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How are Type Ib and Type Ic supernovae different from Type II supernovae?
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Supernova
Composite image of Kepler's Nova, or Kepler's Supernova, taken by the Chandra X-ray Observatory.
Type Ib and Type Ic supernovae differ from Type II supernovae primarily in the composition of their outer layers and the resulting spectral features.
While all three types—Type Ib, Type Ic, and Type II—originate from the core collapse of a massive star, they are distinguished by the presence or absence of specific elements in their envelopes:12
- Type II Supernovae: These stars retain their hydrogen envelope, which results in prominent hydrogen lines in their spectra.2
- Type Ib Supernovae: These stars have lost their hydrogen envelope but retain a helium shell, leading to a spectrum rich in helium lines.2
- Type Ic Supernovae: These stars have lost both their hydrogen and helium shells, resulting in spectra that lack lines for either element.2
In summary, while Type II supernovae are characterized by the presence of hydrogen, Type Ib and Ic are categorized as such because they have been stripped of their outer hydrogen layers before the explosion occurs.12