Ultrarelativistic heavy ion collisions produce a quark-gluon matter which lies in the future light cone originating from given points on the $t=z=0$ plane of the Minkowski spacetime manifold. We show that in a weak coupling regime the Minkowski vacuum of massless fields presents itself in the Little Bang region as a thermal state of low $p_{T}$ particles, in close analogy to the Unruh effect for uniformly accelerated observers which are causally restricted to a Rindler wedge. It can shed some light on the mechanisms of early time thermalization in ultrarelativistic heavy ion collisions.
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