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

→ comet nucleus.

→ cometary; → nucleus.

The → path followed by a → comet in the → solar system around the → Sun. Most cometary orbits appear to be → elliptical, or in some cases → parabolic. The orbits of → short-period comets are elliptical, carrying them out to a region lying from → Jupiter to beyond the orbit of → Neptune. Those of → long-period comets are very elliptical. The orbits may be strongly influenced if they pass near the Jovian planets, particularly Jupiter itself. The cometary orbits are also influenced to some degree by gases shooting out of comets, so their orbits are primarily but not completely determined by gravity. Newton (1644-1727) was the first to compute a cometary orbit. He found that the comet of 1680 was following a parabolic orbit around the Sun. Edmond Halley (1656-1742), following the methods of Newton, computed the → orbital elements of 24 comets. He realized that the comets of 1531, 1607 and 1682 had very similar elements and postulated that they were in fact the same object, orbiting an elongated ellipse. He predicted the next return to occur in 1758 or early 1759. The return of what is now called Halley's comet was observed after his death, This first observation of a "predicted" comet is manifestly one of the major successes of → celestial mechanics.

→ cometary; → orbit.

A formation of → gas and/or → dust that streams away from the → coma of many comets under the influence of the Sun's → radiation pressure and the → solar wind. See also: → dust tail, → gas tail, → ion tail, → plasma tail, → sodium tail, → Type I tail, → Type II tail, → antitail.

→ cometary; → tail.

(adj.) Of the same size, extent, or duration as another; proportionate.

L.L. commensuratus, from → com- "together, with" + mensuratus, p.p. of mensurare "to measure," from menusra "measure."

Hammasâ, from ham- "together," → com- + masâ "size, greatness," from Mid.Pers. masây, masâk "size," Av. masah- "size, greatness, length," maz-, masan-, mazant- "great, important," mazan- "greatness, majesty," mazišta- "greatest," cf. Skt. mah-, mahant-, Gk. megas, L. magnus; PIE *meg- "great."

Of two bodies orbiting around a common barycenter, when the orbital period of one is an exact fraction, for example one-half or two-thirds, of the other.

→ commensurate; → orbit.

1a) A remark, observation, or criticism (Dictionary.com).
1b) A note in explanation, expansion, or criticism of a passage in a book, article, or the like; annotation (Dictionary.com).
2) To make remarks, observations, or criticisms (Dictionary.com).

M.E. coment, from O.Fr. coment "commentary;" L.L. commentum "comment, interpretation," in classical L. "invention, fiction," from comminisci "to contrive, devise," from → com-, intensive prefix + base of meminisse "to remember," related to mens, → mind.

Hâmat, from hâ-, intensive prefix, variant of ham-, → com-, + mat- "think; thought," from Av. mat- matay- "to think," humat- "good thought;" cf. Skt. matāy-.

1) A series of comments, explanations, or annotations (Dictionary.com).
2) An explanatory essay or treatise (Dictionary.com).

From M.E. commentaries (plural), from L. commentarium "notebook," noun use of neuter of commentarius, from comment(um), → comment, + -arium, → -ary.

Hâmatgân, from hâmat, → comment, + gân suffix forming plural entities, from Mid.Pers. -gânag, -gâna.

To deliver, to write a → commentary on.

Verb from → comment.

1) A person who makes commentaries.
2) A person who discusses news, sports events, weather, or the like, as on television or radio.

Agent noun from → commentate.

Putting a telescope or an observing instrument into active service after their final construction.

From L. commissionem "delegation of business," from commissus, p.p. of committere "to bring together," from → com- "together" + mittere "to put, send."

Râhandâzeš, verbal noun from compound verb râhandâxtan "to set in work; to prepare," from râh "way, path" + andâxtan "to cast; to make, do; to throw."

A period during which a newly constructed observing instrument is used for test.

→ commissioning; → period.

Belonging to or shared by two or more or all in question. → common denominator, → least common multiplier.

From M.E. comun, from O.Fr. comun, from L. communis "in common, public, general, shared by all or many," originally "sharing common duties," akin to munia "duties, public duties, functions," from munus "task, duty, gift."

Hamdâr, literally "possessing together, sharing together," from ham-, → com-, + dâr present stem of dâštan "to have, to possess," from Mid.Pers. dâštan, O.Pers./Av. root dar- "to hold, keep back, maitain, keep in mind," Skt. dhr-, dharma- "law," Gk. thronos "elevated seat, throne," L. firmus "firm, stable," Lith. daryti "to make," PIE *dher- "to hold, support."

A quantity into which all the denominators of a set of fractions may be divided without a remainder.

→ common; → denominator.

A fraction written as a/b where a and b are → positive  → integers, as opposed to a → decimal fraction; for example, 5/7. Common fractions are sometimes also called → vulgar fractions.

→ common; → fraction.

The logarithm with → base 10. It is known also as the → decimal logarithm, decadic logarithm, or Briggsian logarithm, after Henry Briggs, an English mathematician who pioneered its use.

→ common; → logarithm; → decimal.

A calendar year which is not a → leap year. In the → Gregorian calendar, a year with 365 days divided into 12 → months, and only 28 days in February. In the → Iranian calendar, a year consisting of 365 days with 12 months, and only 29 days in the month of Esfand.

→ common; → year.

The ordinary people, as distinguished from those with authority, rank, station, etc.; the common people. Also, commonality (Dictionary.com).

M.E., from M.Fr. comunalte, from comunal- "communal," → common, + -te "-ty," a suffix denoting state, quality, etc.

Mid.Pers. pâtram "common people, commonalty" (MacKenzie), variant pâyram, prefixed from ram "herd, flock," Mod.Pers. ramé "herd, flock."

The fact or state of being → common or happening often.

→ common; → -ness.

1) A small group of persons living together, sharing possessions, work, income, etc., and often pursuing unconventional lifestyles.
2) Any community organized for the protection and promotion of local interests, and subordinate to the state (Dictionary.com).

From M.Fr. commune "free city, group of citizens," from M.L. communia, noun use of neuter plural of L. adj. communis, literally "that which is common," from communis, → common.

Hamdâré, from hamdâr, → common.

1a) To impart knowledge of; make known.
1b) To give to another; impart; transmit (as a disease).
2a) To give or interchange thoughts, feelings, information, or the like, by writing, speaking, etc.
2b) To express thoughts, feelings, or information easily or effectively (Dictionary.com).

From L. communicatus, p.p. of communicare "to share, divide out; impart; inform; join, participate in," literally "to make common," from communis, → common.

Hamdârgandan, literally "to diffuse to the public," from hamdâr, → common, + gan, variant kan "to throw, diffuse" (as in parâgan-, parâgandan "to diffuse, disperse, scatter;" afgandan "to throw; to lay, place;" kandan "to dig; to extract"), from Proto-Ir. *kan- "to throw, place, put, disperse, → scatter" + -dan infinitive suffix.