[dak1]

Anton Petrov has pretty decent coverage of this on his YouTube channel[1].

This type of supernova has been theorized, although to my knowledge not previously observed (due to the mechanics, about 50% of the energy is radiated as visible light, which is why they're so exceptionally bright).

We do have a star near us that is theorized to have undergone a pulsational pair instability supernova in the 19th century: Eta Carinae.

[1] https://www.youtube.com/watch?v=dhjHs2L4kqw

[nwallin]

Eta Carinae underwent supernova imposter events, not supernova. Otherwise there wouldn't be an Eta Carinae.