Aldebaran (α Tauri)
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.
1) bâr (#); 2) milé (#)
Fr.: 1) bar; 2) barre
1) A unit of → pressure, not belonging to the
→ International System (SI),
equivalent to 106→ dynes
per cm2 and 0.987 → atmospheres.
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."
1) Loan from Fr., as above.
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.
Fr.: étoile à barium
adasi-ye Barlow (#)
Fr.: lentille de Barlow
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.
Fr.: boucle de Barnard
A very faint nebular shell of huge size enveloping the central portion of Orion.
Fr.: étoile de Barnard
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.
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.
Fr.: instabilité barocline
1) A type of instability occurring within a rapidly → rotating star
where non-axisymmetric motions can separate surfaces of constant pressure from
→ equipotential surfaces.
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.
Instrument for measuring the atmospheric pressure. It is used in determining height above sea level and predicting changes in weather.
qânun-e fešârsanji, ~ fešârsanjik
Fr.: loi barométrique
The atmospheric pressure decreases exponentially from any reference surface as the altitude increases.
In a fluid, conditions where surfaces of constant pressure are parallel to surfaces of constant temperature. This state is equivalent to zero → baroclinicity.
Fr.: gaz barotrope
A gas whose density is a function solely of pressure.
Fr.: instabilité barotrope
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.
A state of a fluid in which the surfaces of constant density coincide with surfaces of constant pressure (isobaric).