J-band spectra of three of the five members of the Infrared Quintuplet showing emission lines of neutral helium and ionized carbon

J-band spectra of three of the five members of the Infrared Quintuplet showing emission lines of neutral helium and ionized carbon. The continuum radiation from the stars and their dust shells actually decrease rapidly from longer to shorter wavelengths and is barely detectable at the short wavelength edge of these spectra. In the figure the spectra have been “flattened” to more easily reveal the line emission. The increasing “noisiness” of the spectra toward their short wavelength edges demonstrates the increasing difficulty of detecting any light at all from these objects at those wavelengths.