The upper bound on the number of relativistic species present at nucleosynthesis has been used to constrain particles with electric charge $\epsilon e({10}^{-8\mathrm{}}<\epsilon <1)$. We correct the bound previously calculated for millicharged particles that interact with a shadow photon. We also discuss the additional constraints from the properties of red giants and of Supernova 1987A.

• Received 14 October 1993

DOI:https://doi.org/10.1103/PhysRevD.49.2114