2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/199716We present a possible explanation of the recently observed 511 keV $γ$-ray anomaly with a new ``millicharged'' fermion. The new fermion is light (${\cal O}({\rm MeV})$) but has never been observed by any collider experiments mainly because of its tiny electromagnetic charge $εe$. We show that constraints from its relic density in the Universe and collider experiments allow a parameter range such that the 511 keV cosmic $γ$-ray emission from the galactic bulge may be due to positron production from this millicharged fermion.14 pages, 3 figures; To appear in Phys. Rev. DAstrophysicsHigh Energy Physics - Phenomenologytext