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

Wide in extent from side to side.

M.E. bro(o)d, from O.E. brad; cf. O.N. breiðr, Du. breed, Ger. breit, Goth. brouþs.

Pahn "wide, broad," from Mid.Pers. pah(a)n; Av. paθana- "broad, wide, spacious;" PIE root *pete- "to spread;" cf. L. patere "to be open," Gk. petannynai "to spread out," petalon "a leaf."

Photometric measurements carried out through filters with a band-width (about one-tenth the central wavelength) in the range 30-100 nm. Typical examples are Johnson photometry, Krons-Cousins RI photometry, and the six-color system.

→ broad; → band; → photometry.

A radio galaxy that shows broad optical emission lines. → broad-line region.

→ broad; → line; → radio galaxy.

The inner region of a → quasar or an → active galactic nucleus exhibiting broad → spectral lines which indicate ionized matter moving with speeds in excess of 10,000 km sec^-1, probably due to the presence of an → accretion disk surrounding a → supermassive black hole. Also called Type I AGN. See also → obscuring torus.

→ broad; → line; → region.

To make or become broad or broader.

→ borad.

Pahnidan, from pahn, → broad, + -idan infinitive suffix.

The act of making something wider. → instrumental broadening; → line broadening.

Broadening, from → broad + → -ing noun froming suffix.

Pahneš, from pahn (→ broad, present tense stem of pahnidan "to broaden" + -idan infinitive suffix) + eš verbal-noun suffix.

In atomic physics, the broadening of an emission or absorption line due to the Doppler effect. Random motions of molecules or atoms of the gas that is emitting or absorbing the radiant energy shift the apparent wavelength of each emitter, and the cumulative effect of indivisual shifts is to broaden the line.

→ Doppler effect; → broadening.

The broadening of a point source caused by the response functions of the telescope and the instrument used.

→ instrumental; → broadening.

A widening of → spectral lines due to any of several factors, including the → Doppler broadening, → instrumental broadening, → microturbulence, → pressure broadening, → rotational broadening, the → Stark effect, and the → Zeeman effect.

→ line; → broadening.

The broadening of any spectral line due to the fact that excited levels have mean lives, which, by virtue of the uncertainty principle, implies a spread in the energy values.

→ natural; → line; → broadening.

A broadening of spectral lines caused mainly by the stellar atmospheric density and the surface gravity of the star. The line strength of a spectral line depends on the number of atoms in the star's atmosphere capable of absorbing the wavelength in question. For a given temperature, the more atoms there are, the stronger and broader the spectral line appears. Denser stars with higher surface gravity will exhibit greater pressure broadening of spectral lines.

→ pressure; → broadening.

The spectral line broadening caused by stellar rotation. Light from two rims of the star will be Doppler shifted in opposite directions, resulting in a line broadening effect. The line broadening depends on the inclination of the star's pole to the line of sight. The derived value is a function of v_e. sini, where v_e is the rotational velocity at the equator and i is the inclination, which is not always known. The fractional width (Δλ/λ) is of the order of 10^-3 for B stars.

→ rotational; → broadening.