A few supernovae, such as SN 1987K and SN 1993J, appear to change types: they show lines of hydrogen at early times, but, over a period of weeks to months, become dominated by lines of helium.
少數的超新星，像是SN 1987K和SN 1993J，顯示出類型的改變：初期，它們顯示出氫的譜線，但是經過幾週或幾個月的衰減期之後，光譜中主要是氦的譜線。