Recombination Lines

  • Thomas L. Wilson
  • Susanne Hüttemeister
Part of the Astronomy and Astrophysics Library book series (AAL)


A spherically symmetric, uniform HII region is ionized by an O7 star (mass about 50 M), with an excitation parameter, which is defined as \(\mathrm {U} = \mathrm {N}_{\mathrm {e}}^{2/3} \, \mathrm {L(pc)} \) U = 68 pc cm2∕3. Background information needed: The excitation parameter U is used in the following problem. U is the radius of the HII region (in pc), multiplied by the 2∕3 power of the electron density.

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Thomas L. Wilson
    • 1
  • Susanne Hüttemeister
    • 2
  1. 1.Max-Planck-Institut für RadioastronomieBonnGermany
  2. 2.Zeiss-Planetarium BochumBochumGermany

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