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

A conspicuous band of molecular → CH (methylidine) at 4300 Å, which is present in the spectra of late-type G-K stars.

G refers to → G type stars in the spectra of which this feature is strong. → band.

A band in the → absorption spectrum of → ozone (O₃) extending in the → ultraviolet from 200 nm to 300 nm. It is stronger than the → Huggins band. See also: → Hartley band.

W. N. Hartley, J. Chem. Soc. 39, 111 (1881).

A band in the → absorption spectrum of → ozone (O₃) extending in the → ultraviolet from 310 nm to 370 nm. It is located at the red end of the strong → Hartley band.

W. Huggins and M. Huggins, Proc. R. Soc. London 48, 216 (1890).

A sequence of → permitted transitions in the → ultraviolet from an → excited state (B) of the → molecular hydrogen (H₂) to the electronic → ground state, with ΔE > 11.2 eV, λ < 1108Å (first → band head). When a hydrogen molecule absorbs such a photon, it undergoes a transition from the ground electronic state to the excited state (B). The following rapid → decay creates an → absorption band in that wavelength range. See also → Werner band. → Lyman-Werner photon.

→ Lyman (Th. Lyman, 1906, Astrophys. J. 23, 181); → band.

A surface with only one side, made by putting a simple twist in a long, rectangular strip of paper, then pasting the ends together.

After the German astronomer and geometer August Ferdinand Möbius (1790-1868); → band.

A band of molecular origin present in a spectrum. See for example → cyanogen band, → S star.

→ molecular; → band.

Optics: Of a filter, same as → interference filter.
Radio.: Encompassing a small frequency range, typically less than 300 Hz.

→ narrow; → band.

Photometry using narrow-band filters to isolate a particular spectroscopic line or molecular band.

→ narrow band; → photometry.

The range of wavelengths that are transmitted by a filter. Same as → band-pass.

Pass from O.Fr. passer, from V.L. *passare "to step, walk, pass," from L. passus "step, pace;" cf. Pers. pâ "foot," pey "step;" → band.

Gozar "passage, transit, passing," from gozaštan "to pass, cross, transit," variant gozâštan "to put, to place, let, allow;" Mid.Pers. widardan, widâštan "to pass, to let pass (by);" O.Pers. vitar- "to pass across," viyatarayam "I put across;" Av. vi-tar- "to pass across," from vi- "apart, away from" ( O.Pers. viy- "apart, away;" Av. vi- "apart, away;" cf. Skt. vi- "apart, asunder, away, out;" L. vitare "to avoid, turn aside") + O.Pers./Av. tar- "to cross over"); bând, → band.

The range of → wavelengths allowed by a → filter used in a → photometric system.

→ photometric + → band.

Certain frequencies, not used for civil or military purposes (radio, television, communication channels, etc.), which are protected for research in radioastronomy, one such being 21 cm.

Protected p.p. of protect, from L. protectus, p.p. of protegere "protect, cover in front," from → pro- "in front" + tegere "to cover;" → band.

Bând, → band; negahdâridé p.p. of negahdâridan, variant of negahdâštan "to keep, behold, preserve, take care of," from negah, negâh "watch, care, custody, look" + (Mid.Pers. nikâh "look, glance, observation;" Proto-Iranian *ni-kas- "to look down," from ni- "down" (cf. O.Pers. ni preposition and verbal prefix "down;" Av. nī "down, in ,into;" Skt. ni "down," nitaram "downward;" Gk. neiothen "from below;" E. nether; O.E. niþera, neoþera "down, downward, below, beneath," from P.Gmc. *nitheraz (O.S. nithar, O.N. niðr, O.Fris. nither, Du. neder, Ger. nieder); PIE *ni- "down, below") + *kas- "to look, appear;" cf. Av. nikā-, nikāta- (in the name of the 15-th nask) "that which is observed," ākas- "to look;" Mid.Pers. âkâh, Mod.Pers. âgâh "aware, knowing;" Skt. kāś- "to become visible, appear;" Ossetic kast/kaesyn "to look") + dâridan, dâštan "to have, hold, maintain, possess" (Mid.Pers. dâštan; O.Pers./Av. root dar- "to hold, keep back, maintain, keep in mind;" cf. Skt. dhr- "to to hold, keep, preserve," dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE *dher- "to hold, support").

Faint wavy lines of alternating light and dark that sometimes can be seen on flat, light-colored surfaces just before and just after a total solar eclipse. The phenomenon results from sunlight distortion by irregularities in the Earth's atmosphere.

→ shadow; → band.

Either of the two bands of frequencies, one just above (upper side) and one just below (lower side) a carrier frequency, that result from modulation of a carrier wave.

→ side; → band.

Bând, → band; kenâr "side," variant karân "edge, limit;" Mid.Pers. karân, karânak, kenâr "edge, limit, boundary;" Av. karana- "side, boundary, end."

One of the three prominent bands in the spectra of comets and carbon stars caused by diatomic carbon (C₂).

Named after the Scottish physicist William Swan (1818-1894) who first studied the spectral analysis of radical carbon C₂ in 1856; → band.

A band seen in the spectra of celestial objects, which is due to absorption by gases such as oxygen, water vapor, and carbon dioxide in the Earth's atmosphere

→ telluric; → band.

Any of the several → absorption bands due to the molecule → titanium oxide that are prominent in the spectra of cool → K and → M stars.

→ titanium oxide; → band.

The frequency range above the cutoff frequency in a waveguide or transmission line.

→ transmission; → band.

A no longer in general use name for → Aromatic Infrared Band.

→ unidentified; → infrared; → band.

The range of energy states in the spectrum of a solid crystal which includes the energies of all the electrons binding the crystal together.

→ valence; → band.

A portion of the electromagnetic spectrum which is defined because of its characteristics or for its use.

→ wave; → band.