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

A band in the → absorption spectrum of → ozone (O₃) extending in the → ultraviolet from 310 nm to 370 nm. It is located at the red end of the strong → Hartley band.

W. Huggins and M. Huggins, Proc. R. Soc. London 48, 216 (1890).

Logic, Math.: An → expression indicating that two → statements so connected are → necessary and sufficient conditions for one another. The corresponding logical symbols usually used are: ↔, ⇔, ≡, and iff.

→ if; → and; → only.

State of glowing at high → temperature; white or bright-red → heat.

Quality, state noun from → incandescent.

1) (Of light) produced by → incandescence.
2) Glowing or → white with → heat.
3) Intensely → bright; brilliant (Dictionary.com).

From Fr., from L. incandescent-, incandescens, p.p. of incandescere "to become hot," from → in- + candescere "to become hot," from candere "to glow."

Foruzandé, agent noun and verbal adj. from foruzidan, → glow.

Electric lamp in which light is produced by the heating effect of a → metal  → filament.

→ incandescent; → lamp.

Statistics: Two random variables X and Y if and only if the value of X has no influence on the value of Y and vice versa.

→ dependent; → random; → variable.

The function which is being integrated in a given integral.

From L. integrandum, noun use of neuter of integrandus, gerundive of integrare, → integrate.

Dorostâlân, pr.p. of dorostâlidan, → integrate.

A tract of land completely surrounded by water, and not large enough to be called a → continent (Dictionary.com).

M.E. iland, from O.E. igland "island," from ieg "island;" PIE *akwa- "water," cf. Pers. âb, → water, + → land.

Âdâk, âdak, adak "island" (Dehxodâ), probably from Proto-Ir. *āpdaka- "placed in water," from *âp-, → water, cf. Pers. âb, + *da- "to place, put," cf. Pers. dâdan "to give," → thesis, + suffix *-ka.
Âbxost, ultimately from āpxvasta-, literally "stricken/pounded by water," from *āp-, → water, + *xvasta-, from Proto-Ir. *huah- "to strike, to thresh;" cf. Av. (paiti)xv^anh- "to thresh;" Mid.Pers. xwastan "to tread, trample, thresh;" Mod.Pers. xvast "trampled, beaten," âbxun "island," šabixun "night attack;" Kurd. xistin, xin-, xa- "to strike, to beat;" Hamedâni xostan/xus-, Esfahâni xosan "to throw."
Jaziré loan from Ar. jazirah.
Tomb "island" in Iranian Hormozgâni dialects.

The hypothesis first put forward by Immanuel Kant (1724-1804) according to which the objects termed "spiral nebulae" were stellar systems comparable to our own → Milky Way galaxy. At the end of the 18th century, William Herschel (1738-1822) using his giant reflectors discovered thousands of such nebulae. However, in spite of advances in observations it was never possible to prove Kant's idea until the second decade of the twentieth century. The observations using the Mount Wilson 2.50m (100 inch) telescope allowed Edwin Hubble in 1924 to firmly establish that the "spiral nebulae" were unquestionably extragalactic.

The term "island Universe" was first introduced by the German Alexander von Humboldt in 1850; → island; → Universe.

Any part of the earth's surface not covered by a body of water.

M.E., from O.E. land, lond, "ground, soil, territory;" PIE base *lendh- "land, heath" (cf. O.N., O.Fris. Du., Ger., Goth. land; O.Ir. land; Welsh llan "enclosure, church," Breton lann "heath," source of Fr. lande; O.C.S. ledina "waste land, heath," Czech lada "fallow land").

Xoški, from xošk, → dry, + noun suffix -i; zamin "land, → earth."

A coastal breeze blowing from land to sea after sunset, caused by the temperature difference when the sea surface is warmer than the adjacent land. The warmer air above the water continues to rise, and cooler air from over the land replaces it, creating a breeze.

Land, → lander; → breeze.

Xoški "land," from xošk "dry;" Mid.Pers. xušk "dry;" O.Pers. uška- "mainland;" Av. huška- "dry;" cf. Skt. śuska- "dry, dried out;" Gk. auos "dry, dried up;" O.E. sēar "dried up, withered;" Lith. sausas "dry, barren."

The process wherein a → plasma gains energy at the expense of the → Langmuir wave. In the presence of the → Landau resonance, the particles in resonance moving slightly faster than the wave lose energy, while those moving slightly slower will gain energy. Since the Maxwellian distribution is decreasing with velocity, in a Maxwellian plasma, near the Landau resonance, there are more particles at lower velocities than at higher velocities. Also called collisionless damping.

Lev Landau (1908-1968), a prominent Soviet physicist, 1962 Nobel Prize in Physics for his development of a mathematical theory of → superfluidity; → damping.

The → energy level which can be occupied by a → free electron in a → magnetic field.

→ Landau damping; → level.

For parallel propagating → electrostatic waves in a → plasma, the → resonance which occurs when the particle velocity equals the parallel phase velocity of the wave.

→ Landau damping; → damping.

The constant of proportionality relating the separations of lines of successive pairs of adjacent components of the levels of a spectral multiplet to the larger of the two J-values for the respective pairs. The interval between two successive components J and J + 1 is proportional to J + 1.

After Alfred Landé (1888-1976), a German-American physicist, known for his contributions to quantum theory; → facteur.

A → space probe designed to land on a → planet or other solid → celestial body.

→ land; → -er.

See → Fleming's rules.

→ left; → hand; → rule.

Using the left hand with greater ease than the right.

→ left; → hand + -ed.

Capâl, from cap, → left, + -al, → -al. Capdast, with dast, → hand.

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.

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

→ lunar; → highland.