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Balmer series Reference Libraries

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H II Region
2004-10-19 04:45:41

H II Region -- An H II region is an emission nebula associated with hot, young, blue stars, and star forming regions. H II, or singly-ionized hydrogen, is nebular gas ionized by ultraviolet light emitted by these hot, young stars of spectral type O and B. The sizes of H II regions are determined both by the amount of gas present, and by the luminosity of the O and B stars -- the more...

Word of the Day
sudarium
  • A handkerchief.
  • Specifically— The legendary sweat-cloth; the handkerchief of St. Veronica, according to tradition miraculously impressed with the mask of Christ; also, the napkin about Christ's head (Johu xx. 7).
  • In general, any miraculous portrait of Christ.
The word 'sudarium' comes from a Latin word meaning 'a handkerchief'.