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

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.

The external covering on the trunks, boughs, and branches of trees.

M.E., from O.Norse börkr "bark."

Kâlun, from Mâzandarâni kâlun "bark," variants (Dâmqân) kul "bark," (Tâti) lo "bark," (Yazd, Mâzandarân) kol "bark," (Nâin) kuluz "egg shell," (Aftar) cokola "egg shell, pistaschio shell," pukel, → shell, keler, → scalp, probably related to (Khotan Sacca) karastra- "fur garment," (Waxi) kurust "bark of tree," from PIE root *(s)ker- "to cut off," from which are derived L. cortex "bark," corium "thick skin," scortum "hide," and Persian carm "leather."

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.

A law which describes the vertical pressure distribution in the lower parts of Earth's atmosphere. The atmospheric pressure decreases exponentially from any reference surface as the altitude increases.

→ barometer; → law.

In a fluid, conditions where surfaces of constant pressure are parallel to surfaces of constant temperature. This state is equivalent to zero → baroclinicity.

→ baro-; → -tropic.

A gas whose density is a function solely of pressure.

→ barotropic; → gas.

A hydrodynamical instability that arises when the horizontal → shear gradient becomes very large. Barotropic instabilities grow by extracting kinetic energy from the mean flow field.

→ barotropic; → instability.

A state of a fluid in which the surfaces of constant density coincide with surfaces of constant pressure (isobaric).

→ barotropic gas.

Having a bar like structure.

→ bar.

A transitional class of object between the classic spiral galaxies and true irregular systems. The → Large Magellanic Cloud, the nearest and best studied example of the class, is, contrary to popular opinion, not an irregular galaxy. The LMC and other members of the SBm class have definite structural signatures. They are generally dominated by a pronounced asymmetric bar -- one that is offset from the optical center of the galaxy -- with a nascent spiral arm emanating from one end. As is the case with irregular galaxies, the optical centers of SBm type systems are not particularly special places. Disk systems later than Sc characteristically lack a central stellar concentration in addition to having weak spiral structure; this is true of SBm-type galaxies. SBm galaxies are typically very active in their star formation activity, often containing a large star-forming complex situated at one end of the bar. Beyond these general trends there is a tremendous amount of dispersion in physical properties within the SBm class, particularly in the strength of the spiral structure. At one extreme are the "one-armed" spirals such as NGC 3664 and NGC 4027 which are dominated by single, looping spiral arm. On the other hand NGC 4861 shows little evidence of spiral structure and it is dominated by a large star-forming complex at one end of its bar. The class smoothly leads to the Barred Magellanic irregulars (IBm) which show no indication of spiral structure (Wilcots et al. 1996, AJ 111, 1575).

→ Magellanic; → spiral; → galaxy.

A → spiral galaxy that exhibits a bar-shaped structure in its nucleus. → galactic bar.

→ barred; → spiral; → galaxy.