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