We introduce a new maximum likelihood method to model the density profile of Blue Horizontal Branch and Blue Straggler stars and apply it to the Sloan Digital Sky Survey Data Release 8 ( DR8 ) photometric catalogue .
There are a large number ( \sim 20,000 ) of these tracers available over an impressive 14 , 000 deg ^ { 2 } in both Northern and Southern Galactic hemispheres , and they provide a robust measurement of the shape of the Milky Way stellar halo .
After masking out stars in the vicinity of the Virgo Overdensity and the Sagittarius stream , the data are consistent with a smooth , oblate stellar halo with a density that follows a broken power-law .
The best fitting model has an inner slope \alpha _ { in } \sim 2.3 and an outer slope \alpha _ { out } \sim 4.6 , together with a break radius occurring at \sim 27 kpc and a constant halo flattening ( that is , ratio of minor axis to major axis ) of q \sim 0.6 .
Although a broken power-law describes the density fall-off most adequately , it is also well fit by an Einasto profile .
There is no strong evidence for variations in flattening with radius , or for triaxiality of the stellar halo .