Astrophysics (Index)About

Balmer jump

(Balmer discontinuity)
(abrupt change in stellar spectrum at end of Balmer series)

The Balmer jump (or Balmer discontinuity) is an abrupt change in the intensity of some stars' spectra for wavelengths shorter than the Balmer limit, the "infinity" end of the Balmer series spectral lines, i.e., 364.6 nm. It occurs when the star is sufficiently hot that hydrogen atoms with electrons at electron shell II are generally being ionized rather than moving to a higher level of atomic excitation. Photons of sufficient energy can be absorbed, lowering the continuum at the above-mentioned wavelength, and the sufficiently-hot star produces enough such photons to do this significantly. The shape of the jump is an indication of the star's density and temperature. The jump is strongest in early stars, e.g., A-type stars.


(stars,spectrum,Balmer series)
Further reading:
http://en.wikipedia.org/wiki/Balmer_jump
WaveLFreqPhoton
Energy
  
364.6nm822THz3.5eVBalmer jump

Referenced by pages:
Balmer-break galaxy (BBG)
blue horizontal branch (BHB)
spectral feature

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