  We consider a sonic analog of a black hole realized in the one-dimensional
flow of a Bose-Einstein condensate. Our theoretical analysis demonstrates that
one- and two-body momentum distributions accessible by present-day experimental
techniques provide clear direct evidence (i) of the occurrence of a sonic
horizon, (ii) of the associated acoustic Hawking radiation and (iii) of the
quantum nature of the Hawking process. The signature of the quantum behavior
persists even at temperatures larger than the chemical potential.
