How do you type a star?

Observationally, how can we tell the difference between a white-dwarf supernova (type I) and a massive-star su

• Observationally, how can we tell the difference between a white-dwarf supernova (type I) and a massive-star supernova (type II)?

• Answer:

  Hydrogen lines. Remember, long before we had much understanding of these phenomena at all, we were classifying them. Classification is the first step of any immature field of science. Once you get things into boxes, then you can start looking for common properties and begin to figure out what the heck is going on. A white dwarf SN happens when an object with very little hydrogen in its outerlayer collapses so, there is little or no hydrogen absorption in the spectrum. A massive star SN typically has a fair amount of hydrogen left in its envelope, or at least in its immediate surroundings. . . I wonder what a Wolf-Rayet star SN would look like? (IIRC WR stars have essentially blown all of their hydrogen envelopes off into interstellar space, leaving only heavier elements behind)