  Most of the baryons from galaxies have been "missing" and several studies
have attempted to map the circumgalactic medium (CGM) of galaxies in their
quest. Recent studies with the Hubble Space Telescope have shown that many
galaxies contain a large reservoir of ionized gas with temperatures of about
10^5 K. Here we report on X-ray observations made with the Chandra X-ray
Observatory probing an even hotter phase of the CGM of our Milky Way at about
10^6 K. We show that this phase of the CGM is massive, extending over a large
region around the Milky Way, with a radius of over 100 kpc. The mass content of
this phase is over ten billion solar masses, many times more than that in
cooler gas phases and comparable to the total baryonic mass in the disk of the
Galaxy. The missing mass of the Galaxy appears to be in this warm-hot gas
phase.
