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

In physics, specifically statistical mechanics, the state of an atomic or molecular system in which the number of members in an excited state is larger than those in lower energy states. → optical pumping; → inverted population.

→ population; → inversion.

1) A part of any whole, either separated from or integrated with it.
2) To divide into or distribute in portions or shares.

M.E. porcion, from O.Fr. porcion "part, portion, share," from partion- "share, part, piece," related to pars, → part.

Pâreš, from pâr "part, portion, piece" (variants pâré, parré "portion, segment (of an orange)," pargâlé, "piece, portion; patch;" (dialects Kermâni pariké "portion, half;" Tabari perik "minute quantity, particle;" Lârestâni pakva "patch;" Borujerdi parru "patch"); Mid.Pers. pârag "piece, part, portion; gift, offering, bribe;" Av. pāra- "debt," from par- "to remunerate, equalize; to condemn;" PIE *per- "to sell, hand over, distribute; to assigne;" Gk. peprotai "it has been granted;" L. pars, as above; Skt. purti- "reward;" Hitt. pars-, parsiya- "to break, crumble") + -eš suffix.

1a) Condition with reference to place; location; situation.
1b) A place occupied or to be occupied. → mean position.
2a) To put in a particular or appropriate position; place.
2b) To determine the position of; locate.

M.E. posicioun, from O.Fr. posicion, from L. positionem "act or fact of placing, position, affirmation," from positus, p.p. stem of ponere "to put, place."

Neheš, verbal noun from nehâdan "to place, put; to set;" Mid.Pers. nihâtan, from ne-, ni- "down; into," → ni- (PIE), + dâ- "to put; to establish; to give," dadâiti "he gives;" cf. Skt. dadâti "he gives;" Gk. didomi "I give;" L. do "I give;" PIE base *do- "to give"). Neheš-dâdan, from neheš "position," + dâdan "to give, yield, put," → datum.

The convention for measuring angles on the sky in astronomy (Abbreviated as PA). It is the direction of an imaginary arrow in the sky, measured from north through east: 0° = north, 90° = east, 180° = south, and so on to 359° and back to 0°. Applied to a binary system it is the direction of a secondary body or feature from a primary, measured in the system. .

→ position; → angle.

In single dish astronomy, an observing mode in which the telescope is moved between the object position and a user defined reference position. The aim is to eliminate unwanted signals in the baseline. → beam switching; → frequency switching.

→ position; → switching.

Relating to or determined by position.

→ position; → -al.

The branch of astronomy that is used to determine the location of objects on the celestial sphere, as seen at a particular date, time, and location on the Earth. Same as → spherical astronomy.

→ positional; → astronomy.

A system of representing → numbers in which the → position of a → digit in a string of digits affects its value. The decimal system is a positional notation for expressing numbers. Same as → place-value notation and → positional number system.

→ positional; → notation.

A → number system in which the value of each digit is determined by which place it appears in the full number. The lowest place value is the rightmost position, and each successive position to the left has a higher place value. In the → number system conversion, the rightmost position represents the "ones" column, the next position represents the "tens" column, the next position represents "hundreds", etc. The values of each position correspond to powers of the → base of the number system. For example, in the usual decimal number system, which uses base 10, the place values correspond to powers of 10. Same as → place-value notation and → positional notation. See also → number system conversion.

→ positional; → number; → system.

The act or process of putting in a particular position or determining the psition of.

Verbal noun of → position; → -ing.

Same as → direct correlation.

→ positive; → correlation.

1) The act or fact of possessing; the state of being possessed.
2) A thing possessed (Dictionary.com).

→ possess; → -tion.

Dârešt, verbal noun of dâštan "to have, possess" (on the model of konešt, from kardan; xoršt, from xordan; bâlešt, from bâlidan; râmešt, from râmidan; (Lori) zenešt, from zadan; (Nowdân, Fârs) perešt, from paridan); Mid.Pers. dâr-, dâštan "to have, hold, preserve;" O.Pers./Av. dar- "to hold, keep back, maintain, keep in mind;" Skt. dhr- "to hold, keep, preserve," dharma- "what is established or firm; law;" Gk. thronos "elevated seat, throne," L. firmus "firm, stable," Lith. daryti "to make," PIE *d^her- "to hold, support."

→ post-Newtonian formalism.

→ post-; → Newtonian; → expansion.

A function of the form f(x) = xⁿ, where n is a → real number.

→ power; → function.

For a → random variable X, any → distribution which has the form: P(X ≥ x) = (k/x)^α, where x is a value in the range defined for X, k > 0 is a parameter termed location parameter, and α > 0 is the → slope parameter.

→ power; → law; → distribution.

A professional man, especially in medicine and the law.

Alteration of practician, → practice (+ -ian) + -er, → -or.

Varzmand, from varz, → practice, + -mand, → -ist.

A technique in spectroscopy which uses a combination of several dispersive elements (prisms in series or a grism) before focusing the light on the primary disperser, usually a grating, in order to achieve high spectral resolutions.

→ pre-; → dispersion.

The periodic motion of the → rotation axis of a body such as a → spinning top in which the axis of rotation gradually sweeps out a conical shape. In the case of the spinning Earth, it is due to the combined → gravitational attractions of the → Sun, the → Moon, and → planets on Earth's → equatorial bulge. Since the Earth's axis is tilted to its → orbital plane or → ecliptic, the gravitational force of the Sun and the Moon on the Earth's equatorial bulge tend to pull it back toward the plane of ecliptic. As a result, the axis → precesses. Earth's axis of rotation precesses with a period of about 25,770 years, describing one complete circle on the → celestial sphere (→ precession constant). This circle has a radius of approximately 23°.5, equal to the → inclination of the Earth's orbit. Since the → vernal equinox is the reference direction for the → equatorial coordinate system, the coordinates of "fixed" objects change with time and must therefore be referred to an → epoch at which they are correct. → sign of zodiac.
See also → general precession; → precession of the ecliptic; → precession of the equator; → precession of the equinoxes; → precessional circle; → precession time; → geodetic precession; → general precession in longitude; → general precession in right ascension; → orbital precession; → perihelion precession; → planetary precession; → precession period.

L.L. præcissionem "a coming before," from L. præcessus, p.p. of præcedere "to happen before," from the fact that the equinoxes occur earlier each year with respect to the preceding year, from præ- "before," → pre-, + cedere "to walk, to go, to happen."

Pišâyân, literally "coming before," from piš- "before" → pre- + ây- (present stem of âmadan "to come, arrive, become"), from Av. ay- "to go, to come," aēiti "goes;" O.Pers. aitiy "goes;" Skt. e- "to come near," eti "arrival;" L. ire "to go;" Goth. iddja "went," Lith. eiti "to go;" Rus. idti "to go;" + -ân suffix of space and time.

The amount by which the equinoctial points drift westward annually due to precession. Its value for epoch J2000.0 is 50''.26, resulting from the westward → precession of the equator (50".38), and the eastward → precession of the ecliptic (0".12).

→ precession; → constant.

The component of general precession caused by the gravitational attraction of the planets on the Earth's center of mass. It causes the equinox to move eastward by about 0''.12 per year in the opposite direction to the → precession of the equator. This terminology replaces → planetary precession, according to an IAU resolution adopted in August 2006.

→ precession; → ecliptic.