  Many models of meta-stable supersymmetry (SUSY) breaking lead to a very light
scalar pseudo-Nambu Goldstone boson (PNGB), P, associated with spontaneous
breakdown of a baryon number like symmetry in the hidden sector. Current
particle physics data provide no useful constraints on the existence of P. For
example, the predicted decay rates for both K --> pi + P, b--> s + P and
Upsilon --> photon + P are many orders of magnitude below the present
experimental bounds. We also consider astrophysical implications of the PNGB
and find a significant constraint from its effect on the evolution of red
giants. This constraint either rules out models with a hidden sector gauge
group larger than SU(4), or requires a new intermediate scale, of order at most
10^{10} GeV, at which the hidden sector baryon number is explicitly broken.
