The dominating reionization source in the young universe has yet to be identified. Possible candidates include metal poor starburst dwarf galaxies of which the Blue Compact Galaxy Haro 11 may represent a local counterpart. Using the Far Ultraviolet Spectroscopic Explorer (FUSE) we obtained spectra of Haro 11 to search for leaking ionizing radiation. A weak signal shortwards of the Lyman break is identified as Lyman continuum (LyC) emission escaping from the ongoing starburst. From profile fitting to weak metal lines we derive column densities of the low ionization species. Adopting a metallicity typical of the H II regions of Haro 11, the corresponding H I column density is optically thick in the LyC. Therefore most of the LyC photons must escape through transparent holes in the interstellar medium. Using spectral evolutionary models we constrain the escape fraction of the produced LyC photons to between 4 and 10%, assuming a normal Salpeter IMF. We argue that in a hierarchical galaxy formation scenario, this allows for a substantial contribution to cosmic reionization by starburst dwarf galaxies at high redshifts.
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