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

The brightest star in the constellation → Taurus (visual magnitude about 0.9), Aldebaran is an orange K-type giant that lies 60 → light-years away. It has a faint M2 V companion. It is slowly and irregularly variable.

Ar. Aldebaran "the follower" (of the Pleiades, which rise shortly before it does), from al "the" + dabaran "follower," from dobur "to follow". Gâvcašm "the bull's eye," from Mod.Pers. Gâv "bull, cow" + cašm "eye," corresponding to the alternative Ar. name of the star Ayno 's Sowr.

The → antiparticle of a → baryon.

→ anti-; → baryon.

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.

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.