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

Radiating light or other types of electromagnetic energy.

From L. luminosus "shining, full of light," from → lumen (gen. luminis) "light," related to lucere "to shine."

Tâbân "luminous," verbal adj. of tâbidan "to shine," variants tâftan "to shine," tafsidan "to become hot," related to tâb "heat, burning; heated iron; torment," âftâb "sunshine," tâbé "frying-pan," tab "fever;" dialect of Gaz tôu-, tôwâ "to shine;" Khotanese ttav- "to be hot;" Mid.Pers. tâftan "to heat, burn, shine;" taftan "to become hot;" Parthian tâb- "to shine;" Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "to heat, be/become hot; to spoil, injure, damage; to suffer," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "to be warm."

A high-luminosity variable star, which represents a transition phase in the life of a massive star when it evolves off the main sequence to become a supernova. Only about a dozen confirmed LBVs are presently known in our Galaxy. → Hubble-Sandage variable.

→ luminous; → blue; → variable.

A measure indicating the ability of a light source to emit visible light using a given amount of → power. It is a ratio of the visible energy emitted to the power that goes into the bulb from the electrical line.

→ luminous; → efficacy.

A measure of the rate of flow of luminous energy, evaluated according to its ability to produce a visual sensation. It is measured in lumens.

→ luminous; → flux.

A galaxy that emits most of its energy in the infrared and whose infrared luminosity (in the 8-1000 µm range) is more than 10¹¹ solar luminosities. → ultraluminous infrared galaxy.

→ luminous; → infrared; → galaxy.

A measure of the amount of light that a point source radiates in a given direction. It is expressed by the luminous flux per unit leaving the source in the direction per unit of solid angle.

→ luminous; → intensity.

Ordinary baryonic matter that can emit electromagnetic radiation, as opposed to → dark matter.

→ luminous; → matter.

A stellar explosion thought to be caused by the → merger of stars in a → binary system. They are characterized by a distinct red color, and a → light curve that lingers with resurgent brightness in the → infrared. The luminosity of the explosion is between that of a → supernova and a → nova.

→ luminous; → red; → nova

Not ordinary matter. Same as → dark matter.

→ non-; → luminous; → matter.

A star that is less luminous than a main-sequence star of the same spectral type.

→ sub-; → luminous; → star.

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.

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

→ ultra-; → luminous.

A galaxy that emits more than 90% of its energy in the infrared (8-1000 µm) and whose infrared luminosity exceeds 10¹² solar luminosities. → luminous infrared galaxy (LIRG). Quasars can also have such high or even higher bolometric luminosities. However LIRGs and ULIRGs emit the bulk of their energy in the infrared. Most of ULIRGs are found in merging and interacting galaxy systems. It is thought that their luminosity results from galactic collisions, which increase the rate of star formation.

→ ultraluminous; → infrared; → galaxy.

An X-ray source that is not in the nucleus of a galaxy, and is more luminous than 10³⁹ ergs s^-1, brighter than the → Eddington luminosity of a 10 → solar mass → black hole. In general, there is about one ULX per galaxy in galaxies which host ULXs. The Milky Way contains no such objects. ULXs are thought to be powered by → accretion onto a → compact object. Possible explanations include accretion onto → neutron stars with strong → magnetic fields, onto → stellar black holes (of up to 20 → solar masses) at or in excess of the classical Eddington limit, or onto → intermediate-mass black holes (10³-10⁵ solar masses). NGC 1313X-1, NGC 5408X-1, and NGC 6946X-1 are three ULXs with X-ray luminosities up to ~ 10⁴⁰ erg s^-1 (Ciro Pinto et al., 2016, Nature 533, N) 7601).

→ ultraluminous; → X-ray source.