What is the fatal distance considered to be,to earth from a star supernova?

Back in the year 1054, Earth was hit by the effects of a supernova 6,500 light years away. Hardly anybody except astronomers noticed. That was the closest supernova in recorded history.

About 3 or 5 million years ago, there was a supernova 100 light years away. We can detect traces of iron-60 that it left on the deep-sea rock. That doesn't seem to have much of an effect on the plants and animals of that time.

Estimates are that a supernova would have to be within 30 light years to be a danger, and none of the 500 or so stars that close are at risk of exploding.

Generally within about 10 parsecs = 31 lightyears. However, some supernovae are highly anisotropic, sending out beams of gamma rays along the rotational axis. Such a beam of gamma rays can be lethal over much greater distances, perhaps 1000 parsecs if you happen to be aligned with the beam.

I've heard varying numbers over the years, and a lot of it depends on the size of the event and especially the direction of the axial polar jets. I've heard estimates ranging from 50 light years to 200 ly, if I recall correctly.

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