Complex sentence: Because the 56 Co in SN1987A has now completely decayed, the luminosity of the SN 1987A ejecta is currently powered by the radioactive decay of 44 Ti with a half life of about 60 years.
Split into simpler sentences: Because the 56 Co in SN1987A has today completely decayed, it no longer supports the luminosity of the SN 1987A ejecta. That is currently powered by the radioactive decay of 44 Ti with a half life of about 60 years.