5.2.1 The companion of SBS0335-052
Like IZw18, SBS0335-052 also has a physical companion, SBS 0335-052W at a projected distance of 22 kpc (Pustilnik et al. 1999). Lipovetsky et al. (1999) found an oxygen abundance of 12 + log(O/H) = 7.2, even lower than that of SBS0335-052, and fully comparable to IZw18. This companion, though blue is not very compact and it has evidently avoided inclusion in any BCG catalogue. Its central R surface brightness and SFR is rather low, comparable to a ``normal'' dI. The fact that both SBS0335-052 and its companion resides in the same H I cloud but at least 22 kpc apart, poses a problem for the youth hypothesis since it would require a coordinated ignition of star formation in the two clouds.