Two new young galactic supernova remnants

Substantial reductions^1-3 in the distances inferred for the remnants of several `historical' supernovae, coupled with a galactic supernova rate of 1 every 25 yrs or so⁴, have raised the possibility⁵ that many young but distant galactic supernova remnants may be missing from present catalogues. We have now used the Very Large Array (VLA) and the Cambridge 5-km telescope to observe 32 small-diameter objects selected from galactic plane radio surveys. These observations reveal both a new young shell remnant (which, at only ~1 arc min in extent, is the smallest angular size galactic remnant yet discovered), and a very peculiar radio source, probably a supernova remnant only a few hundred years old, which is still in the free expansion phase.