nebular lines

nebular lines

[′neb·yə·lər ′līnz]
(astrophysics)
The spectral lines formed in the glow of bright nebulae; they arise from forbidden atomic transition which can take place because of the very low pressure in the nebula itself.
References in periodicals archive ?
There were "encouraging results or (I should say) indications," Slipher reported to Lowell, "as there appears to be an appreciable displacement of the nebular lines toward the violet.