  We present a multi-wavelength study of a newly discovered compact group (CG),
SDSS J0959+1259, based data from XMM-Newton, SDSS and the Calar Alto optical
imager BUSCA. With a maximum velocity offset of 500 km s$^{-1}$, a mean
redshift of 0.035, and a mean spatial extension of 480 kpc, this CG is
exceptional in having the highest concentration of nuclear activity in the
local Universe, established with a sensitivity limit L$_{X}>4\times $10$^{40}$
erg s$^{-1}$ in 2--10 keV band and R-band magnitude $M_R < -19$. The group is
composed of two type-2 Seyferts, one type-1 Seyfert, two LINERs and three star
forming galaxies. Given the high X-ray luminosity of LINERs which reaches $\sim
10^{41}$ erg s$^{-1}$, it is likely that they are also accretion driven,
bringing the number of active nuclei in this group to to 5 out of 8 (AGN
fraction of 60\%). The distorted shape of one member of the CG suggests that
strong interactions are taking place among its galaxies through tidal forces.
Therefore, this system represents a case study for physical mechanisms that
trigger nuclear activity and star formation in CGs.
