Delta Scuti variable
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.
Deltâ T (ΔT)
Fr.: Delta T (ΔT)
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.
In communications, the process of recovering the original information from a modulated signal wave. → modulation.
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."
1) To make evident or establish by arguments or reasoning; prove.
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.
1) The → act or → circumstance
of proving or being → proved conclusively, as
by → reasoning or a show of → evidence.
Verbal noun of → demonstrate.
A person or thing that demonstrates (Dictionary.com).
The removal of mystery or confusion surrounding a topic or idea.
To rid of mystery or obscurity; clarify. The removal of mystery or confusion surrounding a topic or idea.
1) A branching treelike figure produced on or in a mineral by a foreign
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.
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.
Deneb (α Cygni)
Deneb "tail," from Ar. dhanab ad-dajajah (
Zanab, from Ar., as above.
Denebola (β Leonis)
Širdom, Zanab-ol-asad (#)
Denebola, from Ar. dhanab al-asad (
Fr.: dénégation, démenti
1) An assertion that something said, believed, alleged, etc., is false.
1) To give a specific name to.
Fr.: groupe, catégorie, unité; dénomination
1) A name or designation.
Verbal noun of → denominate.
The quantity y in a fraction x/y. The quantity x is the → numerator.
1) To condemn or censure openly or publicly.
Having relatively high → density.
From L. densus "thick, crowded," cognate with Gk. dasys "hairy, bushy, thick grown."
Cagâl "dense, thick," related to ceqer "stiff, hard, tough, firm" (dialectal Kermâni ceqel, Šândizi caqal), caqâlé "stiff, unripe fruit."
Fr.: coeur dense
An opaque region of a → molecular cloud (AV 10 mag) which is considered to be the progenitor of → star formation. Dense cores have temperatures of about 10 K and masses of roughly 1 to 10Msun each and in which the → molecular hydrogen density is roughly 104-105 cm-3 and size 0.1 pc. The → self-gravity of a dense core plays a central part in star formation. See also → hot molecular core.