  We report on the X-ray emission from the shell-like, non-thermal radio source
Sgr A East located in the inner few parsecs of the Galaxy based on observations
made with the ACIS detector on board Chandra. This is the first time Sgr A East
has been clearly resolved from other complex structures in the region. The
X-ray emitting region is concentrated within the central $\simeq 2$ pc of the
larger radio shell. The spectrum shows strong K$\alpha$ lines from highly
ionized ions of S, Ar, Ca, and Fe. A simple isothermal plasma model gives
electron temperature $\sim 2$ keV, absorption column $\sim 1 \times 10^{23}$
H/cm^2, luminosity $\sim 8 \times 10^{34}$ ergs/s in the 2--10 keV band, and
gas mass $\sim 2\eta^{1/2}$ M$_{\odot}$ with a filling factor $\eta$. The
plasma appears to be rich in heavy elements, over-abundant by roughly a factor
of four with respect to solar abundances, and shows a spatial gradient of
elemental abundance: the spatial distribution of iron is more compact than that
of the lighter elements. The gas mass and elemental abundance of the X-ray
emission support the long-standing hypothesis that Sgr A East is a supernova
remnant (SNR), maybe produced by the Type II supernova explosion of a massive
star with a main-sequence mass of 13--20 M$_\odot$. The combination of the
radio and X-ray morphologies classifies Sgr A East as a new metal-rich ``mixed
morphology'' (MM) SNR. The size of the Sgr A East radio shell is the smallest
of the known MM SNRs, which strongly suggests that the ejecta have expanded
into a very dense interstellar medium. The ejecta-dominated chemical
compositions of the plasma indicate that the ambient materials should be highly
homogeneous. The relation between Sgr A East and the massive blackhole Sgr A*
is discussed.
