GeminiFocus October 2017 - Page 16

Figure 2. 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. The inspiration for the research began sev- eral years ago, when Geballe used NIFS at Gemini North for an unrelated research program and serendipitously discovered a very faint and broad emission line due to hot helium gas near 1.7 microns in the in- frared spectrum of one of the Quintuplet stars. Prompted by this, he and his team ob- tained sensitive spectra of all five members of the Infrared Quintuplet, not only near 1.7 microns, but also down to wavelengths as short as 1.0 micron. The team’s spectra reveal the presence of emission lines from four of the five members of the Quintuplet, and have allowed the re- searchers to definitively identify the four as containing late-type, carbon-rich Wolf-Rayet stars, as was suspected based on the earlier imaging. These massive stars are only a few 14 GeminiFocus million years old, but have completely lost their outer hydrogen-rich layers and may be in the final stages of life before explod- ing violently as supernovae. The existence of this Infrared Quintuplet is yet another illustration of the effects of high densities of massive stars in some clusters and of the extreme conditions at the very heart of our Galaxy. Peter Michaud is the Public Information Out- reach Manager of Gemini Observatory. He can be reached at: [email protected] October 2017