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parallel of altitude
A small circle on the celestial sphere whose plane is parallel to the celestial horizon. Same as → almucantar.
A solid figure whose six bases are → parallelograms, opposite pairs being identical and parallel.
A paramagnetic substance, which possesses → paramagnetism.
Relative to or characterized by → paramagnetism.
The property of a substance that possesses a → magnetic permeability greater than that of a vacuum but significantly less than that exhibited by → ferromagnetism. In the absence of an external magnetic field the atomic → magnetic moments of the substance are randomly oriented and thus cancel each other out with no net total magnetic moment. Moreover the coupling between neighboring moments is weak. However, when a magnetic field is applied magnetic moments align with the direction of the field and so the magnetic moments add together. Therefore paramagnetic substances affect external fields in a positive way, by attraction to the field resulting in a local increase in the magnetic field. The → magnetization vanishes when the field is removed.
General: Any of a set of physical properties whose values determine the
characteristics or behavior of something. → impact parameter;
→ ionization parameter.
Parâmun, from parâ-, → para-, + mun/mân "measure," as in Pers. terms pirâmun "perimeter," âzmun "test, trial," peymân "measuring, agreement," peymâné "a measure; a cup, bowl," from O.Pers./Av. mā(y)- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum; PIE base *me- "to measure."
Fr.: équation paramétrique
Any of a set of equations that defines the coordinates of the dependent variables of a curve or surface in terms of one or more independent variables or parameters.
Fr.: Observatoire de Paranal
An → ESO observatory, located on Cerro Paranal in the Atacama Desert, northern Chile, at 2,635 m altitude. It is about 120 km south of the town of Antofagasta and 12 km inland from the Pacific Coast. The Paranal Observatory hosts the → Very Large Telescope (VLT) with four 8.2 m telescopes. Each telescope provides one → Cassegrain and two → Nasmyth focus stations for facility instruments. One Nasmyth focus is available for visitor instruments. In addition each telescope is equipped with a → coudé focus station from which the light can be coherently combined in the interferometric focus. ESO also operates four 1.8 m Auxiliary Telescopes (ATs), that are used as an interferometric array (VISA) and a 4 m infrared survey telescope (VISTA). Currently, more than 10 instruments including two interferometric instruments (MIDI, AMBER) are operational and offered for science observations.
Paranal, the name of the mountain, in the Quechua language meaning "whirlwind;" → observatory.
An astronomical and meteorological calendar written by ancient Greeks from 450 B.C. during at least three centuries. The parapegma was an inscribed stone for public use. It had holes beside the inscription, in which a peg could be inserted next to the appropriate day. The term was later applied to purely written forms of such calendars, or almanacs; plural form parapegmata.
From → para- "next to" + pegma "something that fastens something else together," from pegnyein "to stick."
Characteristic of optical analyses that are limited to infinitesimally small apertures. Also called first-order or Gaussian optics.
Fr.: rayon paraxial
A ray that lies close to and almost parallel to the optical axis and behaves according to paraxial equations.
Fr.: catalogue de Parenago
A catalog of stars in the → Orion Nebula created by P. P. Parenago in 1954 (Publ. Astr. Inst. Sternberg, Band 25, p. 393-437, Moskau).
Pavel Petrovich Parenago (1906-1960), a Soviet astronomer.
1) General: A father or a mother. A precursor, or
From O.Fr. parent, from L. parentem (nominative parens) "father or mother, ancestor," from parere "to bring forth, give birth to, produce," from PIE base *per- "to bring forth"
Fr.: nuage parent
Usually of a newborn star, the molecular cloud in which the star has formed.
Fr.: élément parent
A radioactive element that spontaneously decays into a new substance. The product of this decay is known as a "daughter" element.
Fr.: galaxie parente
Of a high redshift supernova, the galaxy in which the event has occurred.
Fr.: molécule parente
The molecule initially produced when a comet nucleus sublimates, soon changed to different daughter molecules because of solar radiation.
An atmospheric optical phenomenon, seen as a bright spot sometimes appearing at either side of the → Sun, often on a luminous ring or → halo and at the same angular elevation as the Sun. Parhelia are caused by the → refraction and → reflection of → sunlight by → ice crystals suspended in the Earth's → atmosphere. Also called mock Sun or sundog.
1) General: Equality, as in amount, status, or character;
equivalence; correspondence; similarity; analogy. Opposite of disparity.
From M.Fr. parité, from L.L. paritas "equality," from L. adj. par "equal."
Hamâli, quality noun of hamâl, → pair (equivalent 2).