  We have undertaken deep, high-resolution observations of SN 1987A at ~20
years after its explosion with the Chandra HETG and LETG spectrometers. Here we
present the HETG X-ray spectra of SN 1987A having unprecedented spectral
resolution and signal-to-noise in the 6 A to 20 A bandpass, which includes the
H-like and He-like lines of Si, Mg, Ne, as well as O VIII lines and bright Fe
XVII lines. In joint analysis with LETG data, we find that there has been a
significant decrease from 2004 to 2007 in the average temperature of the
highest temperature component of the shocked-plasma emission. Model fitting of
the profiles of individual HETG lines yields bulk kinematic velocities of the
higher-Z ions, Mg and Si, that are significantly lower than those inferred from
the LETG 2004 observations.

Astrophysics