  Stars in the mass range 8 Msun<M<30 Msun are thought to end their lives as
luminous supernovae that leave behind a neutron star. However, if a substantial
fraction of these stars instead ended as black-hole remnants, without producing
a supernova (a `failed' supernova), how would one know? We show that, under
plausible assumptions, the Hipparcos catalog should contain about 30 f_{fail}
astrometric binaries with black-hole companions, where f_{fail} is the fraction
of supernovae that fail. Since no black-hole astrometric binaries are found in
Hipparcos, one might like to conclude that such failed supernovae are very
rare. However, the most important assumption required for this argument, the
initial companion mass function (ICMF) of G stars (the majority of Hipparcos
stars) in the high-mass companion regime, is without any observational basis.
We show how the ICMF of G stars can be measured using the Full-Sky Astrometric
Explorer (FAME), thereby permitting an accurate measurement of the rate of
supernovae that fail.
