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

Same as → plerion.

→ pulsar; → wind; → nebula.

To expand and contract rhythmically.

Verb from → pulse.

A type of → variable star that changes its brightness by changing its volume through expansion and contraction. Classical pulsating stars, including → Cepheids, → RR Lyrae, and → Delta Scuti variables, are located in a quite narrow almost vertical region in the → H-R diagram, known as → instability strip. See also → kappa mechanism.

Pulsating, verbal adj. of → pulsate; → star.

Same as → oscillating Universe.

Pulsating, verbal adj. of → pulsate; → universe.

The act of pulsating; beating or throbbing; vibration or undulation. → stellar pulsation.

Verbal noun of → pulse.

The way in which pulsations occur in a star due to the fact that stars act as resonant cavities, as studied in → asteroseismology. A star may pulsate either with approximately spherical symmetry (radial pulsation), or as a series of waves running across the surface (non-radial pulsation). Pulsation may occur in a single mode or in multiple modes, depending on the type of star. Three different modes of pulsations have been detected through the → helioseismology of the → Sun: → p mode, → g mode, and → f mode, generated by acoustic, gravity, and surface gravity waves respectively. Also called → oscillation mode.

→ pulsation; → mode.

Of or pertaining to → pulsation. → pulsational instability; → pulsational pair-instability supernova.

→ pulsation; → -al

A term used to describe irregularly spaced, fine-scale structure in optically thick rings. The process relies on a combination of viscosity and self-gravity of ring material to produce this fine structure. Also known as overstability (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ pulsational; → instability.

A → supernova resulting from the → pair instability that generates several successive explosions. According to models, a first pulse ejects many solar masses of hydrogen layers as a shell. After the first explosion, the remaining core contracts and searches for a stable burning state. When the next explosion occurs a few years later, several solar masses of material are again ejected, which collide with the earlier ejecta. This collision can radiate 10⁵⁰ erg of light, about a factor of ten more than an ordinary → core-collapse supernova. After each pulse, the remaining core contracts, radiates neutrinos and light, and searches again for a stable burning state. Later ejections have lower mass, but have higher energy. They quickly catch up with the first shell, where the collision dissipates most of their kinetic energy as radiation. The first SNe from → Population III stars are likely due to pulsational pair instability (Woosley et al. 2007, Nature 450, 390). See also → pair-instability supernova.

→ pulsational; → pair; → instability.

1) Something that pulsates or beats.
2) A → pulsating star. See also → hybrid pulsator.

→ pulsator; → -or.

1a) (v.) To → beat, to → vibrate.
1b) (v.) Physics: To → emit  → particles or → radiation  → periodically in short → bursts.
2a) (n.) Physics: A variation of a quantity whose value is normally constant. The essential characteristics of a pulse are: a → rise, a finite → duration, and a → decay.
2b) (n.) Physics: A single, abrupt emission of particles or radiation. See also → pulse counter, → pulse nulling, → pulse width, → pulsed laser, → precursor pulse.

M.E., from M.Fr. pous, from L. pulsus "a beat," p.p. of pellere "to push, drive," from PIE *pel- "to shake, swing."

Tapidan "to beat, throb," Mid.Pers. tapīdan "to be anguished; to suffer; to grow hot, to be hot," variant tâftan, tâpidan "to stir up, to excite; to shine;" tâp "fever;" Av. tap- "to be hot, to grow hot," tafnah-, tafnu- "fever, feverish heat;" cf. Skt. tap- "to spoil, injure, damage,; to suffer; to give out heat, to be hot," tápati; L. tepere "to be warm;" PIE base *tep- "warm."

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

→ pulse; → counter.

A phenomenon seen in the → radio  → emission of many → pulsars where the emission appears to cease, or is greatly diminished, for a certain number of pulse periods. Typical time scales of nulling are of the order of a few pulse periods, however it may last for up to many hours in certain pulsars. For example, PSR B0826-34 is active for only about 20% of the time. Same as → pulsar nulling.

→ pulse + verbal noun of → null.

The interval of time between two successive pulses. Also called pulse length, pulse duration.

→ pulse; → width.

A laser that emits short pulses of coherent light in fixed intervals, rather than a continuous flow of photons. → laser; → high power laser.

Pulsed adj. of → pulse; → laser.

To raise, drive, supply or inject as if by using a pump.

From M.E. pumpe, from M.Du. pompe "water conduit, pipe," or M.L.G. pumpe "pump."

Pompidan infinitive, from pomp, loan from Fr. pompe

The act or process of pumping. → optical pumping.

Verbal noun of → pump.

1) In the → eye, the apparently black opening in the center of the → iris that permits light to pass and be focused on the → retina.
2) In a → lens, the → image of the → aperture stop as seen from → object and → image space. Same as → entrance pupil.

From M.E. pupille, from O.Fr. pupille, from L. pupilla, originally "little girl-doll," diminutive of pupa "girl, doll" (Fr. poupée), so called from the tiny image one sees of himself reflected in the eye of another.

Mardomak "little man," the allusion being to the tiny image of himself reflected in the eye of another, from mardom "man, human being, mankind, people;" → people, + diminutive suffix -ak.

A method for reaching the → diffraction-limited  → angular resolution of a monolithic telescope by using an → interferometric technique. A mask with several small openings is placed in the telescope pupil plane or in a conjugated plane so as to only pass light from selected regions, thus transforming the telescope into an array of small subapertures without redundancy. When the light from each of these separate subapertures is combined, → interference fringes are formed which encode information on the spatial structure of the source (Haniff et al. 1987, Nature 328, 694). Coupled with a novel technique which filters the → atmospheric turbulence through fibers, pupil masking allows reaching a high dynamic range (Perrin et al. 2006, MNRAS 373, 747), which is necessary for detecting very faint objects, such as → exoplanets, adjacent to bright stars.

→ pupil; → masking.

The Stern. One of the larger constellations of the southern hemisphere representing the stern of the ship Argo Navis, located at 7h 30m right ascension, 40° south declination. Its brightest star is → Naos. Abbreviation: Pup; genitive: Puppis.

From L. puppis "stern, poop, the rear, or aft part of a ship or boat."

Pasâl, from pas "behind" (e.g.: pas-e pardé "behind the curtain"), variant pošt "back; the back; behind" (Mid.Pers. pas "behind, before, after;" O.Pers. pasā "after;" Av. pasca "behind (of space); then, afterward (of time);" cf. Skt. paścā "behind, after, later;" L. post, as above; O.C.S. po "behind, after;" Lith. pas "at, by;" PIE *pos-, *posko-) + -âl, → -al. → prow = farâl (فرال).