▁are ▁indic ations ▁that ▁they ▁origin ate ▁as ▁stars ▁similar ▁to ▁L umin ous ▁blue ▁variables ▁with ▁large ▁mass ▁losses ▁before ▁expl oding . ▁ ▁SN   1 9 9 8 S ▁and ▁SN   2 0 0 5 gl ▁are ▁examples ▁of ▁Type   I In ▁super nov ae ; ▁ ▁SN   2 0 0 6 gy , ▁an ▁extremely ▁ener get ic ▁super n ova , ▁may ▁be ▁another ▁example . ▁ ▁Type   II b ▁super nov ae ▁A ▁Type   II b ▁super n ova ▁has ▁a ▁weak ▁hydro gen ▁line ▁in ▁its ▁initial ▁spectrum , ▁which ▁is ▁why ▁it ▁is ▁class ified ▁as ▁a ▁Type   II . ▁However , ▁later ▁on ▁the ▁H ▁emission ▁becomes ▁und et ect able , ▁and ▁there ▁is ▁also ▁a ▁second ▁peak ▁in ▁the ▁light ▁curve ▁that ▁has ▁a ▁spectrum ▁which ▁more ▁closely ▁res emb les ▁a ▁Type   I b ▁super n ova . ▁The ▁pro gen itor ▁could ▁have ▁been ▁a ▁massive ▁star ▁that ▁exp elled ▁most ▁of ▁its ▁outer ▁layers , ▁or ▁one ▁which ▁lost ▁most ▁of ▁its ▁hydro gen ▁en velope ▁due ▁to ▁interactions ▁with ▁a ▁companion ▁in ▁a ▁binary ▁system , ▁leaving ▁behind ▁the ▁core ▁that ▁consisted ▁almost ▁entirely ▁of ▁hel ium . ▁ ▁As ▁the ▁e ject a ▁of ▁a ▁Type   II b ▁exp ands , ▁the ▁hydro gen ▁layer ▁quickly ▁becomes ▁more ▁transparent ▁and ▁reve als ▁the ▁deeper ▁layers . ▁The ▁classic ▁example ▁of ▁a ▁Type   II b ▁super n ova ▁is