We present low resolution K band spectra taken at the Gemini 8 meter telescope of ( 90377 ) Sedna and ( 90482 ) Orcus ( provisional designations 2003 VB _ { 12 } and 2004 DW , respectively ) , currently the two minor planets with the greatest absolute magnitudes ( i.e .
the two most reflective minor planets ) .
We place crude limits on the surface composition of these two bodies using a Hapke model for a wide variety of assumed albedos .
The unusual minor planet ( 90377 ) Sedna was discovered on November 14 , 2003 UT at roughly 90 AU with 1.6 times the heliocentric distance and perihelion distance of any other bound minor planet .
It is the first solar system object discovered between the Kuiper Belt and the Oort Cloud , and may represent a transition population between the two .
The reflectance spectrum of ( 90377 ) Sedna appears largely featureless at the current signal-to-noise ratio , suggesting a surface likely to be highly processed by cosmic rays .
For large grain models ( 100 µm to 1 cm ) we find that ( 90377 ) Sedna must have less than 70 % surface fraction of water ice and less than 60 % surface fraction of methane ice to 3 \sigma confidence .
Minor planet ( 90482 ) Orcus shows strong water ice absorption corresponding to less than 50 % surface fraction for grain models 25 µm and larger .
Orcus can not have more than 30 % of its surface covered by large ( 100 mm to 1 cm ) methane grains to 3 \sigma confidence .