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

Same as → optical depth.

→ optical; → thickness.

The qualifier of a medium in which the → optical depth is large, significantly larger than 1.

→ optically; → thick.

A wind with the → sonic point located at large optical depth for continuum. In particular, → Wolf-Rayet star winds are → optically thick. However, the outer parts of W-R winds are → optically thin for continuum, and in those regions the matter flow is driven by the same mechanism as in the winds of OB stars.

→ optically; → thick; → wind.

Relatively great in extent from one surface to the opposite; deep or profound. &rarroptically thick

M.E. thikke, O.E. thicce "not thin, dense," from P.Gmc. *theku-, *thekwia- (cf. O.S. thikki, O.H.G. dicchi, Ger. dick), from PIE *tegu- "thick."

Setabr, from Mid.Pers. stabr "strong, big," stambag "pugnacious, opposing;" O.Pers. (mā) stabava [2sg.inj.] "to revolt;" Av. stabra- "strong, firm;" cf. Skt. stabh- "support," stambh- "to support, fix firmly," stabhnāti "supports;" Gk. astemphes "steadfast," stephein "to tie around, encircle," astemphes "firm, rigid;" Lith. stebas "staff, pillar," stembti "to oppose."

A disk component of a → spiral galaxy that lies above the → thin disk and mainly consists of stars. The thick disk of our → Galaxy makes up about 10-50% of the stellar mass of the → Milky Way and has a scale height of ~ 1,000-3,000 → light-years. Thick disk stars are, on average, moving faster in a vertical direction with respect to the → galactic plane than thin disk stars. In contrast to thin disk, the stars within the thick disk are almost all older than 10 billion years and typically have a smaller → metallicity than the average values for the thin disk stars. These facts suggest that the formation scenarios for the thin and thick disks were different. In particular, it is thought that the thick disk is much older than the thin disk.

→ thick; → disk;

A lens whose thickness is not small compared with its focal length. The thick lens may include several components, which may or may not be in contact. → thin lens.

→ thick; → lens.

The state or quality of being thick. → optical thickness.

M.E. thiknesse, O.E. thicnes, from → thick + -nes(s) suffix of action, quality or state, cf. M.Du. -nisse, O.H.G. -nissa, Ger. -nis, Goth. -inassus.

Setabrâ, from setabr→ thick + -â a suffix forming nouns from adjectives.