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

Same as → Little Dipper.

→ small; → Little Dipper.

The interval after which the heliacal rising of the star Sirius occurs at the same time of the year. It is a period of 1,460 Sothic years.

From Fr. sothique, from Gk. Sothis, an Egyptian name of Sirius; → period.

Tištari, of or pertaining to Tištar→ serius; dowré, → period.

→ dispersion.

→ spectral; → dispersion.

The → excitation temperature of the → hyperfine structure levels of the → neutral hydrogen→ 21-centimeter line.

→ spin; → temperature.

1) The most commonly used definition is temperature of 273.15 K (0 °C) and pressure of 1 → atmosphere.
2) Chemistry: Temperature of 273.15 K (0 °C) and pressure of 10⁵  → pascal (Pa)s (1 → bar). International Union of Pure and Applied Chemistry (IUPAC) recommends that the former use of the pressure of 1 atm as standard pressure (equivalent to 1.01325 × 10⁵ Pa) should be discontinued.

→ standard; → temperature; → pressure.

An experiment devised for measuring the → magnetic moment of → silver atoms. A → beam of silver atoms is directed between the → poles of a non-homogeneous → magnetic field. Contrarily to the prediction of the classical theory, the atoms divide into two distinct parts. One half of atoms are deflected up, the other half deflected down. The amount of deflection up or down is exactly of the same magnitude. Whether an individual atom is deflected up or down appears to be random. From a measurement of the → deflection, one can find the strength of the magnetic moment. This experience provides proof that there exist only two permitted orientations, called the → quantization of → spin.

In honor of Otto Stern (1888-1969), German physicist, Nobel laureate in Physics 1943, and Walter Gerlach (1889-1979), German physicist, who carried out the experiment in 1922. They used a beam of silver atoms from a hot oven because they could be readily detected on a photograph emulsion. Moreover, the silver atoms allowed studying the magnetic properties of a single electron because the atoms have a single outer electron; → experiment.

Same as → perigee full Moon.

→ super-; → Moon.

A group of hundreds to thousands of very young stars packed into an unbelievably small volume of a few parsecs in size. These objects represent the youngest stage of → massive star cluster evolution yet observed. The most massive and dense SSCs, with ages less than 10⁶ years, may be proto globular clusters. SSCs are thought to dissolve within 10 million years and merge into the field star population.

→ super; → star; → cluster.

A prefix occurring originally in loanwords from Latin, with the basic meaning "above, beyond."

L. adverb and preposition super "above, over, on the top (of), beyond, besides, in addition to," from PIE base *uper "over," cognate with Pers. abar-, as below.

Mid.Pers. 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."

A star whose mass exceeds the → canonical upper limit of the stellar → initial mass function (Kroupa et al. 2012, arXiv:1112.3340).

→ super-; → canonical; → star.

A superluminous → Type Ia supernova which is characterized by a bright → light curve peak, a slow light curve evolution during the photospheric phase, and moderately low ejecta velocities. Modeling suggests ejecta masses far in excess of the → Chandrasekhar limit of mass for non-rotating → white dwarfs and the production of about 1.5 Msun of ⁵⁶Ni. This precludes the interpretation of these events as thermonuclear explosions of Chandrasekhar-mass white dwarfs.

→ super-; → Chandrasekhar limit.

An → extrasolar planet more massive than the Earth but less massive than 10 → Earth masses. The first discovered super-Earth orbits an M4 V star named GJ 876. Its estimated mass is 7.5±0.7 Earth masses and it has an orbital period of 1.94 days. It is close to the host star, and the surface temperature is calculated to lie between 430 and 650 K (Rivera et al. 2005, ApJ 634, 625).

→ super-; → Earth.

A → stellar wind accelerated by radiation pressure in the continuum from a star with a luminosity above the → Eddington limit.

→ super-; → Eddington limit; → wind.

A very → metal-rich star whose iron → metallicity, [Fe/H], exceeds 0.20 → dex. Examples include HD 32147, HD 121370, and HD 145675 (Feltzing & Gonzalez, 2001, A&A 367, 253).

→ super-; → metal; → rich; → star.

A condition in which there is an excess of the actual temperature gradient over the → adiabatic temperature gradient corresponding to the same pressure gradient. A region with superadiabatic temperature gradient is convectively unstable. → Hayashi forbidden zone.

→ super-; → adiabatic; → temperature; → gradient.

A cavity hundreds of light-years across filled with a hot gas blown into the interstellar medium by multiple supernovae and stellar winds. Examples are the Local Bubble in the Orion Arm of the Milky Way and the N44 Superbubble in the Large Magellanic Cloud.

→ super-; → bubble

1) An aggregation of clusters of galaxies (→ galaxy cluster). Superclusters are typically about one hundred million (10⁸) → light-years in diameter and contain tens of thousands of galaxies. Some examples are the → Local Supercluster, → Centaurus supercluster, → Laniakea supercluster, → Perseus-Pisces supercluster→ Shapley supercluster→ Virgo supercluster.
2) For stellar aggregations, → dynamical stream.

→ super-; → cluster

Grouping of galaxies in supercluster structure.

→ super-; → clustering

The phenomenon in which certain materials, when cooled to a sufficiently low temperature, lose all resistance to the flow of electricity.

→ super-; → conductivity

A material which shows almost perfect conductivity at temperatures approaching absolute zero.

→ super-; → conductor.