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

A uniqueness theorem involving the equations of state of stellar structure. → Vogt-Russell theorem.

Named after the German astronomer Heinrich Vogt (1890-1968) and the American astronomer Henry Norris Russell (1877-1957); → theorem.

A term inserted into a formula for the energy of a single electron in the outermost shell of an atom to take into account the failure of the inner electron shells to screen the nuclear charge completely.

→ rydberg; → correction.

A dwarf irregular galaxy, discovered in 1977, that is a member of the Local Group of galaxies. It has a diameter of 1,500 light-years and lies about 3.5 million light-years away. SagDIG contains as much as about 10⁸ solar masses of H I gas and is one of the most metal-poor galaxies. It should not be confused with the → Sagittarius Dwarf Elliptical Galaxy.

→ Sagittarius; → dwarf; → irregular; → galaxy.

A blue/violet light better seen at night on a pointed object, such as the mast of a ship or the wing of an airplane, during a → thunderstorm. The mast appears to be on fire but does not burn. It occurs when the ground below the storm is electrically charged, and there is high voltage in the air between the cloud and the ground. The high voltage causes the electrons and protons of the air molecules to be pulled away from each other, transforming the air into a glowing ionized gas. St. Elmo's fire is sometimes mistaken for → ball lightning. It was identified as an electrical phenomenon first by by Benjamin Franklin in 1749. Also called → corposant.

Saint Elmo the Italian rendering of St. Erasmus of Formiae (died 303) the patron saint of Mediterranean sailors; → fire.

Âtaš, → fire, sepant "saint, holy," → heiligenschein.

Same as → Nyquist-Shannon sampling theorem.

→ sampling; → theorem.

The maximum current that can be obtained in a specific circuit under specified conditions.

→ saturation; → current.

1) Occurring or distributed over widely spaced and irregular intervals in time or space.
2) The quality of a particle that has undergone → scattering.

Past participle of → scatter.

A → particle that causes → scattering of another particle through interaction with it.

→ scatter; → -er.

Same as the → Schmidt law.

Named after the American astrophysicists Maarten Schmidt (1929-), the pioneer of research in this field, and Robert C. Kennicutt, Jr. (1951-), who developed the study; → relation.

1) A large, usually flat surface onto which an image is projected for viewing.
2) The portion of a computer terminal or monitor upon which information is displayed.

M.E. screne; O.Fr. escren "a screen against heat," from M.Du. scherm "screen, cover," or Frank. *skrank "barrier;" cf. O.H.G. skirm, skerm "protection," scrank "barrier;" Ger. Schrank "cupboard."

Pardé, from Mid.Pers. pardag "curtain, veil, covering;" loaned in Armenian partak "veil," and Georgian p'ardag-i "curtain;" cognate with Gk. pelas, pella, L. pellis "skin;" O.E. filmen "thin skin;" PIE root *pel- "to cover."

A character used for on-screen → display. See also → printer font.

→ screen; → font.

The → Coulomb interaction reduced owing to the presence of other electrons. See → shielding effect.

→ screen; → coulomb; → interaction.

Same as → shielding effect.

→ screen; → effect.

A piece of metal, consisting of a threaded and usually tapered shank that has a slotted head by which it is turned into something in order to fasten things together.

M.E. scrwe, screw, from M.Fr. escroue "nut, cylindrical socket," of uncertain origin.

Pic "screw," present stem of picidan "to twist, entwine, coil."

The scientific attempt to detect → intelligent extraterrestrial → life by surveying the sky to find the existence of → transmissions, especially → radio waves or → light, from a → civilization on a distant → planet. The SETI Institute, that carries out the project, is a private non-profit center founded in 1984. There are many methods that SETI scientific teams use to search for extraterrestrial intelligence. Many of these search billions of radio frequencies that reach Earth from all over the → Universe, looking for an intelligent → radio signal. Other SETI teams search by looking for signals in pulses of light emanating from the stars.

→ search; → extraterrestrial; → intelligence.

A hydrostatic object predicted to result from the → second collapse of a → molecular cloud in an early stage of star formation.

→ second; → core.

A → dredge-up process that occurs after core helium burning, in which the convective envelope penetrates much more deeply, pushing hydrogen burning shell into close proximity with the helium burning shell (→ first dredge-up). This arrangement is unstable and leads to burning pulses. The reason is that the hydrogen shell burns out until there is enough helium for the helium combustion to occur and all the helium is rapidly burnt. Afterward the hydrogen shell again burns outward and the process repeats.

→ second; → dredge-up.

An atmosphere of a planet that forms after primordial gases had been lost or had failed to accumulate. A secondary atmosphere develops from internal volcanic outgassing, or by accumulation of material from comet impacts. It is characteristic of terrestrial planets, such as Earth, Mercury, Venus, and Mars. → primordial atmosphere.

→ secondary; → atmosphere.

1) Something that is or is kept secret, hidden, or concealed; a → mystery.
2) Done, made, or conducted without the knowledge of others (Dictionary.com).

From L. secretus "set apart, withdrawn; hidden, concealed," p.p. of secernere "to set apart, part, divide; exclude," from se- "without, apart," properly "on one's own" + cernere "to separate," → crisis.

Râz, from Mid.Pers. râz "secret, mystery;" cognate with Mod.Pers. rastan/rah- "to escape, be liberated;" O.Pers. (+*aua-) avarad- "to leave, abandon;" cf. Skt. rah- "to be lost, be lonely," rahas- "loneliness, privacy; a secret, mystery" (Cheung 2007).

The officials or office entrusted with administrative duties, maintaining records, and overseeing or performing secretarial duties, especially for an international organization (Dictionary.com).

From Fr. secrétariat, from M.L. secretariatus, from secretarius, → secretary.

Dabirxâné, literally "house of secretaries," from dabir, → secretary, + xâné, → house.