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

A comet with a period less than 200 years. Same as → periodic comet.

→ short; → period; → comet.

A variable star that has a relatively short period with respect to stars of similar types.

→ short; → period; → variable.

1) A deficiency in quantity.
2) The amount of such → deficiency.

From → short + suffix -age.

Kambud, from kam "little, few, deficient, scarce" + bud, from budan, → exist.

Same as → Schottky noise; → shot noise.

Translation of Ger. Schroteffekt, from Schrot "small shot, buckshot" + Effekt; → effect.

Same as → Schottky noise and → shot effect.

→ shot effect.

→ Schottky noise.

The upper joint of each of a person's → arms and the part of the → body between this and the → neck.

M.E. schuldre, sholder, shulder, schulder, from O.E. sculdra, sculdor, akin to Du. schouder, Ger. Schulter.

Duš "shoulder;" Mid.Pers. dôš "shoulder;" Av. daoš- "shoulder;" cf. Skt. dós- "shoulder."
Soft "shoulder;" Mid.Pers. suft.

→ scapula.

→ shoulder; blade, M.E.; O.E. blæd "blade of grass;" cognate with Du. blad, Ger. Blatt.

Šâné, ketf, → scapula.

1) A brief, abrupt precipitation from a cloud, characterized by the suddenness with which it begins and ends and by the rapid changes in intensity.
2) An abundant flow; an outpouring, such as → cosmic-ray shower; → air shower; → meteor shower.

M.E. shour; O.E. scur "short fall of rain, fall of missiles or blows;" cf. O.N. skur, O.S., O.H.G. scur, Ger. Schauer.

Ragbâr "cloudburst," from rag "cloudburst; thunder," → rain + bâr "raining, rain," from bâridan, → rain.
Tondbâr, with tond "fast," → velocity.

A → meteor that is part of a group moving in the same orbit around the Sun. → meteor shower.

→ meteor; → shower.

1) A pair of rolling lids that are used to open or close the dome slit. Same as → dome shutter.
2) A mechanical device that controls the time during which light is admitted in an optical system.

Shutter, from shut (v.), from O.E. scyttan from W.Gmc. *skutjanan + → -er.

Bastâr, from bast, past tense stem of bastan + -âr. Bastan, from Mid.Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind," cf. Ger. binden, E. bind, → band. The suffix -âr creates agent nouns (as in xaridâr, virâstâr, foruxtâr, nemudâr, etc.).

The system of → SI units.

→ SI units.

A coherent and rationalized system of units, in common use in physics since 1969. The seven basic units are the → meter, the → kilogram, the → second, the → ampere, the → kelvin, the → mole, and the → candela. Same as international system of units.

SI, from Fr. Système Internationale d'unités; → unit.

A person's brother or sister.

M.E., from O.E. sibling "relative, kinsman," from sibb "kinship, relationship; love, friendship," cf. O.Saxon sibba, M.Du. sibbe, O.H.G. sippa, Ger. Sippe "kin, related," Icelandic sifi "related."

Barxâ, from bar- first sylaable of barâdar, → brother, + xâ-, short for xâhar (x^wâhar), → sister.
Hamšir, literally "of the same milk," more specifically "sucking the same breast." However, a hamšir may not be a person's brother or sister.

1) An implement for cutting grain, grass, etc., consisting of a curved, hooklike blade mounted in a short handle.
2) → Sickle of Leo.

M.E. sikel, O.E. sicol; cf. Du. sikkel, Ger. Sichel, ultimately from L. secula "sickle," from PIE root *sek- "to cut," → section.

Das "sickle," Mid.Pers. dâs "sickle;" variant dahre, → scythe; Wakhi δətr, Parachi dêš "sickle;" ultimately from Proto-Iranian *dāθra-; cf. Skt. dātra- "sickle, scythe."

A sickle-shaped → asterism forming the back of the Lion's head. It is marked by six stars: ε Leonis, μ Leonis, ζ Leonis, γ Leonis, η Leonis, and α Leonis (→ Regulus).

→ sickle; → Leo.

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.