposition and verbal prefix "down;" Av. nī "down, in ,into;" Skt. ni "down," nitaram "downward;" Gk. neiothen "from below;" E. nether; O.E. niþera, neoþera "down, downward, below, beneath," from P.Gmc. *nitheraz (O.S. nithar, O.N. niðr, O.Fris. nither, Du. neder, Ger. nieder); PIE *ni- "down, below") + *kas- "to look, appear;" cf. Av. nikā-, nikāta- (in the name of the 15-th nask) "that which is observed," ākas- "to look;" Mid.Pers. âkâh, Mod.Pers. âgâh "aware, knowing;" Skt. kāś- "to become visible, appear;" Ossetic kast/kaesyn "to look") + dâridan, dâštan "to have, hold, maintain, possess" (Mid.Pers. dâštan; O.Pers./Av. root dar- "to hold, keep back, maintain, keep in mind;" cf. Skt. dhr- "to to hold, keep, preserve," dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE *dher- "to hold, support").

A precipitation consisting of rain and partially melted snow. It usually occurs when the temperature of the air layer near the ground is slightly above freezing. Called sleet in British English speaking countries, but not in the United States where the term has a different meaning in meteorology.

→ rain; → snow; → mix.

Šaliv, of dialectal origin, Kurd. šalêwa "rain and snow mixed," Aftari šelâp, Qasrâni šelâb with the same meaning, Tabari šalâb "strong cloudburst." The first element šal, šel, šor, šâr, âbšâr, šâridan "to flow." The second element iv, êw, âp, âb, → water.