  The possible existence of compact stars made of absolutely stable strange
quark matter--referred to as strange stars--was pointed out by E. Witten almost
a quarter of a century ago. One of the most amazing features of such objects
concerns the possible existence of ultra-strong electric fields on their
surfaces, which, for ordinary strange matter, is around $10^{18}$ V/cm. If
strange matter forms a color superconductor, as expected for such matter, the
strength of the electric field may increase to values that exceed $10^{19}$
V/cm. The energy density associated with such huge electric fields is on the
same order of magnitude as the energy density of strange matter itself, which,
as shown in this paper, alters the masses and radii of strange quark stars at
the 15% and 5% level, respectively. Such mass increases facilitate the
interpretation of massive compact stars, with masses of around $2 M_\odot$, as
strange quark stars.
