The process by which a liquid or a gas is cooled below the temperature at which a → phase transition should occur. For example, water can be cooled well below the → freezing point without freezing (as often happens in the upper atmosphere). The introduction of an → impurity or surface can trigger freezing.
1) Thermodynamics: Describing a condition in which a substance has
a temperature or pressure above its critical value of temperature or pressure.
Fr.: fluide supercritique
A fluid that is at a temperature and pressure above its thermodynamic critical point. In these conditions the substance acquires unique characteristics of density and mobility. Supercritical fluids exist deep inside some planets; for example, there is supercritical water deep inside the Earth.
A → fluid that exhibits frictionless flow, very high heat → conductivity, and other unusual physical properties. For example, → liquid helium at the temperature about 2.17 K (→ lambda point) becomes a zero → viscosity fluid which will move rapidly through any pore in the apparatus. See also → helium II.
supergalactic coordinate system
râžmân-e hamârâhâ-ye abarkahkašâni
Fr.: système des coordonnées supergalactiques
A spherical → coordinate system in which the → equator is the → supergalactic plane. Supergalactic longitude, SGL, is measured → counterclockwise from direction l = 137.37 deg, b = 0 deg (between 0 and 360 deg). The zero point for supergalactic longitude is defined by the intersection of this plane with the → Galactic plane. In the → equatorial coordinate system (J2000) this is approximately 2.82 h, +59.5 deg. Supergalactic latitude, SGB, is measured from the supergalactic plane, positive northward and negative southward. The North Supergalactic Pole (SGB=90 deg) lies at galactic coordinates l = 47.37 deg, b = +6.32 degrees, corresponding to the equatorial coordinate system (J2000) 18.9 h, +15.7 deg.
Fr.: latitude supergalactique
Fr.: longitude supergalactique
Fr.: plan supergalactique
The symmetry plane of the → Local Supercluster, where density of galaxies in our environment is the largest. The plane passes through the → Virgo cluster of galaxies, about which many of the brightest galaxies in the sky are concentrated. The supergalactic plane was recognized by Gérard de Vaucouleurs (1918-1995) in 1953 from the → Shapley-Ames catalogue.
supergiant B[e] star (sgB[e])
setâre-ye B[e]-ye abarqul
Fr.: étoile B[e] supergéante
A highly luminous → B[e] star with a luminosity greater than 104L_sun. A number of such objects exist in the → Magellanic Clouds, e.g. LMC R126, R66, SMC R4, and R50. A likely example in our Galaxy is MWC 300.
Fr.: cellule de supergranulation
One of a number of large convective cells (about 15,000-30,000 km in diameter) in the solar photosphere, distributed fairly uniformly over the solar disk, that last longer than a day.
Fr.: vapeur surchauffée
A vapor that has been heated above its boiling point temperature corresponding to the pressure.
The process in which a liquid is heated to a temperature higher than its boiling point, without boiling. Superheating is achieved by heating a homogeneous substance in a clean container, free of nucleation sites.
girande-ye abar-heterodini (#)
Fr.: récepteur superhétérodyne
A radio receiver which uses the → superheterodyne technique.
Fr.: technique superhétérodyne
The technique used in a radio receiver in which the frequency of an incoming signal is changed by adding it to a signal generated within the receiver to produce fluctuations or beats of a frequency equal to the difference between the two signals. See also → mixer.
An ion which is responsible for the existence of a strong → P Cygni profile observed in many early O stars. Since the → effective temperature of the star is too low to produce such an ion appreciably, the ion is termed a superion. For example, the ion O5+ which is at the origin of a strong O VI λλ1031, 1038 P Cygni profile observed in many O stars. Similarly, the lines due to N V λλ1238, 1242 belong to the superion category, while in later spectral types C IV λλ1548, 1552 also falls into this category. Initial modeling of the → ultraviolet line superions assumed the → stellar winds were smooth and homogeneous. However it is now generally accepted that the winds are (→ clumped wind), and this can have a profound influence on the formation of the superion profiles. We know that the strength of lines due to the superions is strongly influenced by the → interclump medium. Indeed, the interclump medium may be more important for producing the lines than are the clumps -- this is simply a consequence of the higher ionization in the interclump medium which occurs because of its lower density (see D. John Hillier, 2020, https://www.mdpi.com/2075-4434/8/3/60/htm, and references therein).
Upper or situated higher up in rank, degree, etc.
M.E., from O.Fr., from L. superiorem (nominative superior) "higher," comparative of superus "situated above, upper," from super "above, over," → super-.
Zabar, from Mid.Pers. azabar "above," related to abar (Mod.Pers. bar- "on, upon, up"); 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-, as above; O.H.G. ubir "over" + -in comparative suffix.
Fr.: conjonction supérieure
The conjunction of a planet with the Sun which occurs when the planet is beyond the Sun. → inferior conjunction.