supernova light curve
xam-e nur-e abarnovâ, ~ ~ abar-now-axtar
Fr.: courbe de lumière de supernova
The graph of luminosity as a function of time after a → supernova explosion. The → light curve goes up rapidly to a → peak luminosity, then decays away slowly over time, with different rates, depending on the → supernova type. The temporal evolution of a supernova's luminosity contains important information on the physical processes driving the explosion. The observed → bolometric light curves provide a measure of the total output of converted radiation of → Type Ia supernovae, and hence serve as a crucial link to theoretical models of the explosion and evolution.
Fr.: progéniteur de supernova
A star which is at the origin of a supernova phenomenon.
supernova remnant (SNR)
Fr.: reste de supernova
The body of expanding gas ejected at a speed of about 10,000 km s-1 by a → supernova explosion, observed as a diffuse → gaseous nebula, often with a → shell-like structure. Supernova remnants are generally powerful → radio sources. The evolution of the SNR can be divided into different phases according to the dominant physical processes. Simplified models are made for the first stages, to get an idea of typical time scales, expansion velocities, and sizes. The three main phases are: 1) the → free expansion phase, 2) the → Sedov-Taylor phase, and 3) the → snowplow phase.
šok de abar-now-axtar, toš-e ~
Fr.: choc de supernova
A → shock wave that forms when the inner → iron core (of ~ 0.5 Msun) → collapses until it reaches densities in excess of → nuclear density. At this point the pressure rises dramatically and resists further collapse. The homologous core bounces and drives out a shock wave that works its way through the remainder of the initial iron core. The small compressibility of nuclear matter halts the infall of the innermost core by an elastic collective bounce whose kinetic energy is almost immediately depleted by the → photodisintegration of heavy nuclei and the emission of → neutrinos.
Fr.: types de supernova
The classification of supernovae according to the presence or absence of the absorption lines of different chemical elements that appear in their spectra shortly after their explosion. Basically, supernovae come in two main types: those that have hydrogen (Type II, from a very massive star that blows up) and those that do not (Type I, due to thermonuclear runaways in a less massive star). Both types exhibit a wide variety of subclasses. Type Ia lacks hydrogen and presents a singly-ionized silicon (Si II) line at 6150 Å, near peak light. Type Ib has non-ionized helium (He I) line at 5876 Å, and no strong silicon absorption feature near 6150 Å. Type Ic shows weak or no helium lines and no strong silicon absorption feature near 6150 Å. Type II stars also have various subclasses. See also → Type I supernova, → Type Ia supernova, → Type Ib supernova, → Type Ic supernova, → Type II supernova, → Type II-L supernova, → Type II-n supernova, and → Type II-P supernova
Exceeding the usual or prescribed number; extra; additional.
Fr.: arc-en-ciel surnuméraire
1) The act of placing upon; the state of being placed upon.
Barhamneheš, from bar- "on, upon, up" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + -ham- "together, with," → syn-, + neheš, → position.
Fr.: principe de superposition
1) Math.: The principle concerned with homogeneous and
non-homogeneous → linear differential equations,
stating that two or more solutions to a linear equation or set of linear equations can be added
together so that their sum is also a solution.
The process whereby the amount of → water vapor in the air exceeds that needed to → saturate. In other words, the condition of air in which the → humidity is above the level required for saturation at a given temperature (i.e. the → relative humidity is greater than 100%). When the temperature drops below freezing, this can lead to a situation where more water vapor is present in the air than the air can hold. At every temperature, there is a maximum amount of water vapor that can be supported in the air. The higher the temperature, the more water vapor can be accommodated. But if the air that is already at 100% relative humidity is cooled then it becomes supersaturated, and this situation is unstable. As a result, the excess water vapor crystallizes out, either into water droplets or directly into ice.
Fr.: indice supérieur
An → index (a digit or symbol) written slightly above and to the right of a letter, such as for representing variable components in → tensor analysis. → subscript. The most common mathematical superscript is an → exponent. Other common superscripts are the single and double prime marks indicating the → first derivative and → second derivative of a → function. See also → contravariant tensor.
A class of theories that seek to unify the four fundamental forces of nature. It proposes symmetrical relationships linking fermions and bosons (particles of half integer spin, like electrons, protons, and neutrinos) with particles of integral spin (like photons and gluons).
Fr.: galaxie supermince
A galaxy that appears as an extraordinary thin and long figure on the sky because of its → edge-on orientation, highly flattened stellar → disk, and absence of a → bulge component. Superthin galaxies are → gas-rich and have optically diffuse disks with little internal absorption, as well as low emission-line intensity ratios and slowly rising → rotation curves. They seem to be among the least evolved disk galaxies in the local Universe, having undergone only minimal dynamical heating, → star formation, and → angular momentum transport. Examples are: UGC 7321, UGC 3697, UGC 9242.
A galactic-scale wind driven by the collective effect of a large number of → supernovae and → winds from → massive stars occurring in the central region of a galaxy. Superwinds have been invoked, among other things, as the source by which the → intergalactic medium is provided with → enriched gas (see, e.g. Heckman et al. 1990, ApJS 74, 833).
Fr.: galaxie à super-vent
A galaxy with → superwind characteristics. M 82 and NGC 4666 are among superwind galaxy candidates.
damâ-ye ruyé, ~ ruye-yi
Fr.: température de surface
1) For a star, same as → effective temperature.
Fr.: période synodique
For planets, the mean interval of time between two successive → conjunctions with or → oppositions to the Sun. For example, → Mars has a synodic period of 779.9 days from Earth; thus Mars' oppositions occur once roughly 2.135 years. In comparison, the synodic period of → Venus is 583.9 days. If the sideral periods of the two bodies around the third are denoted T1 and T2, their synodic period is given by: 1/Tsyn = |1/T1 - 1/T2|.
A physical quantity characterizing the mean random motion of molecules in a physical body. In other words, a measure of the average kinetic energy of the particles of a system.
From L. temperatura "a tempering, moderation," from temperatus, p.p. of temperare "to moderate, to mix." Sense of "degree of heat or cold" first recorded 1670 (Boyle), from L. temperatura, used in this sense by Galileo.
Damâ, from dam "breath of an owen; bellows; smoke; air," also "moment, time," from Mid./Mod.Pers. damidan "to blow, breathe;" Av. dāδmainya- "blowing up;" cf. Skt. dahm- "to blow," dhámati "blows;" Gk. themeros "austere, dark-looking;" Lith. dumti "to blow;" PIE dhem-/dhemə- "to smoke, to blow."
nâhamsângardi-ye damâ (#), nâ-izogardi-ye ~
Fr.: anisotropie de température
Cosmology: Minute temperature variations of the cosmic microwave background radiation.