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

The hour angle of the mean equinox for a given observer.

→ mean; → sidereal; → time.

A class of → meteorites that is → brecciated→ stony-iron with nearly equal amounts of → metal and → silicates.

→ meso-; → siderite.

To occupy the place of authority or control, as in an assembly or meeting; act as president or chairperson (Dictionary.com).

→ pre-; → reside.

1) The highest executive officer of a modern republic, as the Chief Executive of the United States (often initial capital letter).
2) An officer appointed or elected to preside over an organized body of persons (Dictionary.com).

→ preside; → -ent.

Farneštgâr, from farnešt, present stem of farneštidan, → preside, + agent noun suffix -gâr, → -or, on the model of âmuzgâr "teacher."

To dwell permanently or for a considerable time.

M.E., from M.Fr. resider and directly from L. residere "sit down, settle; remain behind, rest," from → re- "back, again" + sedere "to sit," cognate with Pers. nešastan "to sit down," as below.

Neštidan, from Baluci ništ-, Kurd. ništin, Gurani nîšt, Awromani ništay-, Gazi ništ, Shahmerzadi -ništ, Gilaki ništoen "to sit down," variant of Pers. nešastan "to sit down, settle down," nešim "nest," Mid.Pers. nišastan "to sit;" O.Pers. nišādayam [1 sg.impf.caus.act.] "to sit down, to establish," hadiš- "abode;" Av. nišasiiā [1 sg.subj.acr.] "I shall sit down," from nihad- "to sit down," from → ni- "down, below," + had- "to sit;" PIE base *sed- "to sit;" cf. Skt. sad- "to sit," sidati "sits;" Gk. hezomai "to sit," hedra "seat, chair;" L. sedere "to sit;" O.Ir. suide "seat, sitting;" Welsh sedd "seat;" Lith. sedmi "to sit;" Rus. sad "garden;" Goth. sitan, Ger. sitzen; E. sit.

1) The place, especially the house, in which a person lives or resides; dwelling place; home.
2) The act or fact of residing (Dictionary.com).

→ reside; → -ence.

Neštgâh, from nešt present stem of neštidan→ reside + -gâh a suffix of place and time. Neštmân with -mân a suffix of verbl nouns used with present and past stems, as in zâymân, câymân, sâxtemân, sâzmân, goftemân, râžmân.

A person who resides in a place.

→ reside + -ent, a suffix, equivalent to -ant froming nouns and adjectives.

1) A line segment that forms part of the perimeter of a plane geometric figure.
2) A surface of a solid geometric figure.

M.E., from O.E. side "flanks of a person, the long part of anything;" cf. O.S. sida, O.N. sitha, M.Du. side, O.H.G. sita, Ger. Seite.

Bar "side; breadth; breast," variant var; Mid.Pers. var "breast;" Av. vouru "wide, broad, extended" (vourucašāni- "looking far"), related to varah- "breast;" cf. Skt. urú- "wide, broad," úras- "breast;" Gk. eurus "wide, broad;" PIE base uer-, ueru-s "wide, broad."
Pahlu "side, flank;" Mid.Pers. pahlug "side, rib," Av. pərəsu- "rib," Ossetic fars "side, flank," cf. Skt. párśu- "rib," O.C.S. prbsi "breast," Lit. piršys (pl.) "horse breast."
Kenâr "side," variant karân "edge, limit;" Mid.Pers. karân, karânak, kenâr "edge, limit, boundary;" Av. karana- "side, boundary, end."
→ octagon, → polygon, → quadrilateral, → triangle.

1) In → radio astronomy, smaller amounts of gain found either side of the main lobe.
2) In transmitting antennae, radiation in any direction other than that required.

→ side; → lobe.

Either of the two bands of frequencies, one just above (upper side) and one just below (lower side) a carrier frequency, that result from modulation of a carrier wave.

→ side; → band.

Bând, → band; kenâr "side," variant karân "edge, limit;" Mid.Pers. karân, karânak, kenâr "edge, limit, boundary;" Av. karana- "side, boundary, end."

Of, relating to, or determined by or from stars.

From M.Fr. sidereal, from L. sidereus "starry, astral," from sidus (genitive sideris) "star, constellation."

Axtari, pertaining to axtar "star," probably a variant of setâré→ star.

The period of → Earth's rotation around its axis, the mean value of which is about 23h 56m 04.092s (23.934 470 hours). In other words, the interval between two successive passages of a star across a given → meridian. The sidereal day is 3 minutes 56 seconds shorter than the → mean solar day. The reason is that Earth moves a little less than a degree around the Sun during the time it takes for one full axial rotation. So, for the Sun to appear on the same meridian in the sky again after one full axial rotation, the Earth has to rotate one extra degree to bring the Sun into the same apparent meridian in the sky. This is also why the stars rise and set about 4 min earlier each day.

→ sidereal; → day.

The angle on the celestial sphere measured westward from the hour circle of the vernal equinox to that of the celestial body.

→ sidereal; → hour angle.

The time taken by the Moon to complete one → revolution around the Earth with respect to a background, → fixed star. The average time is 27.321 661 days (27d 7h 43m 11.5s). Same as → lunar sidereal orbital period.

→ sidereal; → month.

→ sidereal revolution period; → sidereal rotation period.

→ sidereal; → period.

The time taken by a planet or satellite to complete one revolution about its primary with respect to stars. For Earth, same as → sidereal year. Sidereal periods of the solar system planets, interms of the sidereal year, are as follows: Mercury 0.240846 (87.9691 days); Venus 0.615 (225 days); Earth 1 (365.25636 solar days); Mars 1.881; Jupiter 11.86; Satrurn 29.46; Uranus 84.01; and Neptune 164.8. That of the Moon is 0.0748 (27.32 days) and for → Sedna 12050.

→ sidereal; → revolution; → period.

The rotation period of a celestial body with respect to fixed stars. For Earth, same as → sidereal day.

→ sidereal; → rotation; → period.

The time based upon → Earth's rotation with respect to the stars, with the → sidereal day as the unit of measurement. At the moment when the → vernal equinox crosses the → meridian in → upper culmination, sidereal time is equal to zero hours for that observing position. The → hour angle of the vernal equinox is equal to sidereal time.

→ sidereal; → time.

The interval between two successive passages of the Sun, in its apparent → annual motion around the → celestial sphere, through a particular point relative to stars. It is equal to 365.256356 days for the J2000.0 epoch and is 20m 24.5s longer than the → tropical year.

→ sidereal; → year.

1) A mineral composed of iron carbonate, FeCO₃, that is a valuable ore of → iron.
2) A category of → meteorites consisting mainly of → iron and → nickel, commonly referred to as Irons. There are 13 different chemical groups of siderites. These groups are defined based on the relative abundance of nickel, gallium, germanium, and iridium. Irons are also categorized by their structural type.

→ sidero-; → -ite.