Original sentence: Gamma rays from the decay of titanium-44 (half-life 90 years) were independently discovered coming from it, showing that it must have exploded fairly recently (perhaps around 1200 AD), but there is no historical record of it.In 1998 a supernova remnant, RX J0852.0-4622, was found in front (apparently) of the larger Vela Supernova Remnant
Edited sentence: In the late 1990's it was proposed that recent supernova remnants could be found by looking for gamma rays from the decay of titanium-44.The gamma rays from the decay of titanium-44 showed that it must have exploded fairly recently (perhaps around 1200 AD), but there is no historical record of it.This has a half-life of 90 years and the gamma rays can traverse the galaxy easily, so it permits us to see any remnants from the last millennium or so.This remnant (RX J0852.0-4622) had been found in front (apparently) of the larger Vela Supernova Remnant.Two sources were found, the previously discovered Cassiopeia A remnant, and the RX J0852.0-4622 remnant, which had just been discovered overlapping the Vela Supernova Remnant