  We report the discovery of large scale diffuse non-thermal radio emission in
PLCK G287.0+32.9, an exceptionally hot (T ~ 13 keV), massive and luminous
galaxy cluster, strongly detected by the PLANCK satellite in a recent, all-sky
blind search for new clusters through Sunyaev-Zel'dovich effect. Giant
Metrewave Radio telescope 150 MHz and Very Large Array 1.4 GHz radio data
reveal a pair of giant (>1 Mpc) "arc" shaped peripheral radio-relics
(signatures of shock waves) of unprecedented scale (linear separation ~4.4 Mpc
at redshift 0.39), located at distances from the cluster center which are about
0.7 and 1.3 of the cluster's virial radius. Another possible giant relic and a
radio-halo is detected closer to the cluster center. These relic sources are
unique "signposts" of extremely energetic mergers and shocks (both ongoing and
past), that are assembling and heating up this very massive galaxy cluster.
They are also a probe of the filamentary cosmic-web structure beyond the
cluster virial radius. Optical imaging with the IUCAA 2 meter telescope and
XMM-Newton X-ray data confirm a very rich galaxy cluster with a morphologically
disturbed core region, suggesting a dynamically perturbed merging system.
