An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < Jab jet Jov Jur > >>

Number of Results: 69
Jovian planet
  سیاره‌ی ِ هرمزی   
sayyâre-ye Hormozi

Fr.: planète jovienne   

A planet that does not have a well-defined → solid  → crust, such as any of the four Solar System outer, gaseous planets: → Jupiter, → Saturn, → Uranus, and → Neptune.

Jovian; → planet.

Joy's law
  قانون ِ جوی   
qânun-e Joy

Fr.: loi de Joy   

Sunspot pairs or groups are tilted with the → leader spots closer to the equator than the → follower spots. The tilt of bipolar sunspot pairs increases with latitude.

Alfred Harrison Joy (1882-1973), an American astronomer; → law.

  ۱) دادرس، داور؛ ۲) داوری کردن   
1) dâdras (#), dâvar; 2) dâvari kardan

Fr.: 1) juge; 2) juger   

1a) A public officer authorized to hear and decide cases in a court of law; a magistrate charged with the administration of justice.
1b) A person qualified to pass a critical judgment.
2a) To pass legal judgment on; pass sentence on (a person).
2b) to form a judgment or opinion of; decide upon critically (

M.E. jugen, from Anglo-Fr. juger, O.Fr. jugier "to form an opinion about; make a decision," also "to try and pronounce sentence upon (someone) in a court," from Anglo-Fr juger, O.Fr. jugier "to judge, pronounce judgment; pass an opinion on," from L. iudicare "to judge, to examine officially; form an opinion upon; pronounce judgment," from iudicem "a judge," a compound of ius "right, law," → just, + root of dicere "to say."

Dâdras "justice administrator," from dâd, → justice, + ras present stem and agent noun of rasidan "to attain, to arrive, to mature," → access.

dâvari (#)

Fr.: jugement   

11 An act or instance of judging.
2) The ability to judge, make a decision, or form an opinion objectively, authoritatively, and wisely, especially in matters affecting action; good sense (

judge; → -ment.

  داورانه، داوریک   
dâvarâné, dâvarik

Fr.: judiciaire   

1) Pertaining to judgment in courts of justice or to the administration of justice: judicial proceedings; the judicial system.
2) Pertaining to courts of law or to judges; judiciary: judicial functions.
3) Of or relating to a judge; proper to the character of a judge; judgelike: judicial gravity.
4) Inclined to make or give judgments; critical; discriminating: a judicial mind.
5) Decreed, sanctioned, or enforced by a court (

From L. iudicalis "of or belonging to a court of justice," from iudicium "judgment, decision," from iudicem, → judge.

Dâvarâné, dâvarik, of or relating to dâvari, → judgment.

Julian calendar
  گاهشمار ِ یولیانی   
gâhšomâr-e Yuliyâni (#)

Fr.: calendrier julien   

A → solar calendar established by Julius Caesar in 46 B.C. to replace the → Roman calendar. It was inspired by the Egyptian calendar year of 365 days. The astronomer Sosigenes set up the months (January to December) and added an extra day in February every fourth year (→ leap year). This gave an average year of 365.25 days. The Julian calendar remained unchanged for 1,600 years, and was replaced by the → Gregorian calendar to correct its errors. The Roman calendar before the reform was running 80 days out of alignment with the seasons of a true year. Sosigenes fixed the calendar by having 445 days in the year 46 B.C., which brought the seasons in line with the calendar. The year 45 B.C. is known as the first leap year of the Julian calendar. However, Sosigenes' work was misinterpreted and they were placing leap years every 3 years instead of every 4 years.

Julian, adj. of L. Julius.

Julian date (JD)
  گاهداد ِ ژولی‌ین   
gâhdâd-e žulian

Fr.: date julienne   

A timekeeping system which does not have months and years. It is used primarily by astronomers to avoid confusion due to the use of different calendars at different times and places. Julian date is the interval of time in days and fractions of a day since noon 1 January 4713 B.C. (12h Universal Time). For example, January 1, 1970 is JD 2440588. Decimal fractions correspond to fractions of a day so that, for example, an observation made at 15h on June 24, 1962 is given as JD 2437840.13. → modified Julian date (MJD). Note that the "Julius" involved is not Julius Caesar, and this system is unrelated to the Julian calendar, as explained below.

The system was proposed by the French scholar Joseph Justus Scaliger (1540-1609) in 1583 and named after his father, Julius Caesar Scaliger. His choice of starting year was based on the convergence in 4713 B.C. of three calendrical cycles (indication cycle, Metonic cycle, and solar cycle). → date.

Julian day
  روز ِ ژولی‌ین   
ruz-e žulian (#)

Fr.: jour julien   

Same as → Julian date.

Julian date; → day.

Julian epoch
  زیمه‌ی ِ یولیانی   
zime-ye Yuliyâni

Fr.: époch julienne   

A way of specifying the date as a year with a decimal based on the Julian year of 365.25 days and the Barycentric Dynamical Time (TDB). The standard epoch currently in use is J2000.0, which corresponds to January 1, 2000 12:00 Terrestrial Time.

Julian calendar; → epoch.

Julian year
  سال ِ یولیانی   
sâl-e yuliyâni (#)

Fr.: année julienne   

A period of 365.25 days adopted in the Julian calendar for the length of the year.

Julian calendar; &rarr ;year.

jaheš (#)

Fr.: saut   

A point of discontinuity in a function or a derivative of a function.

Etymology unclear, probably akin to L.G. gumpen "to jump."

Jaheš, verbal noun of jahidan, jastan "to jump, to leap," from Mid.Pers. jastan, jahidan "to jump," figuratively "to happen, occur;" Av. yaēš-, yas- "to boil;" cf. Skt. yas-, yásyati "to boil, to heat; to make effort."

jump conditions
  بوتارهای ِ جهش   
butârhâ-ye jaheš

Fr.: conditions de saut   

Very different values of pressure and density (or temperature or energy) across a shock wave.

jump; → condition.


Fr.: jonction   

In a → semiconductor device, a region of transition between semiconducting regions of different electrical properties.

Junction "act of joining," from L. junctionem, noun of action from jungere "to join," cognate with Pers. yuq, juhé, as below; PIE base *yeug- "to join,"

Juheš, from juh, variant of yuq "yoke," Mid.Pers. jug, ayoxtan "to join, yoke;" Av. yaog- "to yoke, put to; to join, unite;" cf. Skt. yugam "yoke;" Hittite yugan "yoke;" Gk. zygon "yoke," zeugnyanai "to join, unite;" L. jungere "to join," as above; O.C.S. igo, O.Welsh iou, Lith. jungas O.E. geoc.

kehtar (#)

Fr.: jeune, cadet   

1) Of more recent appointment or admission, as to an office or status; of lower rank or standing.
2) (in American universities, colleges, and schools) noting or pertaining to the class or year next below that of the senior
3) Younger, designating the younger of two men bearing the same full name, as a son named after his father; often written as Jr. or jr. following the name (

From L. iunior, comparative of iuvenis "young, young man," cognate with Pers. javân, → young.

Kehtar, comparative of keh "small, little," → decrease.


Fr.: Juno   

A → NASA → space mission devoted to the study of the planet → Jupiter. Juno was launched on August 5, 2011 and traveled over a total distance of roughly 2.8 billion km (1.8 → astronomical units) to reach Jupiter on July 4, 2016, after a journey of about five years. Two years after its launch Juno used a → gravity assist through an Earth → flyby in October 2013. The spacecraft will make 37 turns around Jupiter in a → polar orbit over the course of 20 months, until February 2018. Juno has nine different instruments to achieve its scientific goals. Its main goal is to understand the origin and evolution of Jupiter. Among Juno's scientific objectives, it will:
1) Determine how much water is in Jupiter's atmosphere, which helps find out which planet formation theory is correct (or if new theories are needed);
2) Look deep into Jupiter's atmosphere to measure composition, temperature, cloud motions and other properties;
3) Map Jupiter's magnetic and gravity fields, revealing the planet's deep structure;
4) Explore and study Jupiter's → magnetosphere near the planet's poles, especially the auroras, providing new insights about how the planet's enormous → magnetic field affects its atmosphere.

The spacecraft's name comes from Greco-Roman mythology. The god Jupiter drew a veil of clouds around himself to hide his mischief, but his wife, the goddess Juno, was able to peer through the clouds and see Jupiter's true nature.

Hormoz (#)

Fr.: Jupiter   

The largest → planet in the → Solar System and the fifth from the Sun, lying at a mean distance of about 5.2 → astronomical units from the Sun. Jupiter is a → gas giant, mostly → hydrogen and → helium, with a mass of 1.898 × 1027 kg, or about 0.001 → solar masses, or 318 times → Earth masses. It is more than twice as massive as all the other solar system planets combined. Jupiter's diameter measures 11 times that of Earth. Its → rotation period, 9.93 hours (Jupiter/Earth ratio = 0.41), is the shortest of all the solar system planets. Its → orbital period is 11.857 Earth years. Jupiter has an extensive family of → satellites (79 known) and a faint → ring system; → Jupiter's ring. Jupiter probably has a core of rocky material amounting to something like 10 to 15 Earth masses. Above the core lies the main bulk of the planet in the form of liquid → metallic hydrogen. This exotic form of the most common of elements is possible only at pressures about 3 million bars, as is the case in the interior of Jupiter (and Saturn). Under the extreme pressure found deep inside Jupiter, the electrons are released from the hydrogen molecules and are free to move about the interior. This causes hydrogen to behave as a metal; it becomes conducting for both heat and electricity. See also → Jupiter's atmosphere.

Jupiter "the king of ancient Roman gods, the ruler of Olympus," from L. Iupeter, from PIE *dyeu-peter- "god-father," from *deiw-os "god" (cf. Pers. div "devil, demon;" Mid.Pers. dêw; O.Pers. daiva- "evil god, demon;" Av. daēva- "evil spirit, false god;" Skt. deva-; Gk. Zeus "supreme god;" from *dei- "to gleam, to shine") + *peter "father" (cf. Pers. pedar "father;" O.Pers. pitā- "father;" Av. patar-, ptā-; Skt. pitár-; Gk. pater; L. pater, O.H.G. fater).

Hormoz, from Mid.Pers. Ohrmazd "name of the highest god in Zoroastrianism," from O.Pers. aura-mazdā-, Av. ahura-mazdā- "Wise Lord," from ahura- "lord, god;" cf. Skt. ásura- "god, lord;" Hittite hassu- "king;" M.H.G. Asen "name of a group of gods;" O.N. āss "god;" PIE *ansu- "spirit, demon" + mazdā- "wisdom," mazdāθa- "what must be borne in mind," mazdāh- "memory;" cf. Skt. medhā- "mental power, wisdom, intelligence;" Gk. mathein "to learn, to know" (root of → mathematics).

Jupiter mass
  جرم ِ هرمز   
jerm-e Hormoz

Fr.: masse de Jupiter   

A quantity of mass equal to 1.898 × 1027 kg, about 0.000954 → solar masses, or 317.83 → Earth masses. Jupiter mass, MJ, is used as a → unit to describe masses of the → gas giant, such as the outer planets and → extrasolar planets. Similarly, → brown dwarf masses are expressed in terms of Jupiter mass.

Jupiter; → mass.

Jupiter's atmosphere
  جو ِ هرمز، هواسپهر ِ ~   
javv-e Hormoz, havâsepehr-e ~

Fr.: atmosphère de Jupiter   

The gaseous envelope surrounding Jupiter. It is about 90% → hydrogen and 10% → helium (by numbers of atoms, 75/25% by mass) with traces of → methane, → water, and → ammonia. This is very close to the composition of the primordial → solar nebula from which the entire solar system was formed. Saturn has a similar composition, but Uranus and Neptune have much less hydrogen and helium. The outermost layer is composed primarily of ordinary → molecular hydrogen and helium. Visually, Jupiter is dominated by two atmospheric features; a series of ever-changing atmospheric cloud bands arranged parallel to the equator and an oval atmospheric blob called the → Great Red Spot.

Jupiter; → atmosphere.

Jupiter's ring
  حلقه‌های ِ هرمز   
halqehâ-ye Hormoz

Fr.: anneaux de Jupiter   

Any of several faint, dark, narrow rings around Jupiter. Jupiter's rings are so faint and tenuous that are only visible when viewed from behind Jupiter and are lit by the Sun, or directly viewed in the infrared where they faintly glow. Unlike → Saturn's rings full of large icy and rock chunks, they are composed of tiny rock fragments and dust. Jupiter's rings are continuously losing material and being resupplied with new dust from → meteorite impacts with Jupiter's four inner moons (→ Metis, → Adrastea, → Amalthea, and → Thebe). Jupiter's rings were discovered by NASA's Voyager 1 in 1979. They are composed of three parts: the → Main ring, a → Halo ring that orbits closer to Jupiter, and a very wide → Gossamer ring that extends far from Jupiter.

Jupiter; → ring.

Žurâsik (#)

Fr.: jurassique   

Jurassic era.

Named for the Jura Mountains on the border between France and Switzerland, where rocks of this age were first studied, + -assic, suffix extracted from Triassic.

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