Phosphine has long been held as evidence of
turbulent mixing in Jupiter’s atmosphere. In
chemical equilibrium, phosphine is converted to phosphorus trioxide at temperatures
less than ~1,000 K. In Jupiter, hot phosphinerich gas from the interior is mixed into the
photosphere at a faster rate than the phosphine is destroyed. WISE 0855 does not show
the same mixing behavior, despite the fact
that it is warmer than Jupiter and should not
have to mix phosphine as far. This result will
be studied in more detail in a future paper.
Future Explorations
WISE 0855 will be an early target of the
James Webb Space Telescope (JWST). But
surprises in its spectrum suggest that we
need to continue iterating our theoretical
understanding of cold brown dwarfs and
exoplanets before JWST launches. Is Gemini
done with WISE 0855? Hopefully not; having
solved many of the technical problems that
make faint thermal-infrared spectroscopy
so difficult, we have been allocated time to
pursue its 3.8-4.1 micron spectrum. At these
wavelengths, we expect to see the influence of methane chemistry instead of water
chemistry, and we will refine estimates of
WISE 0855’s luminosity, which directly impacts its temperature and mass.
6
GeminiFocus
We also are continuing to study the coldest
brown dwarfs at M-band. Previous observations only went down to 700 K. There’s a big
jump from 700 K to 250 K, which we expect
contains the formation of water clouds. With
five more brown dwarfs spanning the 250700 K gap, we hope to study the depths of
water absorption lines, which models predict will increase with decreasing temperature until water clouds start to mute them,
and/or remove a significant fraction of the
available water vapor.
Gemini was designed to do thermal infrared spectroscopy, and Maunakea is the best
site on Earth to do it. From the telescope, to
the weather, to the instrument and observers, a lot had to work right to complete this
observation. It’s a testament to Gemini that
when WISE 0855 was discovered, GNIRS was
ready and able to obtain a spectrum for our
team’s work.
Andy Skemer is an Assistant Professor at the University of California Santa Cruz. He can be contacted at: [email protected]
October 2016