An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 753
Delta Cephei

Fr.: Delta Cephée   

The prototype of classical → Cepheid variables, which is a pulsating → yellow supergiant. John Goodricke was the first in 1784 to discover its variability. The star shows a quick and sharp rise from minimum to maximum, and slowly declines to its minimum again. The changes in brightness are accompanied by and principally caused by changes in stellar temperature and also by changes in radius. δ Cephei was actually the second Cepheid variable to be discovered. The first one, Eta Aquilae, had been discovered earlier the same year by Edward Pigott. δ Cephei varies with a period of 5.366341 days (or 5 days 8 hours 37.5 minutes) from magnitude 3.48, spectral type F5 Ib in its maximum to magnitude 4.37, spectral type G2 Ib in its minimum. It lies at a distance of 1,340 → light-years.

delta; Cephei, genitive of → Cepheus.

delta drive
  رانه‌ی ِ دلتا، ~ واکیل   
râne-ye deltâ , ~ vâkil

Fr.: entraînement en déclinaison   

The → mechanism that imparts or transfers power to a → telescope so that it can move along the → declination direction. See also → tracking.

delta; → drive.

delta function
  کریای ِ دلتا   
karyâ-ye delta

Fr.: fonction delta   

Same as → Dirac function.

delta offset
  اپنه ِ دلتا   
apneh-e deltâ

Fr.: offset en déclinaison   

A short distance from the target, in → declination, where the → telescope is pointed for various purposes.

delta; → offset.

Delta Orionis
Deltâ Šekârgar

Fr.: delta Orionis   

Same as → Mintaka.

delta; → Orion.

Delta Scuti variable
  ورتنده‌ی ِ دلتا-سپر   
vartande-ye δ-Separ

Fr.: variable δ Scuti   

A member of a class of → pulsating stars with periods less than 0.3 days, → spectral types A or F, and visual light amplitudes in the range from a few thousands of a magnitude to about 0.8 mag. On the → H-R diagram, δ Scuti stars form a group which lies in an → instability strip which includes the classical → Cepheids at its brightest end and the pulsating → white dwarfs at its faintest limit. These stars can show very complex light variations since, while some of them are pulsating in one radial mode only, others may be pulsating simultaneously in several radial and non-radial modes.

Named after the prototype star δ of constellation → Scutum; → variable.

Delta T
Deltâ T (ΔT)

Fr.: Delta TT)   

A measure of the variation in → Earth's rotation, which is the difference between → Terrestrial Time (TT) and → Universal Time (UT). TT is uniform and related to the → International Atomic Time, whereas UT, which is directly tied to the Earth's rotation, is not strictly uniform and shows small erratic fluctuations. Between 1970 and 1990, ΔT changed from +40 to +57 seconds, and was +67 seconds for 2010.

Δ, Gk. letter of alphabet indicating a difference; T for → time.


Fr.: démodulation   

In communications, the process of recovering the original information from a modulated signal wave. → modulation.

de- + → modulation

pari (#)

Fr.: démon   

An imaginary intelligent entity introduced in several → thought experiments, such as → Laplace's demon and → Maxwell's demon.

From L. dæmon "spirit," from Gk. daimon "deity, fate, fortune."

Pari "a good genius, a fairy," from Mid.Pers. parîk "sorceress, witch;" from Av. pairikā- "sorceress, witch."


Fr.: démontrer   

1) To make evident or establish by arguments or reasoning; prove.
2) To describe, explain, or illustrate by examples, specimens, experiments, or the like.
3) To manifest or exhibit; show.
4) T display openly or publicly, as feelings (

From L. demonstratus, p.p. of demonstrare "to show, point out," from → de- + monstrare "to show," from monstrum "sign, portent."

Padišidan, from Sogd. padēš "to show," ultimately from Proto-Ir. *apa-dais-, from *dais- "to show," cf. Av. daēs- "to show," related to andiš, → think.

  پدیش، پدیشش   
padiš, padišeš

Fr.: démonstration   

1) The → act or → circumstance of proving or being → proved conclusively, as by → reasoning or a show of → evidence.
2) Something serving as → proof or supporting evidence.
3) An exhibition, as of feeling; display; → manifestation (

Verbal noun of → demonstrate.


Fr.: démonstrateur   

A person or thing that demonstrates (

demonstrate; → -or.


Fr.: démystification   

The removal of mystery or confusion surrounding a topic or idea.

demystify; → -tion.


Fr.: démystifier   

To rid of mystery or obscurity; clarify. The removal of mystery or confusion surrounding a topic or idea.

de-; → mystify;


Fr.: dendrite   

1) A branching treelike figure produced on or in a mineral by a foreign mineral.
2) A crystallized → arborescent form.
3) Any of the usually branching protoplasmic processes that conduct impulses toward the body of a neuron (

From Gk. dendrites "of or pertaining to a tree," from dendron "tree," cognate with Pers. deraxt, variant dâr, → tree.

Šâxzâré, from šâxzâr, from šâxsâr "full of branches," from šâx, šâxé, → branch, + suffix -zâr denoting profusion, and abundance, as in kârzâr "a field of battle; combat" šurezâr "unfertile, salty ground; nitrous earth," xoškzâr "arid land," and so forth.

dâršenâsi (#)

Fr.: dendrologie   

The branch of → botany dealing with trees and shrubs. Dendrology studies the distinguishing characteristics of tree species for the purpose of identification and classification into orders and other natural groups.

From dendro- a combining form meaning "tree," from Gk. dendron "tree," related to Pers. dâr, → tree, + → -logy.

Deneb (α Cygni)
Zanab (#)

Fr.: Deneb   

The brightest star, of magnitude V = 1.25, in the constellation → Cygnus. It is a → supergiant of → spectral type A2 Ia.

Deneb "tail," from Ar. dhanab ad-dajajah (ذنب الدجاجه) "tail of the hen," referring to the legendary swan (Cygnus) in Gk. mythology.

Zanab, from Ar., as above.

Denebola (β Leonis)
  شیردم، ذنب الاسد   
Širdom, Zanab-ol-asad (#)

Fr.: Denebola   

The second brightest star, of magnitude V = 2.14, in the constellation → Leo. A → main sequence star of → spectral type A3 V.

Denebola, from Ar. dhanab al-asad (ذنب الاسد) "tail of the lion," referring to the lion in Gk. mythology.

Širdom "tail of the lion," from šir "lion" → Leo + dom "tail," → comet. Zanab-ol-asad from Ar., as above.


Fr.: dénégation, démenti   

1) An assertion that something said, believed, alleged, etc., is false.
2) Refusal to believe a doctrine, theory, or the like.
3) Disbelief in the existence or reality of a thing (

deny; → -al.


Fr.: dénommer   

1) To give a specific name to.
2) To express in a multiple of a unit of measurement.

de-; → nominate.

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