  We present the discovery of a plausible super-luminous supernova (SLSN),
found in the archival data of Sloan Digital Sky Survey (SDSS) Stripe 82, called
PSN 000123+000504. The supernova peaked at M_g<-21.3 mag in the second half of
September 2005, but was missed by the real-time supernova hunt. The observed
part of the light curve (17 epochs) showed that the rise to the maximum took
over 30 days, while the decline time lasted at least 70 days (observed frame),
closely resembling other SLSNe of SN2007bi type. Spectrum of the host galaxy
reveals a redshift of z=0.281 and the distance modulus of \mu=40.77 mag.
Combining this information with the SDSS photometry, we found the host galaxy
to be an LMC-like irregular dwarf galaxy with the absolute magnitude of
M_B=-18.2+/-0.2 mag and the oxygen abundance of 12+log[O/H]=8.3+/-0.2. Our SLSN
follows the relation for the most energetic/super-luminous SNe exploding in
low-metallicity environments, but we found no clear evidence for SLSNe to
explode in low-luminosity (dwarf) galaxies only. The available information on
the PSN 000123+000504 light curve suggests the magnetar-powered model as a
likely scenario of this event. This SLSN is a new addition to a quickly growing
family of super-luminous SNe.
