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The Question

(Submitted November 23, 2003)

I know that there are different types of supernova explosions:

  • Ia
  • Ib
  • Ic
  • II
What do these mean? Do they account for how big the explosion is?

The Answer

Thank you for your question. As is the case with most astronomical objects and phenomena, supernovae are classified according to their basic observable characteristics -- in this case particular features of their optical spectra and behavior of their "light curves" (how their brightness changes with time).

For example, the Type I (Ia, Ib and Ic) are distinguished from Type II by the absence of hydrogen spectral emission lines in the former (and their presence in the latter). In addition, type Ia are always the same mass and thus the same luminosity, which is why they are considered to be standard candles.

For more details, please see one or more of the following sites:,,,
where you can also find information on the different physical characteristics of these different types.

Most supernovae of all classification are believed to have roughly the same amount of energy released.

-- Michael Loewenstein and Amy Fredericks for "Ask an Astrophysicist"

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