pulsational pair-instability supernova
abar-now-axtar-e nâpâydâri-ye tapeši-ye joft
Fr.: supernova à instabilité pulsationnelle de paires
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.
1) In the → eye, the apparently black opening in the center of the
→ iris that permits light to pass and be focused on the
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.
Fr.: masquage de pupille
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.
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
Fr.: Puppis A
A → supernova remnant in the constellation → Puppis, and one of the brightest sources in the X-ray sky. The → supernova occurred about 4000 years ago at a distance of about 6,000 light-years. Also called SNR G260.4-03.4. Its X-ray designation is 2U 0821-42.
cahârtâ (#), cahârtâyi (#)
Fourfold; consisting of four parts.
M.E. from L. quadruplus, from quadru- + duple, from duplus, from du(o) "two" + -plus "fold."
Cahârtâ, from cahâr, → four, cognate with L. quattuor, + tâ "fold, plait, ply; piece, part" (Mid.Pers. tâg "piece, part").
Fr.: système quadruple
A stellar system consisting of four stars orbiting around a common → center of mass.
cahârqotbé (#), cahârqotbe-yi (#)
A set of either two → electric dipoles or two → magnetic dipoles in close proximity to each other arranged with alternating polarities and acting as a single unit. Quadrupole interactions are much smaller than dipole interactions, but can allow transitions forbidden in dipole moment transitions.
Fr.: anisotropie quadrupolaire
The → anisotropy which is at the origin of the → cosmic microwave background polarization. The quadrupole anisotropy could arise from three types of perturbations: → scalar perturbation, → vector perturbation, and → tensor perturbation
Fr.: lentille quadrupôle
Fr.: moment quadrupolaire
A quantity characterizing an electric charge distribution, determined by the product of the charge density, the second power of the distance from the origin, and a spherical harmonic over the charge distribution.
Fr.: amas du quintuplet
A bright → open cluster of stars located within 100 light-years of the center of the Milky Way Galaxy, and one of the three → Galactic center clusters. The Quintuplet cluster was originally noted for its five very bright stars, but it is now known to contain many luminous → massive stars that are not detected at visible wavelengths due to heavy extinction by dust along the line of sight. The cluster is about 4 million years old and had an initial mass over 104 solar masses. The five brighter stars of the cluster are dusty → WC Wolf-Rayet stars. The Quintuplet cluster also contains two → Luminous Blue Variables, the Pistol star and FMM362. The Pistol star has a luminosity 107 times solar making it one of the most luminous stars known. The Quintuplet cluster is more dispersed than the nearby → Arches cluster.
Quintuplet, from the five brightest stars originally observed; → cluster.
abarqul-e sorx (#)
Fr.: supergéante rouge
A supergiant star with spectral type K or M. Red supergiants are the largest stars in the Universe, but not necessarily the most massive. Betelgeuse and Antares are the best known examples of a red supergiant.
pâregi (#) , gosast (#)
From L. ruptura "the breaking (of an arm or leg), fracture," from p.p. of rumpere "to break."
jofteš-e Russell-Saunders, jafsari-ye ~
Fr.: couplage Russell-Saunders
A coupling scheme of → electron configuration, used mainly for the lighter atoms with → atomic number less than 30. In an atom when changes in energy states are produced by the action of two or more electrons, the value of the total angular momentum of these electrons results from the coupling between the total → orbital angular momenta of the electrons and the total → spin angular momenta of the electrons. In this scheme the orbital angular momenta and spin angular momenta of electrons are added separately to give the total angular momentum L = Σi li and the total electron spin angular momentum S = Σi si. These are then added to give J = L + S. Also called → LS coupling. See also → jj coupling.
After Henry Norris Russell (1877-1957) and Frederick Albert Saunders (1875-1963), American astronomers (1925, ApJ 61, 38); → coupling.
In computer science, to increase the processing power of the same node/system by increasing its resources (CPU, RAM, etc.). This is a type of → vertical scaling opposite to → scale down. For example, instead of a machine with a CPU running at speed of X and having Y gigabytes of memory, use a machine with a CPU running at speed of 4X and a memory of 4Y gigabytes. See also → scale in, → scale out.
Fr.: groupe du Sculpteur
The nearest group of galaxies to our → Local Group, lying near the south Galactic pole at about 10 million → light-years distance. The Sculptor Group is dominated by five galaxies, four spiral (NGC 247, 253, 300, and 7793) and one irregular (NGC 55). The brightest of the five is NGC 253. The nearest galaxy in this group is NGC 55 which at a distance of 5 million light-years lies on the border of the Local Group.
Fr.: deuxième dragage
A → dredge-up process that occurs after core helium burning, in which the convective envelope penetrates much more deeply, pushing hydrogen burning shell into close proximity with the helium burning shell (→ first dredge-up). This arrangement is unstable and leads to burning pulses. The reason is that the hydrogen shell burns out until there is enough helium for the helium combustion to occur and all the helium is rapidly burnt. Afterward the hydrogen shell again burns outward and the process repeats.
From sextuple, from L. sext(us) "sixth," → six, + et