Presenting the Baby Monster Original Research Article

We prove that Y433, is isomorphic to 2 × 2 · F2, where F2 is Fischer′s Baby Monster group. This answers the last open problem concerning the description of Y-groups. The result implies in particular that Y553 and Y555 are fabulous systems of generators for the Monster and Bimonster, respectively, in a sense introduced by J.Conway. We also give a new independent proof that Y555 is the Bimonster.