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

The → Julian Date referenced to the → barycenter of the → solar system. The BJD is more precise than the → Heliocentric Julian Day because the Sun is not stationary. It moves due to the → gravitational attraction of Jupiter and the other planets.

→ barycentric; → Julian Date.

An object that seems likely to be a → black hole, but waits for more observational confirmations.

→ black; → hole; → candidate.

1) An applicant or suitable person for a position.
2) An astronomical entity which is being considered for belonging to a special class of entities; e.g. → black hole candidate, → dark matter candidate, → supernova candidate.

From L. candidatus "clothed in white" (reference to the white togas worn by those seeking office), from candidus "shining white," from candere "to shine," cf. Skt. cand- "to shine," candra "bright; the Moon;" PIE base *kand- "to glow, to shine."

Nâmzad, literally "nominated," from nâm, → name, + zad, p.p. of zadan "to strike" (Mid.Pers. zatan, žatan, O.Pers./Av. jan-, gan- "to strike, hit, smite, kill," Skt. han- "to strike, beat," Gk. theinein "to strike," L. fendere "to strike, push," Gmc *gundjo "war, battle;" PIE *g^when- "to strike, kill").

A hypothetical physical entity capable of accounting for the corresponding observed phenomena involving → dark matter. → Non-baryonic dark matter candidates include → WIMPs, → neutralinos, → axions, → gravitinos. Among → baryonic dark matter candidates can be noted ordinary and heavy → neutrinos, clouds of → neutral hydrogen gas, and compact objects.

→ dark; → matter; → candidate.

A particular day, month, and year at which some event happened or will happen.

Date, from O.Fr. date, from M.L. data, from datus "given," p.p. of dare "to give, grant, offer," from PIE base *do- "to give" (cf. Pers. dâdan "to give," as below). The Roman convention of closing a document by writing "given" and the day and month (meaning "given to messenger") led to data becoming a term for "the time stated."

Gâhdâd, from gâh "time" (Mid.Pers. gâh, gâs "time;" O.Pers. gāθu-; Av. gātav-, gātu- "place, throne, spot;" cf. Skt. gâtu- "going, motion; free space for moving; place of abode;" PIE *gwem- "to go, come") + dâd "given," as in Latin; p.p. of dâdan "to give" (Mid.Pers. dâdan "to give," O.Pers./Av. dā- "to give, grant, yield," Av. dadāiti "he gives," Skt. dadáti "he gives," Gk. didomi "I give;" akin to L. data, as above); cf. Mid.Pers., Mod.Pers. dâd "year, age, period of life," Lori, Laki dâ(d) "age," homdâ "of equal age."
Note: In current Persian a single term, târix (تاریخ), is used for two different but related concepts: date and history. This may be confusing, → history (تاریخ).

Biology: To impregnate, to fertilize.

L. fecundetus "made fruitful, fertilized," p.p. of fcundare, from fecundus "fruitful, fertile, productive," from L. root *fe-, corresponding to PIE *dhe(i)- "to suck, suckle;" cf. Skt. dhayati "sucks," dhayah "nourishing;" Gk. thele "mother's breast, nipple," thelys "female, fruitful;" Mid.Pers. dâyag "(wet-)nurse;" Mod.Pers. dâyé "(wet-)nurse;" Proto-Iranian *daH- "to suck, suckle;" O.C.S. dojiti "to suckle," dojilica "nurse;" Lith. dele "leech;" Goth. daddjan "to suckle;" O.H.G. tila "female breast."

Gošnidan, from gošn "male," Mid.Pers. gušn; cf. Av. varšni- "male;" Skt. vrsan-.

The number and fraction of → mean sidereal days elapsed on the → Greenwich meridian since 12h January 1, 4773 BC (mean sidereal).

→ Greenwich meridian; → sidereal; → date.

The → Julian Date referenced to the center of the → Sun. Since the Earth revolves around the Sun, and since light travels at a finite speed, observations of a given object taken at different positions in the Earth's orbit are not equivalent, and so a correction for Earth's orbit around the Sun is required. Left uncorrected, the time of an observational event measured by Earth clocks will vary by 16.6 minute over the course of a year. If not properly accounted for, this can lead to a spurious signal in a → periodogram.

→ heliocentric; → Julian Date.

An imaginary line following approximately the 180th meridian which, by international agreement in 1884, marks the beginning or or end of a day. The regions to the east of which are counted as being one day earlier in their calendar dates than the regions to the west.

→ international; → date; → line.

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.

A modification of the Julian Date, representing the number of days that have elapsed since midnight (instead of noon) at the beginning of Wednesday November 17, 1858. MJD = JD - 2,400,000.5 The reason for adopting that date is the fact that the Julian Day 2,400,000 just happens to be November 17, 1858.

→ modify; → Julian date.

A star which according to observational data could become a supernova.

→ supernova; → candidate.