We build a sample of distant ( D > 80 kpc ) stellar halo stars with measured radial velocities . Faint ( 20 < g < 22 ) candidate blue horizontal branch ( BHB ) stars were selected using the deep , but wide , multi-epoch Sloan Digital Sky Survey photometry . Follow-up spectroscopy for these A-type stars was performed using the VLT-FORS2 instrument . We classify stars according to their Balmer line profiles , and find 7 are bona fide BHB stars and 31 are blue stragglers ( BS ) . Owing to the magnitude range of our sample , even the intrinsically fainter BS stars can reach out to D \sim 90 kpc . We complement this sample of A-type stars with intrinsically brighter , intermediate-age , asymptotic giant branch stars . A set of 4 distant cool carbon stars is compiled from the literature and we perform spectroscopic follow-up on a further 4 N-type carbon stars using the WHT-ISIS instrument . Altogether , this provides us with the largest sample to date of individual star tracers out to r \sim 150 kpc . We find that the radial velocity dispersion of these tracers falls rapidly at large distances and is surprisingly cold ( \sigma _ { r } \approx 50 - 60 km s ^ { -1 } ) between 100-150 kpc . Relating the measured radial velocities to the mass of the Milky Way requires knowledge of the ( unknown ) tracer density profile and anisotropy at these distances . Nonetheless , by assuming the stellar halo stars between 50 - 150 kpc have a moderate density fall-off ( with power-law slope \alpha < 5 ) and are on radial orbits ( \sigma ^ { 2 } _ { t } / \sigma ^ { 2 } _ { r } < 1 ) , we infer that the mass within 150 kpc is less than 10 ^ { 12 } M _ { \odot } and suggest it probably lies in the range ( 5 - 10 ) \times 10 ^ { 11 } M _ { \odot } . We discuss the implications of such a low mass for the Milky Way .