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

The → line wing with wavelengths shorter than that of the emission or absorption peak.

→ blue; → wing.

A → line broadening phenomenon involving the scattering effect of → free electrons on the → radiation transfer in → stellar atmospheres. The scattering of radiation by free electrons plays an important role in the atmospheres of → hot stars, such as → O-types, early → B-types, and → Wolf-Rayet stars. The first detailed study of electron scattering in Wolf-Rayet stars was by Castor et al. (1970), who used electron scattering to explain the broad emission wings of N IV λ3483 in HD 192163. In → P Cygni stars the explanation of the very extended (almost symmetric) wings on the → Balmer lines as caused by electron scattering was first made by Bernat & Lambert (1978). Hillier (1991) showed that significant reduction in the strength of an electron-scattering wing can be achieved in a model of → clumped wind for a lower mean → mass loss rate. This resulted in a better agreement between observations and theoretical predictions. Electron-scattering wings provide diagnostics regarding the presence of density inhomogeneities in → stellar winds (Münch, 1948, ApJ 108, 116; Hillier, 1991, A&A 247, 455).

→ electron; → scattering; → wing.

Part of the line profile between the continuum level and the half value of the emission or absorption peak. The wings are due to matter traveling at much greater speeds than that providing the main peak. → red wing; → blue wing.

→ line; → wing.

Of a spectral line profile, the → line wing with wavelengths longer than that of the emission or absorption peak.

→ red; → wing.

A large cloud of faint stars extending eastward from the → Small Magellanic Cloud to the → Large Magellanic Cloud. The wing is in fact the tail of a much larger → neutral hydrogen structure linking the SMC to the LMC. Models and observations suggest that the structure known as the → Magellanic Stream results from the Clouds' interaction with each other and the Milky Way. Several works support the finding that the SMC wing is pointing toward the LMC, and is therefore closer to us than the SMC bar.

Named after the American astronomer Harlow Shapley (1885-1972), who discovered this structure (1940, Harvard Bull., 914, 8); → wing.

The action of rapidly moving a telescope in the alpha or delta direction under computer control as it moves to point at a new position in the sky.

Slew "to turn, swing, twist," earlier slue a nautical word, of unknown origin.

Tondrâneš, literally "driving fast," from tond "swift, rapid, brisk; fierce, severe" (Mid.Pers. tund "sharp, violent;" Sogdian tund "violent;" cf. Skt. tod- "to thrust, give a push," tudáti "he thrusts;" L. tundere "to thrust, to hit" (Fr. percer, E. pierce, ultimately from L. pertusus, from p.p. of pertundere "to thrust or bore through," from per- + tundere, as explained); PIE base *(s)teud- "to thrust, to beat") + râneš, verbal noun of rândan "to push, drive, cause to go," causative of raftan "to go, walk, proceed" (present tense stem row-, Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack").

A motor designed to drive a high-speed radar antenna for slewing to monitor a target.

→ slewing; → drive

The maximum angle at which a display, such as a TV screen, can be viewed with acceptable visual performance.

Viewing, from view, M.E. v(i)ewe (n.); M.Fr. veue "sight," feminine p.p. of veoir "to see," from L. videre "to see," → vision; → angle.

Zâviyé, → angle; did→ vision.

1) Either of the two limbs of a bird allowing her to fly. → Pegasus.
2) Either of the large flat structures in an aircraft's body that provide the main source of lift.
3) In spectroscopy, same as → line wing.

M.E. wenge from O.N. vængr "wing of a bird, aisle, etc." (cf. Dan., Swed. vinge "wing").

Bâl "wing," Mid.Pers. bâl, variant of par / parr "feather, " with the conversion of p to b and r to l; Av. parəna- "feather;" cf. Skt. parnam; O.H.G. farn "fern;" PIE pornom "feather."

A spectral feature at 9850-10200 Å appearing in the spectrum of some late-type → M dwarfs. It is attributed to iron hybrid (FeH), a typical signature of the atmospheres of the coolest stars.

First detected by R. F. Wing and W. K. Ford (1969, PASP 81, 527); → band.