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

1) In a → star cluster, coming across of two stars so closely that their → orbits alter by their mutual → gravitational attractions.
2) As regards an → asteroid or → comet, a situation when it crosses the Moon's orbit and approaches the Earth with a risk of collision. See also → close approach, → encounter.

→ close; → encounter.

Generally,a device for indicating a number or amount.
Any of various instruments for detecting ionizing radiation and for registering counts. → Geiger counter.

M.E. countour, from O.Fr. conteor, from L. computator, from computa(re) "to compute" + → -tor suffix forming personal agent nouns mainly from verbs.

Šomârgar, from šomâr present tense stem of šomârdan "to count," → count + agent suffix -gar.

A prefix used with the meanings "against, contrary, opposite." → contra-.

M.E. countre-, from O.Fr. contre-, from L. contra "opposite, against;" PIE base *kom- "beside, near, by, with."

Pâd- "contrary to; against; opposing," variants pâ- (pâsox, pâzahr, pâhang, → response), paž- (pažvâk, → echo, pažâvand "the bar of a door or a gate, door lock"), baž- (bažkam, → forbidden), pat- (patvâz, → correspond), pa- (panâh, padid), from Mid.Pers. pât-, from O.Pers. paity "agaist, back, opposite to, toward, face to face, in front of," Av. paiti, akin to Skt. práti "toward, against, again, back, in return, opposite," Pali pati-, Gk. proti, pros "face to face with, toward, in addition to, near;" PIE *proti.

An equal weight, power, or influence acting in opposition.

→ counter-; → balance.

In a direction opposite to the rotating hands of a clock.

From counter- "contrary; opposite; opposing," + → clockwise.

Pâdsâ'atsu, from pâd-, → counter-, + sâ'atsu, → clockwise.

Logic: An individual case or instance that falsifies a universal generalization. A counterexample to an → argument is a situation in which the → premises are → true, but the → conclusion is → false. For example, "All dogs are mammals" (true). "All cats are mammals" (true). "Therefore, all cats are dogs." (false).

→ counter-; → example.

The movement of a fluid in the opposite direction to a fluid flowing in the same cross section of a turbulent medium.

→ counter-; → flow.

Same as → gegenschein.

A person or thing that corresponds to or has the same function as another person or thing in a different place or situation (OxfordDictionaries.com).
→ electromagnetic counterpart, → optical counterpart, → radio counterpart.

M.E., from O.Fr. contrepartie, from contre "facing, opposite," → counter-, + partie "copy of a person or thing," originally feminine p.p. of partir "to divide."

Hamtâ "counterpart, resembling, equal," from ham- "together, with; same, equally, even," → com-, + tâ "fold, plait, ply; piece, part," also a multiplicative suffix; Mid.Pers. tâg "piece, part."

A weight that balances another weight.

→ counter-; → weight.

Pârsang "a make-weight," from pâr-, a variant of pâd-, → counter-, + sang a variant of sanj, sanjidan "to measure; compare, put in balance," → object; alternatively, pârsang "a piece of stone," from pâr, short for pâré "piece, part," + sang, → stone, meaning "weight."

An → electromagnetic signal associated with the location on the sky and the time of a → gravitational wave event. The electromagnetic signal is predicted by models to be associated with the → merger of a → compact binary star system composed of two → neutron stars (NS) or a neutron star and a → black hole (BH). Accordingly, the gravitational waves are accompanied by a short-duration → gamma-ray burst (GRB) powered by the → accretion of material that remains in a → centrifugally supported → torus around the BH following the merger. NS-NS/BH-NS mergers are also predicted to be accompanied by a more isotropic counterpart, commonly known as a → kilonova. Kilonovae are day to week-long thermal, → supernova-like → transients, and are powered by the → radioactive decay of heavy, neutron-rich elements synthesized by the → r-process in the expanding merger ejecta (Li and Paczynski 1998). The first detection of an electromagnetic counterpart to gravitational waves belongs to → GW170817.

→ electromagnetic; → counterpart.

General: A meeting, especially one that is unplanned, unexpected, or brief. An often violent meeting; a clash.
Coming across of two bodies (as two stars in a cluster) which results in the deviation from original directions of motion. → close encounter; → strong encounter; → weak encounter.

From O.Fr. encountrer "confront," from encontre "against, counter to," from L.L. incontra "in front of," from L. in- "in" + contra "against."

Ruyâruyi "being face to face," from ru, ruy "face, countenance," variant rox (Mid.Pers. rôy, rôdh "face," Av. raoδa- "growth," in plural "appearance," from raod- "to grow, sprout, shoot," cf. Skt. róha- "rising, height") + euphonic interfix -â- + ruy + noun suffix -i.

A device for detecting ionizing radiations, whether corpuscular (α-, β-particles), or electromagnetic (X- and gamma-rays). It consists essentially of a fine wire anode (e.g., tungsten) surrounded by a coaxial cylindrical metal cathode, mounted in a glass envelope containing gas at low pressure. A large potential difference (800 to 2000 volts) is maintained between the anode and the cathode. The ionizing particle can enter through a thin glass or mica window. The particle produces ionization of gas molecules. The ions are accelerated by the electric field and produce more ions by collisions, causing the ionization current to build up rapidly. The current, however, decays quickly since the circuit has a small time constant. There is therefore a momentary potential surge which may be amplified and made to actuate a relay to advance a mechanical counter, or to produce a click in a loudspeaker. Same as Geiger-Mulle counter.

Named after Hans Geiger (1882-1945), the German physicist, who invented the instrument. He is also known for his work on atomic theory and cosmic rays; → counter.

An encounter in which two moving bodies alter each other's direction and velocity by mutual → gravitational attraction.

→ gravitational; → encounter.

An astronomical object with usually weak emission in the → visible found to be the optical representation of the object radiating chiefly in other → wavelengths of the → electromagnetic spectrum.

→ optical; → counterpart.

A device in which an electronic detection system receives pulses that are proportional to the number of ions formed in a gas-filled tube by ionizing radiation.

→ proportional; → counter.

A device that records counts the total number of pulses received over a given time interval.

→ pulse; → counter.

The representation in → radio wavelengths of an astronomical object that has emission in other parts of the → electromagnetic spectrum.

→ radio; → counterpart.

A device for detecting and measuring ionizing radiation by means of flashes produced when the radiation particles strike a sensitive layer of phosphor.

→ scintillation; → counter.

In a star cluster, a → close encounter that strongly changes a star's velocity.

→ strong; → encounter.