An Etymological Dictionary of Astronomy and Astrophysics
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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.

→ supergalactic; → plane.

A star with maximum intrinsic brightness and low density. The radius of a supergiant can be as large as 1000 times that of the Sun. See also → blue supergiant; → red supergiant; → yellow supergiant.

→ super-; → giant

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.

→ supergiant; → B[e] star.

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.

→ super-; → granulation; → cell.

A vapor that has been heated above its boiling point temperature corresponding to the pressure.

→ super-; → heat; → vapor.

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.

→ super-; → heating.

A radio receiver which uses the → superheterodyne technique.

→ super-; → heterodyne; → receiver.

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.

→ superheterodyne receiver; → technique.

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).

→ super-; → ion.

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.

The conjunction of a planet with the Sun which occurs when the planet is beyond the Sun. → inferior conjunction.

→ superior; → conjunction.

The meridian transit of a star between the celestial pole and the south point of the horizon. Same as → upper culmination. → inferior culmination.

→ superior; → culmination.

A planet whose orbit lies outside that of the Earth. The superior planets are Mars, Jupiter, Saturn, Uranus, and Neptune. → planet.

→ superior; → planet.

Apparent proper motion exceeding the velocity of light seen toward certain astronomical objects, such as the jets of radio galaxies and quasars. However, these jets are not actually moving at speeds in excess of the speed of light: the apparent superluminal motion is a projection effect caused by objects moving near the speed of light and at a small angle to the line of sight.

→ super-; luminal, from → lumen; → motion.

Jonbeš, → motion; abar→ super-; nur, → light.

The quality of an object whose luminosity exceeds a certain value.

→ super-; → luminous.

A → supernova with an → absolute magnitude of about -22 in optical. Examples of these newly discovered SNe include SN 2006gy, SN 2005ap, and SNe 2003ma. The nature of these objects is poorly known. Some of them are powered by the circumstellar interaction, or by the shock breakout from the dense circumstellar medium, as suggested by the presence of narrow emission lines in superluminous → Type II-N supernovae. It is also argued that superluminous SNe could be powered by a large amount of ⁵⁶Ni which is synthesized as a result of energetic → core-collapse supernovae. Other scenarios include the interaction between shells ejected by the pulsational → pair-instability. See, e.g. Tanaka et al. 2012, MNRAS 422, 2675, arXiv:1202.3610, and references therein.

→ superluminous; → supernova.

Having a mass highly exceeding a certain limit. → supermassive black hole, → supermassive neutron star, → supermassive star.

→ super-; → massive.

A → black hole of tremendous mass, equivalent to those of millions or even billions of stars, which is believed to exist and occupy the centers of many galaxies. The supermassive black hole residing in the center of our → Milky Way Galaxy is the object → Sgr A* with a mass of 4 x 10⁶→ solar masses within a radius of 100 → astronomical units.

→ supermassive; → black hole.

A → neutron star of mass above the typical value that is temporarily prevented from → collapseing into a → black hole because of its rapid → rotation.

→ supermassive; → neutron; → star.

A star with an initial mass over about 120 solar masses. The existence of such stars is the present Universe is not confirmed. Such stars were proposed as an explanation for very bright O type stars in the Large Magellanic Cloud, but these are now known to be clusters of ordinary O stars. → very massive star; → massive star.

→ supermassive; → star.