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

A series of hydrogen → spectral lines (Hα, Hβ, Hγ, and others) that lies in the visible portion of the spectrum and results when electrons from upper → energy levels (n > 2) undergo → transition to n = 2.
Historically, Balmer emission lines (mainly Hα) from ionized nebulae were first observed by O. Struve and C. T. Elvey (1938, ApJ 88, 364). This was an important indication of the existence of hydrogen, in the ionized state, in the → interstellar medium.

→ Balmer; → series.

General:1) A strip serving to encircle and bind one object or to hold a number of objects together. 2) A strip or stripe that contrasts with something else in color, texture, or material.
Physics: 1) A specific range of wavelengths or frequencies of electromagnetic radiation.
2) Closely packed spectral lines that appear to form a continuous group. → absorption band; → emission band.

From M.E. bende, O.E. bend, from O.Fr. bande, bende, P.Gmc. *bindan, from PIE *bendh- "to bind" (cf. Goth bandi "that which binds;" Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," bandhah "a tying, bandage."

Bând, adoption from E. band, which is cognate and synonymous with Pers. band, present tense stem of bastan "to bind, shut," Mid.Pers. bastan, band, Av./O.Pers. band-, as explained above. See also → strip.

A location on the spectrogram of a molecule at which the lines of a band stack.

Band head, from → band + head, from O.E. heafod "top of the body," also "upper end of a slope," also "chief person, leader," from P.Gmc. *khaubuthan, from PIE *kauput- "head" (cf. Skt. kaput-, L. caput "head," Lori kapu "head," kapulek "skull, middle of the head").

Bândsar, from → bând + sar "head," soru, sorun "horn," karnâ "a trumpet-like wind instrument" (originally made from animal horns), variant sornâ "a wind instrument;" Mid.Pers. sar "head," sru "horn;" Av. sarah- "head," srū- "horn, nail;" cf. Skt. śiras- "head, chief;" Gk. kara "head," karena "head, top," keras "horn;" L. cornu "horn," cerebrum "brain;" P.Gmc. *khurnaz (E. horn; Ger. Horn, Du. horen), from PIE *ker- "head, horn."

A spectrum which consists of a number of bands each having one sharp edge. Each band is composed of a large number of closely spaced emission or absorption lines. Band spectra are typical of molecules. Bands produced by titanium oxide, zirconium oxide, and carbon compounds are characteristic of low temperature stars.

Band spectrum, from → band + → spectrum.

Binâb-e bândi, from binâb, → spectrum + bândi, relating to bând, → band.

A range of frequencies that can pass through a filter such as one in an electrical circuit.

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

Gozar-bând, from gozar "passage, transit, passing," gozaštan "to pass, cross, transit," from Mid.Pers. vitârtan + bând, → band.

An electric filter that transmits a known band of frequencies but suppresses unwanted frequencies above and below this band.

→ bandpass; → filter.

The portion of the electromagnetic spectrum that is permitted to pass through an electronic device, such as a radio telescope detector. The term refers to either a wavelength interval or a frequency interval.

Bandwidth, from → band + → width.

Bândpahnâ, from bând, → band, + pahnâ, → width, from pahn "wide," → broad.

1) A unit of → pressure, not belonging to the → International System (SI), equivalent to 10⁶→ dynes per cm² and 0.987 → atmospheres.
2) → stellar bar, → galactic bar, → barred spiral galaxy.

1) From Gk. baros "weight," cf. Skt guru, L. gravis; PIE *gwere- "heavy;" cf. Pers. bâr "weight," gerân "heavy," L. brutus "heavy, dull, stupid, brutish," Skt. bhara- "burden, load," bharati "he carries;" PIE *bher- "carry, give birth."
2) From O.Fr. barre, from V.L. *barra "bar, barrier," or perhaps from Gaulish *barro "summit."

1) Loan from Fr., as above.
2) Mile, from Ar. mil "any long and narrow piece of metal," + -é noun suffix.

A whitish, malleable, metallic → chemical element; symbol Ba. → Atomic number 56; → atomic weight 137.33; → melting point 725°C; → boiling point 1,640°C; → specific gravity 3.5 at 20°C. Barium was discovered by the Swedish pharmacist and chemist Carl Wilhelm Scheele in 1774. It was first isolated by the British chemist Humphry Davy in 1808.

From Mod.L., from Gk. barys "heavy," from the mineral barytes "heavy spar" (BaSO₄), in which the element was discovered; cognate with Pers. bâr "weight," → bar.

A type of star, usually G or K → giants, whose spectra show unusually strong absorption lines of → barium, → strontium, and other → s-process elements.

→ barium; → star.

A → negative lens placed in a telescope between the → objective and the → ocular. Its diverging action reduces the convergence of the light cone, forming a larger image at a slightly greater distance.

Peter Barlow (1776-1862), English physicist; → lens.

In nuclear physics, unit of area for measuring the cross-sections of nuclei. 1 barn equals 10^-24 sq. cm.

Barn, from O.E. bereærn "barn," lit. "barley house," from bere "barley" + aern "house." The use of barn in nuclear physics comes from the fact that the term denotes also "an unexpectedly large quantity of something." It seems that when physicists were first studying nuclear interactions, they found out that the interaction probabilities, or cross-sections, were far more larger than expected; the nuclei were `as big as a barn'.

From Edward Emerson Barnard (1857-1923) American astronomer who made several obserational discoveries.

A very faint nebular shell of huge size enveloping the central portion of Orion.

Named after → Barnard, who discovered the loop in 1895; → loop.

A → red dwarf in the constellation → Ophiuchus discovered in 1916 by E.E. Barnard, that until 1968 had the largest → proper motion of any star. It moves on the sky 10.3 arcseconds per year, which means that it travels the equivalent of a lunar diameter every 180 years. It is the second nearest star system to the Sun.

In honor of → Barnard; → star.

A prefix meaning → pressure used in the formation of compound words, such as → baroclinic, → barometer, → barotropic.

Baro- combining form of Gk. baros "weight;" cognate with Pers. bâr "weight," gerân "heavy;" cf. Skt. guru, L. gravis; PIE *gwere- "heavy;" L. brutus "heavy, dull, stupid, brutish;" Skt. bhara- "burden, load," bharati "he carries;" PIE *bher- "carry, give birth."

Fešâr-, → pressure.

Of, pertaining to, or characterized by → baroclinicity. Sometimes called → barocline.

→ baro-; → -cline; → -ic.

1) A type of instability occurring within a rapidly → rotating star where non-axisymmetric motions can separate surfaces of constant pressure from → equipotential surfaces.
2) A hydrodynamic instability associated with a baroclinic layer of the atmosphere. It arises from temperature variation along the pressure surfaces. Baroclinic instability is associated with the vertical → shear of the mean flow, which is related to the horizontal temperature gradient by the thermal wind equation. Instabilities in a baroclinic region grow by converting potential energy associated with the mean horizontal temperature gradient into kinetic energy through ascending warm air and descending cold air (Rasmussen & Turner (eds.), Polar Lows, Cambridge Univ. Press, 2003).

→ baroclinic; → instability.

The state of stratification in a fluid in which surfaces of constant pressure do not coincide with those of constant density, but intersect. Where baroclinicity is zero, the fluid is → barotropic. Same as baroclinity.

→ baroclinic; → -ity.

Instrument for measuring the atmospheric pressure. It is used in determining height above sea level and predicting changes in weather.

→ baro- + → -meter.