The matter beyond the ring: the recent evolution of SN 1987A observed by
  the Hubble Space Telescope
  The nearby SN 1987A offers a spatially resolved view of the evolution of a
young supernova remnant. Here we precent recent Hubble Space Telescope imaging
observations of SN 1987A, which we use to study the evolution of the ejecta,
the circumstellar equatorial ring (ER) and the increasing emission from
material outside the ER. We find that the inner ejecta have been brightening at
a gradually slower rate and that the western side has been brighter than the
eastern side since ~7000 days. This is expected given that the X-rays from the
ER are most likely powering the ejecta emission. At the same time the optical
emission from the ER continues to fade linearly with time. The ER is expanding
at 680\pm 50 km/s, which reflects the typical velocity of transmitted shocks in
the dense hotspots. A dozen spots and a rim of diffuse H-alpha emission have
appeared outside the ER since 9500 days. The new spots are more than an order
of magnitude fainter than the spots in the ER and also fade faster. We show
that the spots and diffuse emission outside the ER may be explained by fast
ejecta interacting with high-latitude material that extends from the ER toward
the outer rings. Further observations of this emission will make it possible to
determine the detailed geometry of the high-latitude material and provide
insight into the formation of the rings and the mass-loss history of the
progenitor.
