  Dense, small molecular cloud cores have been identified as the direct
progenitors of stars. One of the best studied examples is Barnard 68 which is
considered a prototype stable, spherical gas core, confined by a diffuse
high-pressure environment. Observations of its radial density structure however
indicate that Barnard 68 should be gravitationally unstable and collapsing
which appears to be inconsistent with its inferred long lifetime and stability.
We argue that Barnard 68 is currently experiencing a fatal collision with
another small core which will lead to gravitational collapse. Despite the fact
that this system is still in an early phase of interaction, our numerical
simulations imply that the future gravitational collapse is already detectable
in the outer surface density structure of the globule which mimicks the profile
of a gravitationally unstable Bonnor-Ebert sphere. Within the next 200,000
years Barnard 68 will condense into a low-mass solar-type star(s), formed in
isolation, and surrounded by diffuse, hot interstellar gas. As witnessed in
situ for Barnard 68, core mergers might in general play an important role in
triggering star formation and shaping the molecular core mass distribution and
by that also the stellar initial mass function.
