The designation Sk means that Nick Sanduleak catalogued the star. The -69 is the approximate declination for the star and the 202 means that it is the 202nd star in the catalogue.

The properties of SK -69 202 are

• Luminosity ~ 100,000 L(Sun)
• Spectral Class = B3 I supergiant
• T(surface) ~ 16,000 Kelvins
• Mass ~ 20 M(Sun)
• Radius ~ 3 x 10¹² cm

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SK -69 202 is a blue supergiant whereas the typical TYPE II supernova was thought to be produced by a red supergiant. The inference that TYPE II supernovae are produced by red supergiants is based on theoretical modeling of the light curves of supernovae and numerical simulations of massive stars.

This issue was resolved rather early on when theorists noted that blue supergiants could in fact produce TYPE II supernova if some additional effects were included in the calculations. It was found that if one considered the fact that the stars in the LMC seem to have fewer heavy elements than the stars in our Galaxy and if one included the effects of stellar winds in the evolutions, then one could make evolved stars loop back into the hot portion of the HR diagram. That is, evolved stars could appear as blue supergiants!

So, although the observation that a blue supergiant exploded was initially puzzling, it turned out that such an observation was easily accomodated by theory and it, in fact, explained why the light curve of SN1987A was a little odd.

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