Statistics for a sample of 178 supernovae in external galaxies are presented which show convincingly that at least most Type I supernovae (SN I), viz., those in spiral and irregular galaxies, are associated with a young stellar population. Relative SN rates in galaxies of different types are discussed which establish an association between SN I and newly formed stars, at least in spirals and irregulars, and SN rates in spirals are derived as a function of color, confirming this association. Problems of associating SN I in elliptical galaxies with ongoing star formation are also considered. It is concluded that SN I have fairly short-lived precursors, with lifetimes between a few tens of millions of years and a few hundred million years.
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A. et al. (1979) studied this question.